I previously posted some images of my loft flooring project and the issues I found in the man jobs thread and thought I’d make this thread to keep it all together. So here we are!
The loft always had issues.
Issues 1 & 2 – When the previous owners floored the loft they only floored one third of it, right down the spine of the house. The floorboards were nailed straight to the joists compressing the insulation and causing a cold bridge from the 18mm flooring through the joists to the ceiling below. Not the most ideal thermal solution. Cleared the loft of everything but the spiders and measured things up.
I mentioned truss uplift earlier - I searched on seasonal cracks appearing and that’s what popped up more often than not. My surmising is that in the winter the joists to the left and to the right of the loft flooring are all cosey and warm around the 325mm of insulation but the centre of the joists are connected to a massive block of cold flooring. This disparity across the span of the joists causes them to contract in the centre and lift. We’re talking only a millimetre or two of uplift in my case but I’ve seen some examples of it being over 10mm!
This is an exaggerated interpretation of what I mean:
The solution is simple – remove the cold bridging and insulate the length of the joist spans to the same degree by removing the existing floor and laying more insulation down, making sure the new floor doesn’t compress the insulation. I’m going to lay 200mm insulation which matches that of the insulation to the right and left.
Issues 3 & 4 – A couple of things can be done for this. Firstly, is to make sure all the soffit vents are clear of insulation so that air can flow freely. Secondly is to make the new loft floor high enough so that air can flow under the floor and any cold bridging between the flooring and the ceiling is removed as best as it can be.
I looked at the options for raising the loft floor and decided on the system from LoftZone. The supports/legs are 279mm tall so with 200mm of insulation underneath these would give plenty of separation between the insulation and the flooring. I also decided on 22mm thick flooring rather than the 18mm fitted previously.
I just needed to work out how many uni-supports, tri-supports and crossbeams I’d need, not forgetting the floorboards. To the SketchUp!
I also used the SketchUp model for the best positioning of the LED battens which I increased from three to five. Light is good.
That looks like quite a lot of supports....
So I'd need:
Yuck.
The plan here is to reroute the fan ducting so that it's length is under and in the insulation and the fan is to be mounted on the gable end wall with a condensation trap fitted to vent it out a pipe in the wall. A bit like this:
Rather than go out through the roof the exhaust will use the pre-existing hole I made for it a while back. The pipe on the right of the image close to the floor is what I'll use to expel the condensate.
So that's the plan. I've done some already but still waiting on certain items, deliveries can take ages where I live.
The loft always had issues.
- Shortly after moving in a few years ago the ceiling below the loft started to show cracks at the taped joints of the plasterboard. There were tell-tale signs of a previous repair so I knew it would just happen again if I repaired them – the cause had to be found and fixed first.
- Similar to above, there were some cracks between the coving and ceiling in some rooms that would open in the winter and close in the summer. I filled these cracks previously with caulk but they just came back. This led me to think it may be caused by truss uplift.
- It never felt particularly dry in the loft either and this was made worse when the soffits were replaced as this sealed it up and insulation placed over the soffit restricted any airflow in and out of the loft. Any moisture was trapped.
- The flooring was uneven and seemed “soft” between the joists and creaked when I walked over it, suggesting the floorboards were compromised and had some movement in general.
- I discovered that whoever installed the extractor fan for the ensuite thought that it was acceptable to just vent in to the insulation! Really?!
- To fix the ensuite extractor fan issue I installed a new fan and ducting to the outside but the fan always leaked condensate despite the ducting being insulated. I need a permanent solution.
Issues 1 & 2 – When the previous owners floored the loft they only floored one third of it, right down the spine of the house. The floorboards were nailed straight to the joists compressing the insulation and causing a cold bridge from the 18mm flooring through the joists to the ceiling below. Not the most ideal thermal solution. Cleared the loft of everything but the spiders and measured things up.
I mentioned truss uplift earlier - I searched on seasonal cracks appearing and that’s what popped up more often than not. My surmising is that in the winter the joists to the left and to the right of the loft flooring are all cosey and warm around the 325mm of insulation but the centre of the joists are connected to a massive block of cold flooring. This disparity across the span of the joists causes them to contract in the centre and lift. We’re talking only a millimetre or two of uplift in my case but I’ve seen some examples of it being over 10mm!
This is an exaggerated interpretation of what I mean:
The solution is simple – remove the cold bridging and insulate the length of the joist spans to the same degree by removing the existing floor and laying more insulation down, making sure the new floor doesn’t compress the insulation. I’m going to lay 200mm insulation which matches that of the insulation to the right and left.
Issues 3 & 4 – A couple of things can be done for this. Firstly, is to make sure all the soffit vents are clear of insulation so that air can flow freely. Secondly is to make the new loft floor high enough so that air can flow under the floor and any cold bridging between the flooring and the ceiling is removed as best as it can be.
I looked at the options for raising the loft floor and decided on the system from LoftZone. The supports/legs are 279mm tall so with 200mm of insulation underneath these would give plenty of separation between the insulation and the flooring. I also decided on 22mm thick flooring rather than the 18mm fitted previously.
I just needed to work out how many uni-supports, tri-supports and crossbeams I’d need, not forgetting the floorboards. To the SketchUp!
I also used the SketchUp model for the best positioning of the LED battens which I increased from three to five. Light is good.
That looks like quite a lot of supports....
So I'd need:
- 70x Uni-supports
- 40x Tri-supports
- 35x Crossbeams (1.8m long)
- 21x floorboards (2.4m x 600mm x 22mm)
- And a lot of screws. Not nails. Definitely not nails. Nope.
Yuck.
The plan here is to reroute the fan ducting so that it's length is under and in the insulation and the fan is to be mounted on the gable end wall with a condensation trap fitted to vent it out a pipe in the wall. A bit like this:
Rather than go out through the roof the exhaust will use the pre-existing hole I made for it a while back. The pipe on the right of the image close to the floor is what I'll use to expel the condensate.
So that's the plan. I've done some already but still waiting on certain items, deliveries can take ages where I live.
.