boarding the loft

[valandian]

Hi,
I'm after a bit of advice regarding loft insulation.
unfortunately & stupidly I have started boarding the loft out without laying insulation down first. I even considered it at the time and decided against it for budget and labour reasons (I'm not much of a DIYer) which makes my decision even more stupid, I know.
I have now decided to pull the boards up and put the insulation down before I go any further with the boarding.
My joists are 150mmm deep and I'm thinking of using Space Blanket but which should I use for the best efficiency? 200mm thick and compress it or the 150mm thick?
The recommendation is 270mm but I really do not wish to packout the joists to give me the extra depth, is this another stupid decision?
Also the gaps between my joists range from 280mm to 410mm, the blanket having a width of 370mm, will the short fall be a problem?

If anyone can help me please do.

Thanks

 

[JohnD]

My joists are 150mm deep and I'm thinking of using Space Blanket but which should I use for the best efficiency? 200mm thick and compress it or the 150mm thick?
If you only have a 150mm space then there is no point in trying to fit in more than 150mm of insulation.

The recommendation is 270mm but I really do not wish to packout the joists to give me the extra depth, is this another stupid decision?
It is more work, but counterbattening will allow more insulation as well as making the floor more rigid and spreading the weight. I assume you are not making it into a habitable room or putting anything heavy up there, which will require reinforcement? Just storing the Xmas decs and your Judy Garland record collection?

Also the gaps between my joists range from 280mm to 410mm, the blanket having a width of 370mm, will the short fall be a problem?
Yes. You must cover the ceiling completely. You can cut the insulation to fit. Make it slightly wider than the gap so it squeezes in well without gaps. You can do this with big paperhangers scissors or a breadknife after unrolling, but it is quicker to cut the complete pack with a fine saw or very big knife like slicing a swiss roll.

 

[valandian]

Thanks,
Yes I am only going to be using it as storage but some things are more middle weight than light weight, I have a vast catolouge of Julie Garland LPs.
No seriusly though, I will be storing things like old prams, TV sets and such up there if it is safe to do so.

Back onto the insulation, my other idea was to insulate between or even over the rafters of the roof, this way I could put up a full 200 or so mm if I had some way of fixing it up there, maybe stapleing or nail gun.

Does this sound like a good plan ?

 

[JohnD]

You can do that if it is felted and in good condition (watertight, not too aged). You have to allow for good insulation of the roof timbers. Look at aluminised bubble-wrap type stuff to staple up. You will probably tear it if you are clumsy up there. The fibreglass above the first floor ceiling is I think your top priority.

Do some searches or browse the lofts section, there is lots of info already.

 

[valandian]

it is felted and there is absolutly no sign of damp up there!
Is there a risk of condensation? I was told there could be!
I saw the bubble wrap stuff today and, immediatly thought "that is the way to go!"
If this stuff can be as effective as the (rock wool/ space blanket) then I'm all for it, but I was told that it is better to do the floor!

Basicly I'm after effectivness verses cost!

And in the long run is it better to do the floor ?

Thanks for your help, I do appreciate it!

 

[masona]

it is felted and there is absolutly no sign of damp up there!
Is there a risk of condensation? I was told there could be!

If you do the ceiling insulation and roof rafters insulation together then the risks of condensation will be a problem, so it's one or the other and not both.

Use something like 3"x1" timber flat in opposite direction of the ceiling joists in line with the T&G boards joints for support as this will give you a cross air-flow and no need to cut out section for the pipe/cable of the ceiling joists which will weaken the joists.

 

[Reg_Prescott]

Hi,

Im in a similar position, I need to board my loft for storage, but my existing insulation is somewhat lacking. Anyhoo, I have stumbled on a product by "Knauf" called polyfoam supadeck. Is is basically loft boards with integral insulation. Good luck trying to get hold of it though, they only seem to sell to the trade They also do a product which is designed to go *over* loft boards. I have seen this in B&Q. I;m still checking it out, but it may be worth a look...

Good luck!