Construction Technology (L3) Leconfield Primary School

Question 1

What did your outline designs include?

Answer 1

• I included for a timber-frame classroom extension including of teaching space, cloakroom and storage.
• Externally, a wet pour play area with a canopy

Question 2

How did you produce your outline design?

Answer 2

I initially used AutoCAD to produce a floor plan showing the layout and space requirements. I then imported the floorplan into revit to provide a 3D model to make it easier for the school to interpret the design.

Question 3

How did you produce your budget estimate and did you make any adjustments?

Answer 3

I used an elemental rate from the previous year on a similar project adjusting for labour and material price increases and time and quality.

Question 4

What was the reason for the closure of the school hall?

Answer 4

Major structural defects to the glulam portal frame due to a lack of force resisting connections.

Question 5

What impact did the clients request have on your construction choices?

Answer 5

I had 3 construction choices:

• Traditional build: This option required a longer on-site programme and could not be completed before the start of the new term.
• Modular classroom: This option could be completed before the start of the new school term, but I had to omit this option due to restricted site access
• Timber-frame: This option was a shorter on-site programme and could be completed to the client’s request. I recommended this option as a form of construction.

Question 6

Why did you specify timber-frame?

Answer 6

• I could achieve the requested timescales made by the client
• I considered timber-frame as are more sustainable form of construction with excellent thermal performance, minimal waste, and flexibility on design.
• I considered traditional cavity walls, however, the clients requested timescales could not be achieved. The benefits of the timber frame also outweighed the benefits of the traditional construction

Question 7

What were the main benefits of timber-frame?

Answer 7

• Shorter on-site programme
• Flexible design
• Excellent thermal properties whilst remaining a narrow wall construction
• Lightweight, not requiring extensive foundations
• Excellent tolerances can be achieved due to being manufactured in a controlled environment
• Minimises potential health and safety issues due to manufacturing off-site

Question 8

What was the build-up of the wall construction?

Answer 8

• 15mm plasterboard and skim
• 25mm vertical batten for service void
• Vapour Control Layer
• 140mm timber frame structure at 600mm centres
• 120mm PIR insulation between studs
• 9mm OSB3 board
• Breathable membrane
• 38 x 47mm vertically fixed timber batten
• 25 x 50mm horizontally fixed counter batten
• 21mm Thermowood timber cladding

Question 9

What were the benefits of the timber walls being narrow?

Answer 9

• Lightweight
• Did not require extensive foundations
• Maximised internal floorspace

Question 10

What was the u-value and why was this important?

Answer 10

• 0.17 W/m2K
• Excellent thermal performance and air tightness resulting in reduced energy costs for the school

Question 11

What legislation did you refer to for the u-value?

Answer 11

Approved Document L Volume 2

Question 12

Were there any implications on time and quality?

Answer 12

• Yes, the client had requested that the works were completed before the start of the new school term. For that reason, I specified timber-frame which could achieve the timescales.
• I used 90% price 10% quality on the programme and ESP including method statement.

Question 13

What was the floor build-up?

Answer 13

• Reinforced concrete raft foundation with 150mm upstands
• 1200- gauge damp-proof membrane lapped with DPC and taped joints
• 75mm Kingspan Kooltherm K103 PIR Insulation
• Separation layer
• 75mm quick drying sand/cement screed
• 140mm timber soleplate is mechanically fixed through the DPC and into the 150mm concrete upstand. Holes created through DPC are beaded with silicone to prevent moisture transmission into the timber

Question 14

Was the raft foundation reinforced; what was the reinforcement detail?

Answer 14

• To prevent cracking and provide flexibility
• Strength the up-stand for the timber-frame wall
• Consulted with a structural engineer for the design

Question 15

What were the existing ground conditions?

Answer 15

• There were no issues with the existing ground
• Trial holes had been dug as part of my initial investigation

Question 16

Did you design the foundations?

Answer 16

I consulted with a structural engineer to ensure the raft foundation was designed accordingly forming a 150mm up- stand for timber-frame walls to be mechanically mounted.

Question 17

What was the connection detail for the raft foundation up-stand and the timber walls?

Answer 17

A 140 x 38mm timber soleplate was mechanically fixed into the 150mm concrete up-stand using threaded rods fixed with a resin compound. Any penetration to the DPC was sealed with a sealant.

Question 18

Why did the raft foundation minimise time and cost?

Answer 18

Less excavation was required resulting in less earth disposal.

Question 19

How did the timber-frame building connect to the existing building; did you account for thermal movement and settlement?

Answer 19

A DPC was laid vertically beneath a timber soleplate which was fixed directly into the existing walls using mechanical fixings. A slot was created to allow the timber-frame to move independently from the existing building.

Question 20

What was the outcome of the completed works?

Answer 20

The scheme was completed within budget, to programme and a completion certificate was issued by Building Control for compliance.