The internals are now starting to transform the space from being a building site. The extension area at both the lower ground level and ground level is now being boarded out. The ceiling boarding is magnesium silicate by Multi-Pro. This is a moisture resistant board and has a greater breath-ability than plasterboard. The external walls will be plastered, but we have used 62.5mm Kingspan K17 insulated plasterboard on the internal walls (external prior to extension) that have been underpinned.
The floor insulation has also been laid. Again, we have used Kingspan K3 floorboard. This is 100mm thick, and achieves a U-value of 0.13 W/m².K. The insulation is laid directly onto the sub slab and covered with polythene ready for the screed. The screed arrived today on a mixer lorry. We are using a liquid flow screed, which allows a thinner layer (30mm) compared to traditional sand/cement screed (65mm). I’ve not used this type before, so will be interested to see how successful it is.
With the screed – why have you choosen not to put underfloor heating pipes in? This would definately be an integral part of my house upgrade. This is an ideal time to get rid of the radiators and a great selling point on the house too.
Thanks for the comment. This is about cost/benefit really. This lower ground floor area is so well insulated that we only have a heat demand of around 550 watts (0.55kW), equivalent to the amount of power needed to toast a single slice of bread. Therefore the investment required for underfloor heating compared to the amount of heat required (£ per kW) is not justified in this case. Heating to this floor will be provided by a length of finned copper pipe, which is to be set within the plinth of fixed items of furniture – doubtless I will do an entry on this when the time comes.