Timber-frame party walls

Timber frame party walls are generally constructed of two independent wall frames positioned together; their function is to provide a protective barrier against the spread of sound and fire from one dwelling into the other.

The two party walls are to maintain a 220 mm minimum diameter and must always include a 40 mm min. cavity. It is important to note that no services are allowed to travel through the party wall cavity. As required by the building regulations, party walls require a minimum 1 hour fire rating. To achieve this in the timber frame, typically two or more layers of plasterboard are positioned between the two party walls to create the fire barrier. It is important that this fire barrier is not solely positioned between the wall but extended all the way up to roof level and that all cavity barriers and fire stops are correctly installed.

Conventional masonry walls and timber-frame construction

Conventional masonry walls can also be used as an alternative method for party wall construction in timber frame construction. Consideration must be taken at the design stage if this method is going to be used as it is the responsibility of the timber frame manufacturer to provide specifications and details of the wall construction and any alterations required to the timber frame.

Steps

Construction, weathering details, and cladding

Construction and weathering details should be provided for steps in the party wall by the timber frame manufacturer. The construction details must illustrate how the party walls will resist the spread of fire and weathering. Typically, the wall is protected against weathering by the cavity, breather membrane and the external cladding.

The external cladding can be:

Slates or tiles
A certified proprietary cladding system
Traditional timber cladding
Traditional render

Achieving weather and fire resistance

The timber frame manufacturer should provide construction and weathering details where steps in the party wall occur. The construction details must illustrate how resistance against weather and fire is to be achieved. A combination of an appropriate external cladding, ventilated cavity, breather membrane, and flashings at roof level generally provide the weather resistance.

Breather membrane should be lapped over the flashings. Roofing underlay should be carried up behind the flashings. Insect mesh should be used at the top and bottom of the cladding material and, where necessary, at openings to prevent insect infestation.

Party walls