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

In message , Aldrich
writes

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?

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 :-)
--
Graeme, Scotland

Aldrich wrote:
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



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!

Graeme Eldred wrote:
In message , Aldrich
writes


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?


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

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

Lobster wrote:


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


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

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

--
Cheers,

John.

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"Aldrich" wrote in message
...
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?


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.

"Aldrich" wrote in message
...
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



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.

On Mon, 21 Feb 2005 00:35:03 -0000, "andrewpreece"
wrote:

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.


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

Thanks very much to all who replied to my question.

Basil, thanks for your advice. You wrote:

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.

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

Aldrich wrote:


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?

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?

--
Timothy Murphy
e-mail (80k only): tim /at/ birdsnest.maths.tcd.ie
tel: +353-86-2336090, +353-1-2842366
s-mail: School of Mathematics, Trinity College, Dublin 2, Ireland

Timothy Murphy wrote:
Aldrich wrote:

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?

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?

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

In message , Lobster
writes
Graeme Eldred wrote:
Buy the rolls that are about four feet wide, then cut to size, with
an ordinary hand saw, *before* unwrapping the rolls.

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

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.
--
Graeme

On Mon, 21 Feb 2005 23:39:55 -0000, "Aldrich"
wrote:

Thanks very much to all who replied to my question.


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?

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

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

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

Aldrich wrote:
Thanks very much to all who replied to my question.

Basil, thanks for your advice. You wrote:

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.

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?

Useful info on this here (and elsewhere on the same website:)
http://www.secondsandco.co.uk/Pages/...th-rafter.html

David