Replacing chipboard flooring and insulating Victorian property Another problem will be drying shrinkage of the new timber. If possible, have the new floorboards cut to length and screwed loosely in place, and leave them for a year to acclimatise (you can cover them with loose rugs as a temporary measure). Only then have the boards wedged tightly together and nailed with floor brads, before laying your permanent floor finish. Victorian insulation Q I own a semi-detached Victorian property with a two-storey rear extension that houses the ground-floor kitchen and first-floor bathroom. The extension is of single brick. I want to fit a new bathroom suite and as the room can get a bit chilly in the winter, with occasional condensation on the painted walls, I would ideally like to take this opportunity to have some form of internal insulation panels fitted. However, I am reluctant to do something that may cause different problems, such as damp building up between the insulation panels and brick wall. Can you offer any advice? LS, by email A I have answered this question several times before, but it keeps getting asked - especially at this time of the year. Victorian houses mostly have solid one-brick-thick (225mm, or 9in) walls. As long as these walls are kept warm and dry, they have a reasonably good insulation value. But if you adopt the common British practice of having the heating on for only two hours in the morning and six hours in the evening, then in between those times the walls get cold, condensation forms within the depth of the brickwork, and the insulation value falls to practically nothing. So my general advice to readers living in Victorian homes is to draught-proof the windows, and keep the heating running constantly at a low setting, as advised frequently in this column. Since you are planning a bathroom refurbishment anyway, however, this is a good opportunity to upgrade the walls. The thermal improvement will be directly proportional to the amount of internal space you are prepared to sacrifice to the insulation material. 50mm of rigid foam PIR board insulation (Kingspan or Celotex) would be great, but will reduce the internal space by that amount (plus another 12mm for the finish). In my own bathroom I have used just 25mm of PIR insulation and it has still made a big difference. Any competent builder or DIYer should be able to screw a simple framework of tanalised roofing battens to the external walls, with the PIR board fitted between the timbers. The important part is to then staple a continuous sheet of heavy-gauge polythene to the battens, with any joins lapped and taped. This vapour barrier is essential to stop warm, moist air from the bathroom finding its way through to the cold side of the insulation. Then finish by screwing cement board, such as Aquapanel or HardieBacker, to the timber battens. This can then be tiled or plastered according to your choice.