I have just ordered 'top-up' loft insulation because my existing insulation is just level with the joists.
My house was built mid 1970's and has a very shallow roof (impossible to stand up in the loft). The centre line of the loft is currently boarded over and we have the usual stuff up there - suitcases, boxes of stuff and christmas tree and decorations out of season.
Just wondering what to do when I put in the extra insulation. The current boarding is lying on top of the joists - but soon the joists will be 3 - 4" beneath the top-up insulation. Do people just lay the boarding on top of the new insulation? (Wont be much room in my loft once I've put the new stuff in!!).
I was told that if the boards went down on top of the extra thick insulation they'd push the insulation onto the ceiling and possibly crack it. So instead I left the joist level insulation in place and put Space Board on top and then boarded that. The alternative is to fix battens to the joists to raise the level sufficiently to clear the stuff.
I think I may well apply the top-up insulation at the sides of the loft and leave the existing boarded area with just the single level of insulation. Far simpler...
Yes - bit of a bugger really. I may just double-up the insulation down the sides of the loft and leave the centre area with the 'up to the joists' insulation with board over the top. The boarding itself will provide some additional insulation.
You might want to read the thread "condensation in roof space" before you start.
There's a number of options with the boarded area:
1) Do nothing, accept the higher heat loss. This may not be a problem if the areas small, and/or covered with boxes and other junk. You could use some foil wrapped insulation blanket to cover exposed floor area, moving it out the way when you're up there.
2) Put some additional circa 6-8" joists across the A frames to allow insulation to go under, refit the existing boards across the new joists. With typical roof construction you'll lose some width as well as height.
3a) Lay polystyrene insulation boards on top of the existing boards. Knauf Spaceboard extruded polystyrene is designed for exactly this job, and will accept light foot traffic without crushing, although you need a double thickness of boards and it is expensive - for a double thickness, if not on offer then it works out at about £13 a metre. In a loft currently with 100mm of insulation this probably means something like a ten+ year payback. You can lay Spaceboard directly onto the roofframes and then put the existing loft board over the top if you want a more durable surface, but it's more work.
3b) Same principle, but use construction grade expanded polystyrene (the stuff with a flame retardant coating, as flogged by Wickes or any builders merchant). Lay this on the existing boards, two layers of 50mm thick, and then put the cheapest protection board across the top of it - say 9mm OSB (oriented stranded board).
I used a mix of spaceboard and expanded polystyrene, laid over existing boards, with OSB on the top. The spaceboard was on BOGOF, and the expanded polystyrene kept the costs down further in the areas that I am unlikely to stand on (although it does support my weight with the OSB on top). There's nine inch screws to hold this sandwich in place, and because the loft floor is raised, I needed to refit the built in loft ladder.
As you may gather, this is a job that can become complicated and relatively costly. If it isn't a large area. the simplest way of doing it would be to just use Spaceboard on existing boards, and use No More Nails or similar to hold it in place.
Many thanks for that detailed explanation of my options Led.
I will probably take the opportunity to have a 'clear out' of the junk up there, and then the area that I will need for storage will be much reduced.
That being the case I will probably just leave that small area uncovered with the 'top-up' insulation and just rely on the original 'up to joist level' insulation, plus the existing boarding, plus the items stored, to provide the additional insulation of the remaining small area.
To make the job even easier all plasterboard used in ceilings has been manufactured to BSPB236 since 1954 and can support a weight of 22 stones. You will be safe to walk on it. Trust me on this one.
As a rider to that, I believe that since 1956, the stuff came with a fine mesh safety net built between the gypsum and paper layer that increases the loading that it can support to something like 30 stones to comply with the old by-laws that were floating around then - says me tongue-in cheek!
Methinks it must be Christmas and the time for some over-imbibed jollity.
From getting married in 1969 my wife and I lived in a series of 'provided' houses - Two different Navy married quarters, A Prison service house, and four different Police houses. In each of those properties I stored stuff up in the loft. We then bought a house, all of our own - and within two days of moving in, I went up into the loft, my foot slipped off a joist - and went straight through a bedroom ceiling! My wife was not impressed...
I know the feeling. One night I was in bed with the wife and we could hear a noise in the loft. I nipped up to investigate and a starling hit me in the face knocking my glasses off. I then slipped and my feet went through the ceiling. My fall was broken by the bedroom wall as one leg went into the bedroom and the other leg onto the landing.
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