Insulation Board

[Anonymous]

The house we are buying has insulation board as ceiling - they never got around to putting the plaster board on obviously - and then a gap between that and the roof. Will the insulation board as it is or would we need to insulate between it and the roof further, or would just putting up a proper ceiling do the insulation job?

Thanks

 

[Anonymous]

Can you be mores specific about this insulation board? What type is it, and how thick? How is it fixed - between the joists or against the bottom face of the joists as a continuous sheet?
The recommended thickness for mineral wool or fibreglass loft insulation is 250mm (10in). Do you think your insulation board is likely to have an equivalent u-value to this?

 

[Anonymous]

umm, err, ahh.... well, I think its made up of individual panels which are defintely fixed with batons which I think are attached to the joists. As for the thickness, really couldn't say without having another look but I doubt they are as much as 10in - that seems awfully thick.

The survey refers to them as polystyrene panels, but they definitely aren't that.

Sorry, I'm not being very helpful - all I know is that the vendors disputed the surveyor calling them polystyrene tiles when I went round to discuss some of the aspects and insisted that it was insulation board which had never been covered by a plasterboard ceiling.

Hx

 

[Anonymous]

It may be a Kingspan product called Kooltherm and is an insulated drylining board, it is on their website and you can have a look at it.

I have read good things about it if used in the correct way ie not hiding away problems for 3 years and not using it in certain buildings when traditional methods would be more suitable.

I think people use it to insulate single skin brick walls in old extensions by either fixing it to battens or plaster dot and dab fixing

 

[Anonymous]

Our attic ceilings were clad with some strange board - rather a coarse texture, like those cheap pinbords. Done for cheapness rather than insulation, I think.

 

[Anonymous]

Moo - that sounds exactly like the ceilings on the top floor of the property - oh rats! and I thought I was going to get away with just plasterboarding over them.......

Hx

 

[Anonymous]

Is this the same as the "fibreboard" ceilings I have I wonder.
My surveyor when I bought recommended replacing this with plasterboard etc. (Does everyone's list of things to do seem to get longer and longer?)

 

[Anonymous]

Helena - if the ceiling is actually fibreboard, like Moo's, then it's not going to give you any real insulation. It's also not a very durable material.
If this is the case, then if I were you, I would start again (sorry!). Rip off the fibreboard and fix a new plasterboard ceiling. How you insulate this depends on whether you can get access to the roof space above it. Is it like a normal attic or loft, with an access hatch? if so, then you can just get some rolls of fibreglass, take them up there and unroll them.
If you can't get above the ceiling, then you'll have to devise a method of getting the insulation in place before you board the ceiling. I've seen this done by laying it across the joists (instead of between), so that it hangs across the gaps. I've also seen it done by placing the insulation between the joists, supported by lots of strands of string until the boarding is in place. You could also do it with rigid insulation batts wedged between the joists (probably the more expensive option).
One final note: the above suggestions assume that (a) your house is not listed, and (b) that the ceilings are not in any way special. If either of those situations apply, then of course you should proceed appropriately with (a) LBC and/or (b) the appropriate ceiling materials.

 

[Anonymous]

>>Is it like a normal attic or loft, with an access hatch? if so, then you can just get some rolls of fibreglass, take them up there and unroll them.

Sounds easy - so long as the access hatch is big enough and the gap between the rafters wide enough - I had to unroll mine and poke it up, then climb up, roll it back up, carry it to the right spot and unroll again. It was taking ages as I could only do a couple of rolls before I was knackered and itchy!
Then my son and I (he was 7) devised a method whereby I removed the landing skylight (excavation in the roof showed it not to be fastened down as thought but fixed by muck) and I lowered a washing line with a loop in it down the 16ft to the landing - he good little kid, put this loop round a wrapped roll and I hauled it up. It still wouldn't go through the rafters to the main bit of the roof but the awkwardness was reduced considerably. And son enjoyed it - especially when he was allowed in the roof to do the last rolls. Took a day.

 

[Anonymous]

I bet that was hot work! So your loft insulation actually warmed you twice - once installing it, and now by keeping the house warm.

What a bargain!

 

[Anonymous]

The good news (based on Hazel's tale) there is no loft in this property. As far as I know the insulation board has nothing between it and the roof tiles (maybe that should be the bad news!).

Additional good news is that the property isn't listed in anyway and we can do what we like (within budget reason) with the ceiling.

So, any cheap options?

Thanks

Hx

 

[Anonymous]

I'm still unclear about the structure that we're talking about. Is this a flat roof with a ceiling a few inches below it? Or is it a pitched roof with a flat ceiling below it (thus creating a pyramid shaped void). Or is it a pitched roof with a pitched (sometimes called vaulted) ceiling fixed to the underside of the rafters?

I know this is a lot of questions, but the answers do affect what you can do.

 

[Anonymous]

David

Don't worry about the questions, I'm probably not making myself very clear. The roof is pitched and the ceiling runs at the same angle as the pitch so I guess that must make it vaulted.

I have had a quote for £5000 which involves removing the insulation board, putting ventilation vents in the roof, adding a vapour barrier to protect the soffits and then putting up a plasterboard with a fibre insulation backing (oh and then skimming of course).

Unfortunately, as this isn't the only work needed doing on the house, I can't afford this - do I need ventilation & vapour barrier??

Thanks

Helenax

 

[Anonymous]

OK, Helena - I can visualise it now.
Ventilation - a big "yes". You must ensure that the timber structure of the roof is well ventilated, to protect against the possibility of condensation and the damage this might do to the timbers.
"A vapour barrier to protect the soffits"? Well, I confess that this phrase has me a bit puzzled - but I'm not in any way a professional. A sarking membrane (ie: roofing felt or one of the more modern breathing equivalents) under the tiles is always desirable, as a second line of defence against the possibility of rain or snow blowing in under the tiles. But it must be said that thousands of old properties don't have this, and still manage to keep the rain out perfectly well.
But I'm not sure why the soffits need protecting with a vapour barrier - perhaps one of the expert roofers will kindly contribute to this thread.

 

[Anonymous]

Thanks David - it has already got roofing felt - so we've at least not got to worry about that one!

It will be interesting to get an opinion on the options from a roofer.

Helenax

 

[Anonymous]

I believe that board is tentest board
was used for expansion joints, partitions etc
Sometimes (when i can get hold of some) I use it to start the wood burner.

 

[Anonymous]

Ask the roofers how or where on the roof he is going to install the ventilation
My guess would be vent holes in the soffits and to the top, 'ridge vents'.
As to the plasterboard, if the roof structure is strong enough, cross batten and fix foilback plasterboard, and use that thin double foiled insulation behind it. (i forgot the name of it)
If your rafters are deep enough that should give you plenty of air space
How deep are the rafters?

 

[Anonymous]

Hi Jake

Thanks for the advice. I don't think there's a great deal of space between the current ceiling and the roof - the wall space (or what they are using as a loft ) is only a three or so feet wide, so I suspect the roof space isn't much bigger.

The thin foil insulation sounds interesting. Would I be able to use this without having to put in ventilation?

Hx

 

[Anonymous]

Have a look at the 'lapvent' website, just google the name and scroll through the headed pages on the left. There could be something there that may help, or at least give you an idea or two.