Tuesday, 19 June 2012
Part of the first floor over the utility room (with the heat pump) we wanted to fully fill with insulation to give as much soundproofing as possible. The plan was to 'inject' them with warmcel insulation from below (just to be confusing the photo is taken from above!). When we fitted the ceiling boards on the GF ceiling we let off a strip 400mm wide roughly in the centre of the floor, through which a pipe could be inserted into the floor and the insulation blown in. We were told to tape up all gaps, even those only 10mm wide, so I assumed the insulation could be blown with some force. I am not sure this was a correct assumption! The pipe can not really spray any distance and needs to be able to get right to the ends of the joists, which gets increasingly difficult the further you get from the insertion hole. The pipe is flexible and so negotiating it around things like the floor struts is not easy when you get a couple of meters away from the hole! To ensure you reach the end of each joist I think you need to be quite methodical and measure how far in the hose has gone to ensure the insulation has gone right to the end. We ended up taking up the ply on top of the joists to ensure the insulation had gone right to the end. I had thought the beauty of this method of insulation was that you didn't need to take up all the first floor again but I am now not sure it is reliable enough just to trust all joists are fully insulated to the end without checking.
When it came to filling the last section of the floor, where the pipe had been inserted, either mesh can be put over the gap, a hole made in it and the last bit filled (similar to the wall insulation). Or the last bit of ceiling board can be fitted, a small hole cut into it in every joist bay though which the last bit is filled.
We went for the latter as using the mesh was more difficult as one side of the ceiling was hard up against a studwall and so there wasn't a lot to staple the mesh to.
The cut out holes are kept. A small batten is inserted into the hole and screwed to the ceiling board either side and the hole can then be fixed to the batten.
The holes re-fixed.