Case Study - Harley Terrace Flashcards
(162 cards)
1
Q
What CA duties did you carry out?
A
Chair meetings, issue instructions, progress/quality inspections, value/issue payments,
2
Q
What BS duties did you carry out?
A
Identified what elements were at their end of life.
Determined what elements had failed.
Carried out inspections.
3
Q
What Designer duties did you carry out?
A
designed and specified the works.
I reviewed the Building Regulations A, B, H, L etc.
I liaised with the PD and PC and supplied information.
Provided client with HSE CDM guidance note on their responsibilities.
4
Q
What did the initial consultation with the client cover?
A
Budget, quality expectations and programme.
Established their needs/requirements for the works.
I advised of the next steps (i.e. project brief, preliminary site inspection, feasibility and option appraisal)
5
Q
What did the strategic brief cover?
A
Objective – Repair and refurbishment.
Stakeholder requirements – To good quality.
Functional requirements – Make good all known defects and modernises the property.
Specialists needed: SE and Asbestos Surveyor
6
Q
What did the Project Brief cover?
A
Client information.
Site information -Drawings, Asbestos Survey
Technical requirements – Party Wall, B Regs, CAR. CDM
Component requirements – Specified sanitary and wall tie (Redifix system)
7
Q
What was the client’s initial requirements?
A
Repair works and modernisation to parts internally.
Wanted to open rear hallway wall – not feasible.
Client favoured quality.
8
Q
What was the clients budget?
A
£35K
9
Q
Was the works notifiable to Building Control and Planning?
A
Building Control – Yes.
Wall ties works, sanitary refurbishment.
Planning – No.
10
Q
Was any other provisions of Statute applicable?
A
CAR 2012
Party Wall etc Act 1996
CDM 2015
11
Q
What did the outline design include?
A
The general scheme i.e. what works to be carried out.
12
Q
What did the technical design include?
A
- Nominated materials (sanitary ware etc) and systems.
- Incorporated the SE’s recommendations.
13
Q
What wall tie system did you specify? And what others are you aware of?
A
Redifix system was specified with a mechanical fix as this was suitable as the inner leaf substrate was robust. If weak/friable a resin fix would have been used.
These torque/mechanical ties are inserted into the drill holes. The ties are wound up and they expand to grip the masonry.
14
Q
What procurement method did you undertake?
A
Traditional, client wanted cost assurance at that stage.
15
Q
How did you select a contractor?
A
Tender analysis.
16
Q
Which contractor’s did you send the tender pack out too?
A
4nr contractors who had CHAS and Constructionline accreditation. All selected from our approved contractors list.
17
Q
What was included in your feasibility study?
A
Clients requirements Study findings Statutory requirements Option appraisal Recommendations.
18
Q
Was the Pre-construction information pack part of the tender document?
A
Yes – completed by the PD.
19
Q
What’s included in PCIP?
A
Project information
Key contact details
Site information
Known hazards etc.
20
Q
How did you analyse the tender’s?
A
Tender analysis table comparing each tenderer against any irregularities.
21
Q
Why did you come to a decision about utilising a MW?
A
I considered the JCT Homeowner contract; though, after discussing the choices with the client they expressed they wanted more control procedures as the Homeowner Contract doesn’t have a provision for LaDs and the retention/rectification period is different.
Intermediate/standard was considered with the Named Specialist provision but the standard contracts mechanisms wouldn’t have been proportionate for the works and excessive.
22
Q
How was your services agreed?
A
Terms of engagement letter was prepared and signed which specified the services, fee, limitations, PI, CHP etc.
23
Q
How did you establish the stakeholder’s?
A
I brainstormed who would be affected, have an influence of had an interest in the works.
- Client
24
Q
What were the effects of COVID on the programme?
A
Pre-construction – delayed the design phase and clients sanitary selection due to shops being closed.
Construction – Contractors programme extended by 2 weeks to account for additional health and safety on site.
25
How did you promote Health and Safety during the project?
Designer responsibilities CDM!!
I provided them with the HSE's Clients Responsibilities CDM document.
Cooperating with others involved with the project and provided information.
Carried out site inspections.
Designers risk assessment (i.e. scaffolding to be used, no smoking, no radios etc)
Social distancing.
26
What periods were the interim payment dates and why?
4 Weekly – although not necessary in accordance with construction Act this is standard practice for small works and fair to the contractor.
27
How did you monitor progress?
Monitored works on site against the programme to ensure the date for completion would be hit.
Weekly inspections and inspected at critical periods.
28
What was the client's vision?
I drew key information from discussions, this included that they didn’t want the repair works to be obvious to the repaired bulging wall in the event they wished to sell in later years.
29
How did you establish the clients funds?
Customer due-diligence by ID Checks and address verification.
Simplified due-diligence wasn't suitable due to quantum of works and Enhanced due diligence wasn’t needed in these circumstances as I established there wasn’t a high risk of money laundering activities.
30
How did your contract selection offer a suitable agreement between parties?
- Transparent (both parties knew what was on the table)
- Standard form of contract (JCT) both client and contractor aware of these.
- Only obliged for what could be paid for.
31
Did you consider an Intermediate Contract?
Yes but the control procedures were some what extensive for what was needed.
However, the named specialist feature would have been beneficial.
32
In the event of Contractor Liquidation, if you’ve been contacted by a third party (Administrator/Liquidator) to recover the Contractors funds/plant/items following liquidation – should you pay them what they ask for?
Essentially, the answer here is no. (6.7 of Contract)
Wait until the works are complete, upon which you prepare a statement of the expenses incurred in completing the works.
This includes making good any defects, plus the costs of site security and safeguarding materials, plant and equipment on site.
You will also need to add the cost of any loss or damage due to the contractor’s insolvency or a result of their termination.
Once you have the statement of expense, this is added to the amount paid to the contractor to date and compared to the original cost of the package of works. It is almost entirely the case their expenses plus the cost to date will exceed the original package of works value.
33
Are there any other ways to guarantee non-insolvency of a contractor?
Cannot guarantee.
- Check previous and current accounts, credit check etc.
- Take out a performance bond or parent company guarantee.
34
How are Liquidated Damages claimed for?
They're taken off the Final Payment by the means of a Pay Less Notice by the client or recovered as a debt.
The LaDs in my case study were £50/week storage costs for the clients furnishings.
35
Why was the tender period a Traditional route?
Client wanted cost/quality certainty.
36
If a contractor made a mistake in a tender, what would you do?
Alternative 1: Ask them if they wanted to stand by cost or withdraw.
Under Alternative 2 they're allowed to amend.
37
What could you have done better on this project?
Invasive investigations earlier which would have allowed a more in depth diagnosis; however, at the direction of the client these were undertaken on site.
38
How long does the contractor have to submit their final account and documentation following PC?
Usually within 3 months of the contractor obtaining PC or as specified within JCT contract.
Due date is 28 days after receiving all documentation.
39
Why did you select Adjudication in the contract?
In accordance with the construction act. everyone has a right to adjudication (its statutory).
It's quick, cheap and binding until the contract has been completed.
40
If you wanted to instruct a consultant or engineer directly, how would you do this?
I would always advise they go directly with the client, to minimise liability.
However, there is a sub-consultancy agreement which requires the consultants to ensure my firms procedures and processes are adhered too.
41
What level of insurance did the contractor carry?
£10m public liability
£10m employers liability
sufficient for the works.
42
How was CDM managed during the project?
By appointed PD and PC.
| I carried out designer duties throughout the works.
43
Why didnt you carry out the PD role?
It's a company policy where the CA cannot act as the PD as this acts as a QA process.
44
Tell me about the WC below the stairs?
Drainage was the key issue, used doc H.
Considered gravity drainage or a mechanical macerator system.
Extract system also tricky as needed to box in the duct work through the kitchen.
45
What was included in your drawings, spec and SofW?
Drawings – floor plans
Spec – Overview of the works
SofW – Detailed schedule of the works.
46
What wall tie system did you specify and why?
Redifix Mac Tie Remedial – Recognised product, conforms to British Standards.
Mechanical system was suitable as inner leaf was masonry and was in good condition.
Mechanical system is an expansion system where the tie is torqued and expands into the drill holes to get a grip.
47
What damp proof repairs did you specify and why?
Sovereign Injection Cream – 20-year warranty, fit for purpose and BBA approved.
Specified to inject the DPC below the joists in accordance with BS 6576 and the manufacturers recommendations. Reason why: to prevent deterioration to finishes (skirting/low-level plaster). However, the injection was not necessarily needed to be installed below the floor joists, specifically for the joists as they were supported by sleeper walls and had no contact with the affected walls. Therefore the timber joists could not be affected by rot etc. Joist ends were checked, in ok condition and were left.
Sovereign Render Lite plaster was used as the plaster is breathable and effective moisture barriers as required by BRE Digest 245. In addition, Sovereign advise this is suitable following an injected DPC as the system contains salt retardants. This is important as standard plasters may actually draw the salts into them allowing moisture to reform. System was also permeable; though, resistant to liquid moisture.
48
Why was it a 12-month rectification period?
To monitor the works over an entire season.
49
How did you establish the client prioritised quality over cost and time?
I drew this information from discussions with the client.
50
Why wasn’t the JCT homeowner contract suitable?
Client wanted more extensive control procedures appose to the homeowner contract which has (2 parts)
Client wanted:
LaDs - not included in homeowner
More robust rectification period (only 3 months in homeowner)
More robust control procedures as Contractor needs to notify of delays etc.
51
Who recommended the 5-week programme?
The contractor.
52
How did COVID-19 affect the project?
Pre-construction: Furlough delayed design phase and client was unable to look for sanitary ware in shops as they were closed.
Construction phase:
Programme initially extended by 2 weeks to account for more extensive health and safety on site. Social distancing, Hand sanitising, Face coverings etc.
53
Key issue 1: How did you diagnose the rising dampness and what else did you consider?
Initial preliminary non-invasive investigation (clients request) with a moisture meter:
- Tide marks/readings to the wall – moisture content was approx. 25-50%. (Plaster is usually around 10% when dry)
- Damp and musty smell.
- Salt deposits to the wall.
- Blown internal finishes were identified.
Note: The timber joist ends of the ground floor weren’t in contact with the walls as they were supported by a honeycomb sleeper wall arrangement.
Other considerations (Rejected):
- Condensation considered; though the relative humidity was reasonable at 55%. Staining only around chimney walls etc. and the chimney was well vented by a pot/cowl and floor vent.
- Penetrating dampness from chimney – checked with drone and no dampness to bedroom above which you would expect to see.
- Penetrating dampness from the air brick; though, was 150mm above ground level therefore ok.
- Client advised boiler pressure hasn't lowered indicates no failed radiator pipework.
Secondary: Invasive on site during the works with a speedy carbide test, which subsequently exposed the earlier injected DPC.
- Identified walls were damp by visual characteristics and when tested contained 10% content of a total of 20 as per the carbide vessel meter.
- Advised the client that Lab testing would be the next stage to determine if hygroscopic salt content but they were happy to proceed on my findings.
54
Key issue 1: Why did you only recommend injecting 1 leaf of the of the cavity party wall?
Cavity wall construction therefore injecting 1 side wasn't decremental.
Had the wall been solid it would have been necessary to inject the neighbouring side too or provide permeable/breathable materials.
55
Key issue 1: How had the earlier retrofit DPC injection failed?
The main issue was that the earlier DPC wasn't to a sufficient depth which allowed moisture to pass through.
When undertaking works to a single leaf, the drill must completely pass through the mortar course.
56
Key issue 1: Where had the earlier DPC failed?
To the wall within vicinity of the chimney.
57
Key issue 1: How does a chemical injection work?
Holes drilled at intermediate centres, the cream is injected and this then forms together under the mortar creating a damp-proof course.
58
Key issue 1: Who was involved in the site meeting?
Me, Employer and Contractor.
59
Key issue 1: How long did the guarantee have left on it?
4 years.
60
Key issue 1: How did you establish the guarantee wasn’t insurance backed?
Usually it would reference who its backed by within the document and it did not.
61
Key issue 1: Tell me about the effects of Cost Quality and Time in relation to the options considered?
Quality – appointed contractor to rectify w/ guarantee. Quality couldn’t be assured from earlier contractor.
Time – appointed contractor to resolve immediately. Time couldn’t be assured from earlier contractor.
Cost – additional costs incurred if appointed contractor to resolve. Costs could be saved if earlier contractor resolved.
62
Key issue 1: Why did you think negotiations would take long with Option 1?
Client had previously spoken with them and advised that they didn't intend to upkeep the guarantee.
I spoke with them and they were being very vague and uncooperative.
63
Key issue 1: You mention Critical Path what is this and what was on the Critical Path in your project, how was it affected?
Critical path- any works which are critical to progress and if they’re affected so is the date for completion.
Site setup and welfare was critical. The repairs did have critical items though none were fundamental for progress.
64
Key issue 1: How do you issue an Extension of Time and what contract mechanisms does this release?
EoT certificate, changes date for completion and insurers need to be notified.
65
Key issue 1: What are prolongation costs?
Costs incurred due to the contract period being prolonged – could include management costs, plant costs, welfare costs etc.
66
Key issue 1: Why was the earlier contractor not being locally recognised a risk?
```
Quality risk (ongoing issues, problem not resolved)
Health and safety risk – CDM.
```
67
Key issue 1: Why would the formation of a joint create a weak point?
Bonding issue between a ‘cured’ installation and a fresh install as an abutment joint would be formed thus creating a weak spot.
68
Key issue 1: Tell me the extent of the immediate dampness within the lounge and where did the earlier and new works cover?
Damp was present to the wall within vicinity of the chimney and the chimney cheeks.
The earlier damp works covered the party wall and front portion.
The new works covered the entire lounge.
69
Key issue 1: What would be the repercussions of Employer Related Delays?
Prolongation related costs such as additional management fees, plant, welfare etc.
Duration of the works extended.
70
Key issue 1: What effects did the variation to remove the earlier DPC have on the contract?
Additional time and money (extension granted)
71
Key issue 1: Why was the plaster kept off the ground?
Reduce contact with the masonry wall standard practice and this allowed the timber to be dry during the drying out phase which prevented rot or woodworm.
72
Key issue 1: Where was the injected DPC installed?
Below the joists.
73
Key issue 2: How did you diagnose the wall tie failure? What else did you consider?
Displaced walls, lifting bed joints/horizontal cracking, cracked window jambs, broken/displaced cavity closer course internally.
Lateral forces from the roof or floor structure were considered initially, perhaps due to failed fixings.
74
Key issue 2: What original wall ties were fitted?
Twist/fish tail ties which had a large mass and could expand/corrode further if left.
75
Key issue 2: What would have been the repercussions of further expansion if the wall ties were left in place?
Physical loss – damage to building.
Financial loss – additional repairs needed.
Reputation – RICS, BSL etc.
76
Key issue 2: How did you calculate the provisional sum for the repair works?
Based my calculation on a day rate for the envisaged works (I.e. worst case)
77
Key issue 2: How did you allow the contractor to expend the sum?
Contract instruction omitted the PC sum and added in the new sum for the works.
78
Key issue 2: Did you use an approved document for the rebuild – tell me about it?
```
Approved document A
900mm horizontal spacing
450mm vertical spacing
Modern stainless-steel ties
Staggered
No more than 300mm vertically at openings
```
79
Key issue 3: What’s the difference between the Date for Completion and the Completion Date?
Date for completion = envisaged complete date in contract
| Completion date = actual date the works are complete
80
Key issue 3: Was the client allowed to informally nominate their own supplier? What would be the consequences/risks with this?
No there’s no formal provisions in the MW contract.
There is a named specialist provision in the JCT Standard contract, but the contract would have been extensive for the works.
Could have wrote into SofW.
Risks
1. Employer related delays, quality issues, cost issues as contractor may be able to obtain cheaper and benefit from profit.
2. If contract prolonged this exposes the client to Loss/Expense / extensions of time – the client should seek to obtain an indemnity from the supplier in advance in the event this occurs.
3. Poor performance (who’s responsible for this?)
81
Key issue 3: Why was the sanitaryware late?
Cargo ship was unable to port due to COVID19. I established this with the supplier and considered that this was neither the contractors fault nor the employers.
82
Key issue 3: What contract mechanisms would PC release?
Half the retention.
Employers takes back the site and insurers. (Relives the contractor)
Rectification period begins.
End of Liquidated damages
83
Key issue 3: Why was proportionality a key concern?
It’s a part of PACCT – All RICS members are expected to act proportionately to there area of practice.
84
Key issue 3: What’s the risks of a pre-mature defect liability period/issuing PC to early?
Contractor may lose interest which could be significant if there’s defective works.
PC signifies that the works are ‘complete’, could be acting negligently if this is issued.
Negotiation power reduced with the contractor.
Unable to claim liquidated damages.
Cannot remove the contractor from site under non-performance as works have hit PC.
85
Key issue 3: What could you do if there were outstanding works to complete in the defect rectification period and the contractor wasn’t interested?
Submit notice to rectify, failing this can instruct a second contractor to resolve and either deduct from contract or claim back as a debt by a pay-less notice if exceeded.
86
Key issue 3: Was there any Liquidated Damages on the contract, how were these calculated?
Electrical costs for additional electrics needed from the contractor. £50.00p/week.
87
Key issue 3: Difference between Relevant Event and Relevant Matter?
Relevant Event – Event causes the date for completion to be pushed back, may entitle the contractor to EoT.
Relevant Matter – Event caused by Employer which pushes back the date for completion, may allow the contractor to claim loss and expense.
88
Key issue 3: How was the late delivery not the contractors fault?
Employer informally nominated them.
89
Key issue 3: How was the late delivery the employer’s fault?
They informally nominated the supplier; although, it was established the delay wasn’t caused by either party as COVID caused the delayed delivery, though the employer held some blame.
90
Key issue 3: When did the delay arise and when did you know about it?
Mid-way during the project and quite early. Contractor advised me accordingly.
91
Key issue 3: How did you issue an Extension of Time?
Formally by a certificate which alters the date for completion. Insurers notified accordingly.
92
Key issue 3: What other issues warrant an Extension of Time?
Variations
Adverse weather
Force majeure
Failure for CA/Employer/Architect to provide info.
93
Key issue 3: What issues warrant Loss and Expense, i.e. relevant matters?
Delays caused by the Employer.
Opening up works / testing
Claims are restricted to direct loss, so plant, management, staffing etc.
94
Key issue 3: Why was a 2-week EoT reasonable?
Required by the contractor to re-schedule in plumber and to take delivery.
95
How have you demonstrated one of the 5 Global Professional and Ethical behaviours in the project?
Integrity – Avoided conflict of interest by not carrying out party wall services.
Respect – treat everyone with respect.
Responsibility – Acting as the lead consultant I took responsibility for the project.
High level of service – Appoint SE to provide high service.
Promote trust in the profession – Do what I said I would do by meeting the clients requirements.
96
How was the SE and Party Wall Surveyor instructed?
Direct appointment with the Employer.
97
Why is being impartial as a CA critical?
Administering the contract and act impartially between Employer and Contractor.
98
Could the contractor had used their own supplier under the terms of the contract?
Yes – contractually they were able too; though to conform with spec they were unable too.
99
Was the client able to formally nominate their own supplier under the JCT MW?
No.
Yes under JCT Intermediate/standard by 'Named specialist' provision.
or
by stating in SofW.
100
Are there any contracts that allow the client to nominate their own supplier?
Named specialist in JCT Intermediate and Standard.
Could also nominate in SofW if the supplier was known during that stage of the project.
101
How else could the client had formally nominated their own supplier? What’s the risks involved with this?
Client to provide materials.
If too little materials bought – could result in employer delays.
Insuring the materials?
Risk of liquidation of nominated supplier (Quistclose trust)
Performance - late deliveries?
State in SofW to nominate selected supplier.
Utilise named specialist provision.
102
Photograph 3 – When was this taken and tell me about it?
Following the works – walls stabilised.
103
If the contractor nominated their own supplier and the delay had occurred what would have been the process you would have taken?
If the contractor has tried to obtain the materials from other suppliers and were all experiencing delays because of COVID19, this would have been a force majeure event and EoT granted.
It would have been likely that the contractor would have been able to obtain from elsewhere.
104
Why wasn’t Key Issue 3 a relevant matter and allowed the contractor to claim for loss/expense?
Current standpoint that due to COVID-19 Employers and Contractors should aim to work together where possible if delays occur due to covid-19.
Contractor was able to leave site with welfare facilities etc and return to execute outstanding works without any facilities.
105
Why did the Employer want to specifically use that supplier?
Prior relationship.
106
Key issue 1: What did you initial investigations entail and what other investigations did you carry out?
Initial investigations: Initially non-invasive as per clients request as finishes were in situ, I identified tide staining/moisture content to the wall which indicated rising dampness.
Further invasive investigations during the project with the contractor exposing the walls included checking the sub-floor void which revealed:
1. No service leaks in sub floor from radiators etc.
2. The cavity wall wasn't bridged.
3. The original felt DPC had become brittle with age.
4. The earlier injected DPC revealed to be of poor workmanship and failed.
During the opening-up works a carbide test was undertaken.
107
Key Issue 2: How does wall tie failure occur?
A wide variety of ties and mortars are susceptible, combined with age, climate and environmental exposure.
As the mortar ages, alkalinity is reduced by the absorption of atmospheric carbon dioxide (carbonation). The presence of chlorides or sulphates in the mortar mix speeds up the passive layer breakdown and removes any protective coating to the metal.
Zinc/galvanised coatings fail as the standards were defective in earlier years.
Moisture then enters cavity by either porosity of the masonry or by failures etc.
This corrosion results in extreme expansion of the steel tie.
108
Key Issue 1: What are Hygroscopic Salts?
Hygroscopic salts contain Nitrates and Chlorides which are usually from groundwater or from fossil fuels (timber, gas, coal etc).
These salts are 'Water attracting' salts which will draw water from the air, materials or ground.
These are usually left behind from earlier rising dampness issues when the dampness have evaporated.
The salts are absorbed into building materials such as plaster and can attract water casing further issues.
These salts will create false readings in moisture meters.
109
Key Issue 1: What are Hygroscopic salts made up of?
Nitrates and Chlorides
Can be sourced from ground water usually or can be sourced from fossil fuels (coal from stove).
110
Key Issue 1: Why can a tide mark/moisture content be misdiagnosed?
Due to left of Hygroscopic salts left on the wall creating a salt band replicating the tide mark from earlier rising dampness.
111
Key issue 1: How do you carry out a speedy carbide test?
1. Drill into wall and obtain sample.
2. Weigh 6g and put into vessel with 2 scoops of calcium carbide.
3. Shake and wait 15 minutes to react.
4. If moisture is contained within the sample,/specimen the vessel will produce gas and pressurise the vessel.
5. If there's a reading of above 5% in walls its damp.
112
Key Issue 1: What is hygroscopic testing and did you consider it?
Hygroscopic testing is the second phase of a speedy carbide test by laboratory testing. Or it involves taking samples/testing samples initially recording there content and putting other samples in a 75% humidity enclosure for 48hrs, this will then determine the true moisture content which were were influencing test results.
Testing recommended but client happy to proceed due to not wanting to delay the works and because of the characteristics observed, was likely rising dampness. I advised if this was solely hygroscopic salts, the repair method in plastering wouldn't differ and the only unnecessary cost would be the chemical dpc which was minimal costs involved.
113
Key issue 1: What are the advantages/disadvantages of a moisture meter?
Advantages:
- Non invasive
- Good indication of moisture content in materials
- Quick
Disadvantages:
- May give false readings of moisture pockets and hygroscopic salts.
- Only calibrated to timber but can give good indications of other materials.
- Lead paints etc may obscure readings as these paints etc. conduct electricity.
114
Key issue 1: What are the advantages/disadvantages of a speedy carbide test?
Advantages:
- Accurate results.
Disadvantages:
- Invasive and will cause damage.
- Need to determine hygroscopic content to definitively confirm rising dampness. This is usually done by lab analysis or controlled testing.
- Take long - about 15mins per sample.
- Gas is hazardous/flammable.
115
Key issue 1: What BRE digest relates to diagnosing rising dampness?
BRE 245.
116
Key issue 1: What methods of repair were available?
1. Install a physical DPC (Best option).
2. Install chemical DPC w/ Guarantee. Main drawback is that the brick course needs to be regular (i.e. no voids/penetrations) for it to work.
3. Mask the walls with lining or a tanking system (this is suggested by BRE). - Disadvantage to this is that the dampness will likely rise further and may cause further degradation.
117
Key issue 1: Why was specifying the correct plaster important?
The wall should be able to dry out so permeability is a key concern. If the wall cannot dry out, hygroscopic salts could lay on the plaster when drying out, which may lead to water being retained or attracted to plaster causing further degradation.
Usually takes 6 months but Sovereign recommends a specialist plastering system which is:
- Salt resistant
- Liquid moisture resistant
- Permeable (allows wall to breath and dry out)
- Can be undertaken 14 days after chemical DPC injection.
118
What questions did you ask during the briefing stage?
Budget?
Timescales?
Standard of spec (i.e. low, medium or high spec/finishes?
119
What did the brief include?
Budget.
Component requirements (Clients chosen sanitaryware)
Technical requirements - SE Required.
Site information - Asbestos report.
120
What procurement method did you undertake and why?
Traditional method, client wanted cost and quality certainty.
121
How did you identify the client prioritised quality?
Had a decent budget for the works.
| Drew key information such as the materials they proposed and there take on the appearance of the repair.
122
Key issue 1: Why were only the lounge walls subject to rising dampness?
The felt DPC had failed in localised areas, other areas checked and I identified the DPC was bridged which was later cleaned/unblocked.
123
Key issue 1: How had the original and earlier injected DPC in the lounge failed?
Original felt DPC was brittle in localised areas.
Retrofit: Not uniform, patchy and looked insufficient.
124
Key issue 1: Why wasn't a physical DPC suitable?
I recommended the option to the client; though, the cost and disruption was outweighed by the more convenient chemical injection which was guaranteed.
125
Key issue 1: Where was the earlier chemical installation installed?
It was within the sub-floor void which was a small depth, due to this it required removing to be able to suitably install a new system.
126
Key issue 1: Why wasn't tanking/dry-lining suitable?
It was considered; though, given the earlier DPC had failed and was irregular. I was confident that a new injection would be suitable.
127
Key issue 2: Why do you think the contractor didnt want to accept liability?
Costly and disruptive to them.
They were being short on the telephone, weren't cooperating saying that they weren't able to attend for months etc.
128
What works formed part of the Critical path?
The welfare and site set-up were the only critical item as this was the only item which really affected progress. However, each of the small works had their own critical items in some respects.
129
Key issue 1: Why was is necessary to remove the earlier DPC?
Due to the sub-floor depth and that there was only really one suitable course to inject which was already occupied by the earlier installation.
130
Key issue 2: How could further corrosion occur?
Masonry is porous and in turn will allow moisture to enter due to this. This may have led to further volumetric expansion.
131
Key issue 2: How do wall ties corrode?
1. Zinc coatings in pre-stainless steel ties degrade over time which then expose the ties to corrosion.
2. Carbonation occurs to the mortar which reduces the alkaline which protects the ties from corrosion. Corrosion then may occur.
132
Key issue 2: How were the retrofit ties fixed?
Mechanical fixing - suitable when inner leaf materials are solid/hard.
Resin fix - suitable when inner leaf material are friable and weak.
133
Key issue 1: Is there any ways to remove Hygroscopic salts from walls following rising dampness?
Only feasible way is to re-plaster with specialist salt resisting plasters.
or by allowing to dry, remove salts cycle, very long and would be costly.
134
Key issue 3: How was the sanitary supplier 'Informally' nominated?
By an agreement between the Employer and Contractor.
Contractor was already appointed before the client selected the sanitary ware, therefore contract was already signed with SofW etc. The sanitary ware was priced by a PC sum in the tender stage.
There was a written record of the nomination and the contractors agreement for an audit trail.
135
Key issues 3: Are there any court cases which relate to an epidemic event?
Lebeaupin v Crispin [1920] - confirmed an epidemic would be a force majeure event. Accordingly, delay caused by COVID-19 would give rise to an extension of time.
Citrus Soap v Peet Bros - confirmed Spanish flu was a force majeure event.
It's my understanding that courts are still to decide on covid-19 regarding EoT, delays, loss/expense etc. and that people are being told to work together.
136
How was the Structural Engineer appointed?
Direct engagement with client. I met with them on site to discuss the project and indicative requirements. They then provided their own terms/fee proposal to the client.
137
Key issue 1: Did you consider condensation?
Yes I considered condensation from the chimney due to inadequate ventilation, water vapour could condense in the stack when used which could cause water droplets to run down the stack.
I used a humidity meter which identified the RH to be 50%.
To fully test you must use data loggers to show the internal and external surface temperatures. Monitor these for x weeks which will reveal the relative humidity, (if 100% is found is condensation and provide ventilation)
138
Key issue 1: What happens to Hygroscopic salts when relative humidity reaches around 75%?
Hygroscopic salts can sometimes turn into liquid form creating physical dampness and can be sometime misdiagnosed.
139
Key issue 1: How could the DPC have been bridged?
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Bridged cavity by snots, fills etc.
Raised ground levels.
Over pointed DPC.
Concrete floors bridging DPC.
External renders bridging DPC.
Plaster bridging DPC.
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140
Key issue 1: How do hygroscopic salts occur in walls?
They're predominantly found in ground water; however, they can be found by burning fossil fuels such as coals and timber (i.e. wood burners etc)
When water evaporates they crystallise onto surfaces of the materials.
141
Key issue 1: Did you check the drains?
Yes the drains were checked there were no issues, the drains were located to the rear of the property far away from the defective area.
142
Key issue 1: Tell me about low-level wall plinths?
Used during Victorian period to mitigate splashback and driving rain.
Plinths should be breathable and shouldn't bridge the DPC.
Problems arise if they aren't breathable as moisture is trapped which could lead to dampness internally and degradation / decay.
143
Key issue 1: Tell me about felt bitumen DPC's?
Old method, generally these felt bitumen dpc's were brittle when laid and could crack pre-maturely.
Movement within structures will then cause DPCs to crack.
144
Key issue 1: What happened when the appointed contractor removed the previously failed DPC?
The mortar joints were repaired, left to cure and injected with the Sovereign injection cream.
It was suitable to remove the earlier injection as it was very sporadic and to an insufficient depth which allowed the contractor to easily remove.
145
Key issue 1: How do you separate damp treated walls from sound walls?
By the use of a vertical injected DPC.
146
Key issue 1: How/where did the contractor remove the failed injected DPC?
Earlier silicone resin DPC cut out and removed to enable a new full continuous band to be installed.
As the earlier DPC was only drilled in a couple of inches the removal of the earlier installation was quite simple. Had the works been more excessive it would have been beneficial/more appropriate to install a physical membrane.
147
Key issue 1: When the earlier DPC was removed did you consider a physical DPC appose to an injected DPC?
Installation of a physical DPC requires:
- Good access to remove and re-lay a course of brickwork with the new DPC. As only removing the bed joint can be tricky and awkward which usually requires access to both side of the wall, therefore it was not suitable for the Party Wall.
- Works are usually disruptive to this part of the property and given it was a party wall the client wasn't comfortable with the idea.
- Takes longer as replacement is carried out in parts i.e. (expose the masonry in parts, install DPC, allow to cure and redo until complete)
As the earlier DPC was only drilled in a couple of inches and was very sporadic, the removal of the earlier installation was quite simple.
148
Key issue 2: Why did you recommend to remove the original wall ties?
The original wall ties were twists/fish tails and therefore had a large mass and could be able to further expand and corrode.
If the wall ties were a wire or butterfly it would have been suitable to leave them in place due to not having a large mass.
The inner portion of the wall ties were corroded and it was required to remove these.
149
Key issue 1: Did you consider a physical DPC to replace the earlier installation?
Yes I did - if the earlier works required more extensive removal works it may have been suitable to install a physical DPC. However its tricky to purely install when a bed is exposed due to needing to bed the backside of the brick. When there's access to only one part of the wall, this requires the removal of brickwork, to bed the new DPC and brick.
This method also takes longer due to starting and stopping by replacement in parts.
150
Did the Construction Act apply to your Project?
No - Client was a Residential occupier.
The implications were that there was no right to adjudication, performance suspension or payment terms etc.
151
Key differences between Homeowner and MW?
- In MW, the Contractor must notify CA if they're unable to meet the date for completion, in Homeowner they dont need to notify.
- In Homeowner, full retention released after 3 months, whereas MW is half retention then other half after rectification period.
- In Homeowner there's no provision for LaDs.
152
Key issue 1: What was your initial thoughts about the dampness?
Initially I thought it may have been water ingress via bridging, splashback through the void.
Condensation to chimney unlikely as throughout the living room masonry walls.
153
Key issue 2: What defective characteristics did you identify to diagnose the wall tie failure?
Bulging wall
Cracked window jambs
Horizontal cracking
Split header course at the cavity where the masonry was tied together.
154
Key issue 2: What else could you have done instead of removing the existing fish tail ties?
Cut them back and sleeve the ends to allow them to corrode.
155
Key issue 2: How did you know the wall tie replacement was successful?
The contractor tested the ties with a test ring/pull system which determines if the walls have a suitable bond and have reached their desired level of tension.
156
Key issue 2: Why were the ties removed?
Corrosion was present to the inner leaf and it was therefore essential.
It wasn't suitable to utilise sleeves due to the extent.
157
Key issue 2: How/where were the remedial ties installed?
Fixed through the masonry.
158
Key issue 2: What are the BRE Documents relating to wall ties?
BRE Digest 401 and BRE Digest 329.
Table included within the Digest 401 which describes the stages of corrosion and the recommended remedial options such as monitor, replace etc.
159
Key issue 1: On a speedy carbide meter what is the usual moisture content of standalone hygroscopic salts?
Usually around 3%.
160
Key issue 1: Is rising dampness seasonal?
Yes entirely. As water tables increase/rise in winter, rising damp will worsen due to those increases.
161
Key issue 1: What is gravimetric testing and how do you do it?
Gravimetric testing is the final stage (following carbide test) to determine free moisture of a material.
1. Take sample and weigh to determine full weight.
2. Put into 75 RH degree furness to dry out free moisture, weigh again to determine if free moisture was applicable. If lesser it is.
3. Put into a 30oC oven over night to dry out hygroscopic salts, weigh again to determine salt content.
162
What accreditations did the approved inspector have?
Registered with RICS and CIOB.
| Registered with CICAIR (Approved inspector register)
