Loft insulation for 12" spaced ceiling joists?

Hi

The ceiling joists in our 1930's house are spaced at 12" (300mm). The loft insulation rolls that I have seen in B&Q and Wickes are 1160mm wide. Should I buy these and cut them down to 300mm, or are 300mm rolls available elsewhere?

I am aware that one should not lay the insulation right into the eaves. However, my loft is quite drafty (the roof felt is damaged in places). Also the ceilings extend into the roofspace. I am not sure how to describe this, but I guess readers will understand if I say that the walls slope at about

45 degrees to meet the ceiling. How best can I insulate this arrangement?

Thanks for reading this,

David

Reply to
Aldrich
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In message , Aldrich writes

Buy the rolls that are about four feet wide, then cut to size, with an ordinary hand saw, *before* unwrapping the rolls.

I was sceptical, but it works brilliantly :-)

Reply to
Graeme Eldred

The stuff I used a few years ago was perforated at a variety of widths and just ripped. I don't remember wether 12" was an option. Marketed as 'Pink something', and even used a panther as a logo!

Reply to
Andrew Chesters

A hand saw? Doesn't it get chewed up on the teeth? I always use a long, sharp carving knife myself (again, before unwrapping!).

David

Reply to
Lobster

Something like a jack saw works fine I found...

Reply to
John Rumm

They are pre-cut almost all the way through at 1/3, 1/2 and 2/3 so you can just rip them off at the size you need.

Reply to
Mike

I was able to get mineral wool from Wickes last year that fitted my joists exactly, IIRC they are 12" apart. As for your ceilings, I can imagine two options. Either you insulate the 45 degree bits on the inside of the room by adding plasterboard over battens & insulation, or you stuff insulation down your eaves, but leave the occasional gap so that air can circulate in your loft freely - I can't imagine you need to keep the entire length of the eaves free to get adequate circulation.

Andy.

Reply to
andrewpreece

That is wrong and would cause damp and then rot in the sloping ceiling rafters. The correct way is to remove the plasterboard and insulate with something like celotex between the rafters and below the rafters leaving 50mm gap on the cold side of the insulation. Also making sure there is good ventilation in the eaves and if not add some soffit vents or somehting. There must be a vapour seal on the warm side of the insulation which can be acheived with foil backed plasterboard or taping the insulation.

If the sloping bits are only short in length and the above isnt worth the effort I'd just put insulated plasterboard on the inside attatching with nails or screws.

Basil

Reply to
basil

The sloping bits are only about 300mm long. I really don't want to replace the plasterboard - I have limited diy skills! So if I leave the existing plasterboard / lathe and plaster there, are you suggesting that I add extra plasterboard to the cold (loft) side?

I had wondered about putting polystyrene on the cold side, but still leave some gap to the eaves. Any thoughts?

Thanks again

David

Reply to
Aldrich

I have much the same position. I was thinking of pouring some of the particulate insulating material that I have seen down the sloping part of my attic. I wonder what people think of that?

Reply to
Timothy Murphy

I've got the same problem as well - you should see my gas bills :-(

No, if you bung loose-fill stuff down there it will do a great job of completely blocking the space, stopping all ventilation coming up there, and bring about dry rot.

(That's if the stuff doesn't all fall out of the gaps at the bottom first!)

David

Reply to
Lobster

A hand saw indeed - yes, I thought it would clog the saw teeth, but it doesn't. Probably because the stuff is so tightly packed, whilst still rolled. Works perfectly.

Reply to
Graeme Eldred

No, only if you wanted to insulate from the inside, but that would mess up your decorations or need plastering etc

That is your best bet! Try to leave 50 mm gap on the cold side of the insulation. There should be no gap atall on the warm side ie it should be pushed firmly against the plasterboard otherwise its a waste of time. You could try pushing the insulation in place then pushing in lengths of timber along the sides of the rafters (say 2 x1's) and then screw/nail them to the rafters so assuring the gap above the insulation and holding the isulation onto the plasterboard below it.

Do you have foil on the back of the ceilings plasterboard? If not you could paint a few coats of oil based paint on the ceiling from inside the room for a vapour seal. And if you want to increase the ventalation in the eaves some time in the future that would be a good thing.

Celotex/kingspan gives beter insulation than polystyrene for any given thickness plus its easier to squeeze into betwwen rafters without snapping. Its a bit more expensive though. You get if from an Encon if theres one near you or a buliders merchant will order it for you.

cheers Basil

Reply to
basil

Useful info on this here (and elsewhere on the same website:)

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Reply to
Lobster

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