With cost and sustainability being some of the key targets in the construction industry, it’s no surprise that timber frame construction is becoming increasingly popular. For some companies it’s the preferred method of build and it’s easy to see why when it’s cheaper to build with and faster to construct, due to the lower impact of weather conditions. Sound too good to be true? Well, there are some draw backs with this modern building method; in particular the risk of a fire during the construction phase. The impact of this for a timber frame construction site can be significant for both the site and the adjacent buildings.
Guidance has been produced by The UK Timber Frame Association (UKTFA) in relation to separation distances for timber frame construction, based on the height and width of the elevations. The aim is to ensure that the radiant heat emitted from a construction fire at the worst point during the construction is at an acceptable level, given the distance of the fire from the elevations of the adjacent buildings. The guidance adopts a conservative approach, in terms of radiant heat, wind effects and the fact that there are likely to be windows or combustible items within the adjacent facades. There are various levels of fire resistance in timber frame construction – Category A, B1, B2, B3, C1 and C2, with C2 being the most fire resistant, therefore enabling a reduction in separation distance.
Timber frame construction can still be used where adjacent buildings are very close. Our Fire Engineers can assess the site plan and the proposed compartment lines in the new building to recommend the use of different categories of timber frame in different compartments during construction. Our innovative approach maintains the maximum amount of Category A timber frame to reduce costs, whilst still mitigating the risk of external fire spread, should a fire occur during the construction period. The external fire spread of the proposed building can be assessed by using Computational Fluid Dynamics (CFD) modelling to quantify the exact radiation being received on adjacent building(s) and assessing its acceptability. This approach provides even more flexibility to use Category A timber in the timber structure.