1. Learning Outcome Lesson Objective
Understand the techniques used in the construction of superstructures for low-rise domestic and commercial buildings
Lesson Objective
To be able to explain the techniques used for construction of external walls in domestic timber frame construction

2. Wall construction Knowledge check?
Where in modern houses are dense blocks used?
How can cavity walls be insulated?
What is a cold bridge?
How can cavities be closed at the jambs and how is damp penetration avoided?

3. Timber framed construction
The timber frame building offers several potential advantages over more traditional forms of building:
What are they?
Fast construction
Good quality control
On site construction is reduced because of prefabrication
Less dependence on traditional ‘wet’ skills
Reduced dead-load.
Good thermal insulation

4. Timber framed construction

5. Timber framed construction
With timber frame construction external and internal load bearing walls are formed out of timber frames that have vertical timber studs nailed to top and bottom timber plates.
The studding will be covered on the outside by a sheet material called sheathing, which will usually be plywood.
What is the purpose of this sheathing?
To stiffen the frame and to help prevent
deformation from wind loads.

6. Timber framed construction
The studding will be covered on the inside by plasterboard to provide an acceptable finish.
Weather protection can be provided by external timber cladding or tiling or more commonly in this country by an outer leaf of brick work.
The frames are usually pre-fabricated in storey high panels not more than 3.6 metres in height allowing easier handling on site.
Larger panels would need the use of a crane on site.

7. Timber framed construction
Breather membrane
A waterproof, but vapour permeable, layer protects the timber from any water, such as wind driven rain, which finds its way across the cavity, whilst also allowing any moisture vapour in the panels to escape.

8. Timber framed construction
Vapour Control Layer
To prevent condensation occurring within the external wall panels some form of vapour control layer is required in between the insulation and the plasterboard.
The most common material is polythene sheet

9. Timber framed construction
Cladding
In the UK, brick is by far the most common type of cladding to timber framed houses.
Unlike a traditional brick and block house the brickwork can be built (and usually is) after the roof has been completed.

10. Timber framed construction
Cladding
Brickwork, however, is not necessarily the most practical cladding - for three main reasons.
What are they?
its weight means it cannot be supported by the timber frame and therefore requires a foundation
a free standing wall would soon buckle and bulge in high winds so it must be restrained by the timber frame
the method of restraint (wall ties) must allow for differential movement between the brickwork and timber.

11. Timber framed construction
Brick Cladding

12. Timber framed construction
Wall ties
Wall ties must be fixed to the studs and not just the sheathing.
The flexible wall ties should be laid to a slight gradient (i.e. sloping outwards) to ensure that shrinkage in the frame does not create a back fall in the ties when the frame shrinks.

13. Timber framed construction
Fire and Acoustic Protection
If the house is semi-detached, the separating walls must provide fire protection and adequate resistance to airborne sound.

14. Timber framed construction
Openings
The panels are
'trimmed' to form openings

15. Timber framed construction
A lightweight lintel normally requires a timber cavity barrier.
The need for a separate cavity tray again depends on location and lintel finish (galvanised, stainless steel, special coatings etc).
Most lintels for timber framing require lintel restraint clips which must be screwed or nailed to the timber frame. These help restrain the lintel but must, at the same time, allow for differential movement between the timber structure and the brick facing.  

16. Steel frame housing
The principles of modern steel frame construction are similar to timber frame construction.
Use is made of a platform frame but the panels are made of galvanized steel sections rather than timber.
In the factory the sections are welded or riveted together but on site self tapping screws or bolts would be used.

17. Steel frame housing
The positioning of the required insulation in the external wall is slightly different for steel frame construction compared to timber frame construction.
Rather than being positioned between the frame members, foil backed insulation boards are fixed to the outside face of the frame members, keeping them warm so that there is usually no need for a vapour check.