Loft insulation after the fact

[Jacko]

Our house is about 130 years old, we have a room in our roof space in which the angled ceiling is plasterboard fastened to the underside of the rafters (leaving about a 4" gap between the underside of the roof and the plasterboard.

The plasterboard is a recent replacement for lathe and plaster.

Although the room looks great we didn't put any insulation between the rafters and the plasterboard (worried about ventilation) meaning that we have a very large uninsulated roof area.

Is there anything I can do to insulate this space that doesn't involve removing the board and that wont compromise the ventilation between the rafters.

Thanks

Richard

[The Natural Philosopher]

Celotex is designed for this, but I doubt it will be easy to fit or effective, without removing the ceiling, no.

Bite the bullet?.

[meow2222]

Why would it be ineffective to attach it to the existing ceiling?

NT

[Ian Stirling]

Is the roof membrane breathable, or is it just tar paper?

Kingspan over the whole lot, and new plasterboard over the top of it.

I'd recommend biting the bullet. Get 25mm kingspan. Rip off the existing plasterboard. Place the 25mm kingspan along the rafters. Get some 75mm thick fibreglass, and some string or mesh.

Cut the fibreflass so that it fits between the rafters.

Fix the mesh onto the joists as you go up, holding the fiberflass up. Now, put vapour barrier plasterboard over this.

The easier way - if you have a reasonable budget is to use either rocksilk, or kingspan - which can simply be pressed into the rafters and then plasterboarder over.

[Stuart Noble]

I am battling with a similar situation where the original lath and plaster walls/celing are intact. On one side I have good access from the loft space so I hope to nudge 50mm celotex up between the rafters, leaving a 2" gap under the roof tiles. The other side is not so easy so I am resigned to taking some of the walls and ceiling down. As the man says, best to bite the bullet and put it down to experience :-)

[Jacko]

Thanks for the replies, I suspected this would be the case. The roof is original.

The area to be removed would be massive and I'm concerned about losing any ventilation so I might be tempted to take the advice of leaving the plasterboard as is and putting 50x50 battens up, insulation in between then more plasterboard over the top to give me a finish - any thoughts on this?

Cheers

Richard

[Stuart Noble]

Plenty of room for ventilation with 50mm celotex. I'd rather take the PB down and not lose the space

[The Natural Philosopher]

Oh..create a false ceiling inside? Still needs a whole new ceiling added..might as well take the oldone down..

[The Natural Philosopher]

If that is your choice, go for it. just seal the whole thing up completely before plasterboarding over.

[meow2222]

What I meant was just apply the insulation to the existing PB or L&P, and plaster over it.. No need to remove anything.

NT

[The Natural Philosopher]

Well its easier to board up and then skim..but I take the point. The issue is whether that is less hassle than taking down what is up there, and the loss of space..if these come out on the plus side, then of course its a good way to go. Here they wouldn't.

[Stuart Noble]

The OP has only recently put the pb up so it shouldn't be too dirty a job to take down again. Might even be able to re-use it if it was screwed.

[Ian Stirling]

Or if nailed.

I recently took down some plasterboard by simply finding all the nails with a magnet, then dremeling out a 1cm dia hole round all of them. Just pops right off then.

[Bill]

In message , Ian Stirling writes

What do you do when you are really bored?

[Ian Stirling]

:) Seriously though - it ended up at maybe 10 seconds/nail, which isn't so bad. Especially when you clear up by taking out whole sheets, rather than shoveling up lots of little shards.

[meow2222]

I'm mildly curious where you'd get a 1cm holesaw with 3.2mm shaft, or did you use a spiral saw bit or something else?

You're the sort of person that would probably be interested in papercrete, theres something on wiki about it.

NT

[Ian Stirling]

I used a carbide 'christmas tree' bit - which is perfectly happy with accidentally hitting the odd nail.

You don't need perfect circles, so it's quite fast. A proper holesaw would probably be faster.

[Weatherlawyer]

It sounds like you have plenty of room and are going to get the best of both worlds. Even if you hadn't lower down, the method would be fine nearer the apex.