Performance of timber frame
As for any other form of construction, timber framed buildings must comply with the requirements of UK Building Regulations. The structure for all timber frame houses must be designed by a qualified structural engineer or be approved by an organisation such as TRADA Technology to verify the structural stability of the construction.
Timber frame houses, flats and maisonettes have for many years been built to a maximum height of three storeys. However, following changes to the Building Regulations, four storeys or more is no longer unusual and flats are now being constructed up to six or seven storeys high. Timber frame is being used extensively for hotels, hostels and nursing homes.
Timber which remains dry (ie at a moisture content of 20% or lower) is not at risk from decay. Properly designed and constructed timber frame buildings do not rely on preservative treatments for durability. The wall and its framework are designed so that the timber will maintain an equilibrium moisture content comfortably lower than that which could allow fungal growth. It is, however, common practice to treat structural components in the external wall and ground floor as insurance.
The ease of incorporating insulation into the timber frame superstructure means that the requirements of the building regulations can easily be met and much higher levels can be achieved.
Fire is an emotive subject and is one of the first issues raised when timber frame construction is discussed. However, timber frame buildings must meet the same fire regulations as all other types of construction and therefore pose no greater risk to their inhabitants.
Timber stud partitions and timber joist floors have been used for many years as fire separating elements and their performance has been proven time and time again in test and real fire situations. In the unlikely event of a fire starting within the construction, firestops and cavity barriers prevent fire spread through concealed areas. Full scale fire tests undertaken on a six storey 'Timber Frame 2000' demonstration building showed compartmentation and building integrity maintained throughout the test. TRADA and BRE fire safety research concluded that “Timber frame performs as well as other construction in fire and life safety is at no greater risk”
Timber frame structures rely to a large degree upon structural separation to achieve sound reduction, rather than simply incorporating more mass into a structure. Tests on timber frame party walls comprising two separate stud walls showed that sound insulation performance was well above the levels required in current Building Regulations. Sound resistance requirements in timber party floors are currently met by separating the floor deck from the walking surface by floating layers, incorporating insulation and having sufficient mass in the deck and ceiling. Higher levels of sound insulation can be achieved by de-coupling the ceiling from the joists by the use of resilient bars to to support the ceiling or by installing separate ceiling joists.
TRADA Publications available from the Bookshop
Timber Frame Construction. A 256 page TRADA book giving detailed guidance on timber frame construction. 3rd edition, published 2001.
Introduction to timber frame construction. WIS 0 - 3.
Timber frame housing – materials specification. WIS 0 - 5.
Timber frame construction – site control. WIS 0 – 8.
Surveys of timber frame houses. WIS 0 – 10.
Breather membranes for timber frame walls. WIS 1 – 35.
