Vapour Barrier Suspended Timber Floor Construction Detail

Some people and organisations will refer to the material that controls vapour movement as a vcl and some will call it a vapour barrier.

Vapour barrier suspended timber floor construction detail.

Moisture management for suspended timber floor construction many suspended timber floor constructions have discontinuous insulation between the joists. That leaves an opening to improve moisture management and airtightness by fitting a tyvek membrane and carefully sealing the gaps and joints. At the turn of the 18th century when construction techniques moved from boarded floors installed directly on the ground to suspended timber floors over a ventilated chamber the innovation solved a significant problem. Vcls or vapour barriers will only reduce the vapour movement to an acceptable level.

Previously floor timbers had been prone to damp and rot thanks to their direct contact with the moist ground. To answer your question introducing a vapour barrier to the underside of the floor joists would be a complete waste of time that is other than to assist in the air tightness of the building which is another bone of contention whereas introducing a vapour barrier over the top of the floor joists may well provide some long term benefits by reducing the amount of water vapour introduced to the. Suspended timber floors required under clause h1 energy efficiency. A damp proof membrane or dpm is a waterproof barrier that s introduced between your sub floor and your wood floor.

Hi i did just like to check my plan for installing some insulation in a timber joisted suspended wooden floor in a 1900 ish terraced house. My plan is to remove the floor boards using some scaffolding netting stapled between the joists up and over up and over to hold some fibreglass insulation clean out any excess rubble and double check the air bricks. The ground should have a layer of concrete poured across and there should be a ventilated gap of at least 150mm between the underside of the timbers and the concrete to prevent moisture gathering and affecting the condition of the joists. Once the wedges are removed they are replaced with strips of cork or polyethylene foam to act as a compressible filler and to help prevent cold bridging.

It is important to remember that no material is completely vapour proof so the term barrier can be slightly misleading. Effectively a thick plastic sheet a damp proof membrane dpm is used to create a barrier between a concrete or screed subfloor and a wood floor. A vapour control layer with a low sd value that allows limited vapour transmission especially recommended on mineral wool wood fibre cellulose fibre and other breathable insulation materials. Suspended timber floor as a requirement of the building regulations the structure should be protected against the growth of weeds and other plant life.