Floors consisting of pre-cast concrete units, including concrete plank or beam and block, can be rapidly installed and are suitable for use where conditions preclude a groundbearing floor. Insulation should be installed above the bearing surface.
This construction is compatible with masonry and timber framed wall constructions and may be used with underfloor heating set in a screed.
The properties of Ballytherm Insulation match those required for this application: it is robust and moisture resistant, whilst its low thermal conductivity minimises the thickness of insulation within the floor construction.
The thickness of Ballytherm Insulation required to meet regulations may be determined from table 6.
Design guidance
A suspended floor does not require a DPM. Where a Radon barrier is required it may be installed across the top of the structural floor beneath the insulation, or may be installed within the concrete covering of the sub-floor void. In all cases the radon barrier must extended across the entire footprint of the building. Joints in the surface of the structural floor should be grouted and a 13mm levelling screed laid (maximum permissible deflection +/- 5mm over 3m length).
Where the Ballytherm boards will be overlaid with a screed, a VCL/slip sheet of 1000 gauge polyethylene should be laid between the insulation and the screed to prevent condensation at the interface and possible screed migration. The screed should be at least 65mm thick and may incorporate pipework for underfloor heating. Edge insulation should be installed around the perimeter. The depth of the edge insulation boards should be equal to the combined thickness of the insulation and screed.
Where chipboard or other sheet flooring is to be laid onto the Ballytherm boards without a screed, a VCL/slip sheet should be installed between the insulation and the flooring. The VCL/slip sheet will allow for differential movement and protect the flooring from construction moisture particularly during the drying out period. The VCL should be turned up behind the skirting.
At thresholds and other places where heavy traffic or high loadings are expected (for example beneath kitchen or sanitary fittings) timber battens should be installed to prevent the flooring sagging (figure 11).
Sitework Installation sequence - beneath screed
Grout slab and lay levelling screed.
Fit vertical edge insulation.
Lay Ballytherm boards across the surface of the floor in broken bond.
Lay VCL/slip sheet over the boards with joints lapped and sealed.
Pour screed.
Installation sequence - beneath sheet flooring
Grout slab and lay levelling screed.
Fit timber battens at thresholds and points of high loading.
Lay Ballytherm boards across the surface of the floor in broken bond.
Lay VCL/slip sheet over the boards with joints lapped and sealed.
Lay sheet flooring
Points to watch
Ensure boards fit tightly together.
Seal service penetrations with sealant.
Test any services before pouring the screed.
Protect Ballytherm boards from traffic while laying screed or flooring.
Protect exposed board edges when levelling the screed.
