A Quick Guide to Building a Timber-Frame Home

23 May 2020 Paul Newman, Self Build Director
Kingspan TEK roof panels - Copy

We believe passionately that timber frame is the best solution for most new homes. They’re warm, draught free, and have low running costs. Precise engineering quality means more and more self builders are choosing to build their new home with timber frame. Read on to find out all about the ins and outs of building with a timber frame. For more information, visit our website: https://www.potton.co.uk/self-build-resources

Build the footings and floor structure

Foundation substructure
In most cases, your groundworker will use a traditional strip foundation approach. This involves digging trenches to the depth and width required by the foundation design and then filling them with poured, ready-mixed concrete.

An initial 2-3 courses of blockwork are laid, with openings for service entries or exits created by pre-cast concrete lintels. Then the ground floor structure is installed – typically a beam and block floor where pre-cast concrete beams are used to span between load-bearing walls. The gaps in between the beams are filled in with concrete blocks laid flat.

In some systems the concrete beams are replaced with insulating polystyrene elements. In both cases a damp-proof membrane is incorporated into the floor and then insulation and finally a screed layer introduced – a thin ‘slip’ membrane separates the insulation from the screed. The insulation and screed are not normally completed until after the building structure is erected and, in most cases, with our customers the screed incorporates the underfloor heating pipes.
 

Building the walls...

The substructure and ground floor works are completed with a ‘kicker-brick’ course of blocks on top of the beam and block floor – these form a square and level surface on which the first part of the timber frame, the sole plates, are fixed. It’s critical that the sole plate is level and square as it sets out the rest of the building. The ground-floor external wall panels are delivered as prefabricated elements, complete with insulation and all membranes from the factory. We normally erect the structure using a crane to lift, position and manoeuvre each panel into place.

More information on ULTIMA, our most popular external wall system, is available here https://www.potton.co.uk/what-we-do/build-systems/kingspan-ultima. ULTIMA provides low U-values, with excellent airtightness performance. The inner lining of Kingspan Kooltherm significantly reduces thermal bridging. Kingspan ULTIMA is an advanced timber frame system with sector-leading performance characteristics.
 

...and the floors...

The first-floor joists are fitted onto the tops of the wall panels – these are hung off the external walls using metal hangers. For the first-floor deck we use chipboard with a permanent weather-proof coating on both sides, which is then glued and nailed into position on top of the joists. This process is repeated for additional storeys, with the roof structure sitting on top of the wall plates on the external walls. We always use metal open-web joists for the structure of the floor. The metal webs massively simplify the positioning of services compared to solid timber or I-joists and also enable wider spans to be constructed before needing additional beams.
 

...and finally the roof structure!

Trussed rafter roof
We use a variety of roof structures and their selection depends upon detailed design and specification considerations, in particular whether the roof space is being used as living space or not. Roof structures are either trussed rafters, attic trusses, panelised roof systems (eg. Kingspan TEK structural insulated panels) or cut roofs where the structure is mostly fabricated in-situ by a skilled carpenter.
 

Getting weathertight

The whole timber frame is wrapped in a breather membrane that stops water entering but allows moisture to escape. Depending on the rigour of the approach to airtightness, the joints between the panels and window openings may be sealed with specialist tapes and seals.
 
Once the structure is up then the roof should be ‘felt, battened and tiled’ as quickly as possible. Next come the windows and doors – at this point the structure is effectively weathertight. The external cladding is taken off what’s known as the critical path and work can carry on inside and outside the building at the same time as the brickwork or other cladding is being fitted externally.
 
A key advantage of timber frame is the ability to get weathertight quickly on site and then progress trades internally and externally independently of each other.
 

First fix

With the house weathertight, internal works can commence. First off is first-fix carpentry works which in a way is preparation for plasterboarding, electrical, plumbing, heating and ventilation works. Once the first-fix carpentry work is completed then other trades can follow on, so the property is ready for plasterboard dry-lining. We recommend the use of tapered edge taped and jointed plasterboard but many customers prefer to skim. In practice, the different is minimal as long as the team applying the skim coat are tidy in their work.

Finishes

The glamourous bit – not to be rushed. The construction process ends with second-fix electrics, plumbing and carpentry, where all the surface elements of the house are installed – from kitchen units to light and power sockets and fittings, bathrooms, taps and staircases. The house is then ready for tiling and the fitting of flooring finishes, and then finally decoration.