Construction Technology

Question 1

What is the size of a brick?

Answer 1

215mm wide, 65mm high and 102.5mm deep.

Question 2

Can you talk me through how a steel framed building is constructed?

Answer 2

1. Foundations - ground conditions will determine the type used, however, these are usually piled and capped.
2. Steel columns are fixed to the pile cap / concrete slab.
3. Steel skeleton frame formed using universal columns and beams. This frame takes the load.
4. Permanent shuttering in the form of profiled metal sheeting make up the deck of the floor levels and is filled with cast in situ concrete forming the compartment floors.
5. Normally light gauge steel studs form infill walls, weatherboard is attached externally and will carry a rainscreen or similar.
6. Insulation envelope formed by insulating between light gauge steel studs.

Question 3

What is the size of a common block?

Answer 3

440mm wide, 215mm high and 102.5mm deep.

Question 4

What types of flat roof are you aware of?

Answer 4

• Built up roofing -usually two layers of mineral felt, fixed with hot bitumen and rolled onto substrate. Can get one layer reinforced felts.
• Asphalt roofing - It consists of a graded limestone aggregate, bound together with asphaltic cement (i.e. bitumen), heated to 210 degrees C and applied by qualified installers with a wooden float. This is mixed and applied on site.
• Single ply - Consists of a single layer of membrane composed predominantly of synthetic polymer. Can be fully adhered, fully fastened or loose laid and ballasted e.g. with gravel.
• Liquid roofing systems - Monolithic, fully bonded, liquid-based coating with a rubberised finish.
• Profiled metal sheets - e.g. fixed through purlins on commercial buildings.
• Sheet metal - e.g. copper, lead or zinc.

Question 5

What type of render system did you specify for the coastal property you mentioned in your submission?

Answer 5

I did not feel I had the necessary expertise to specify a render for this job. As a result I met with a technical representative on site and explained my requirements and talked through the job.

The specialist then provided me with a spec for a fibre reinforced polymer render which was non-degradable and crack resistant.

Question 6

Can you explain cavity construction to me?

Answer 6

• Outer leaf usually of masonry.
• Cavity of 100mm, can be partially insulated. Full insulation not recommended in Scotland due to exposure.
• Inner leaf of block normally.
• Internal linings - usually plasterboard on straps or dot dabbed.
• DPC minimum 150mm above ground

Question 7

Can you explain traditional construction to me?

Answer 7

1. Typically built on “footings” and not foundations in the modern sense using material that was at hand.
2. Walls are typically 600mm thick.
3. External leaf can be in stone or brick. Usually tied together by through stones and pre-determined points.
4. Cavity is filled with rubble and lime.
5. Inner leaf is typically brick with timber straps that take laths, thereafter plaster would be applied.

Question 8

Can you explain timber framed construction to me?

Answer 8

• Outer leaf of brick or block with render typically.
• Stainless steel ties to fix brick or block (located @ studs)
• Breather membrane over sheathing (either ply or OSB)
• Sheathing
• Timber stud frame (depth varies)
• Vapour control layer
• Internal linings - usually plaster board either fixed to studs or on straps.

Question 9

What is a DPC?

Answer 9

Damp proof course, usually 150mm min above ground level.

Question 10

What are wall tie centres in a masonry wall?

Answer 10

450mm vertically and 900mm horizontal, with at least 50mm of bedding of tie at either end. Spacing changes around opening e.g. to within 300mm of openings and movement joints.

Question 11

What are wall tie centres in timber frame construction?

Answer 11

450mm vertically and 600mm horizontal. Spacing changes around openings e.g. to within 300mm of openings and movement joints.

Question 12

When specifying lime mortar what is the general ratio used?

Answer 12

1:3, 1 part lime to 3 parts sand for fine ashlar stonework however this can vary from building to building and type of stone used.

NOTE: Analysis of mortar can be carried out to ensure a good match.