Insulating Ceiling - should I rip out what is already there

[Charlie]

I've got a downstairs bedroom at the rear of the flat that I really struggle to heat up. I replaced the tiddly radiator but I still have trouble heating it up tin the winter.

It's got two external walls but I think the culprit is the flat roof. I was thinking of pulling down the ceiling and putting up some Kingspan and reboarding.

However I had a quick look to see what the ceiling construction was and to work out what the depth was and I'm unsure of the construction.

It looks like plasterBOARD and lathe. Here's a picture:

this going to be really messy to rip down? Why are there all these lathes/batons between the joists and the plasterboard?

[Andrew Gabriel]

to heat up. I replaced the tiddly radiator but I still have trouble heating it up tin the winter.

thinking of pulling down the ceiling and putting up some Kingspan and reboarding.

Same advice I gave in another thread - use an infra-red thermometer to see which surfaces are the coldest, and hence losing most heat.

work out what the depth was and I'm unsure of the construction.

lathes/batons between the joists and the plasterboard?

Is the building old enough for it to have been lath and plaster originally? The laths are going the wrong way if that joist is representative of all the others.

Difficult to tell from photo, but it looks like plasterboard now.

If there's no insulation in there, that is quite likely a very significant heat leakage.

[Tim Watts]

Gawd knows - unless it was plaster, they knocked the plaster off and could not be bothered to remove the laths?

Can you lose 2.5" of height? If so, 50mm celotex (etc) over that without removing anything, then new plasterboard.

That will make a massive difference, not very expensive on materials and nottoo messy - almost zero if you cut the PB and celotex outside and scrim+fill+paint rather than skim.

[meow2222]

to heat up. I replaced the tiddly radiator but I still have trouble heating it up tin the winter.

thinking of pulling down the ceiling and putting up some Kingspan and reboarding.

work out what the depth was and I'm unsure of the construction.

lathes/batons between the joists and the plasterboard?

Unless you're desperate for headroom, just board over the ceiling with PIR insulation. Another option is to blow insulation into the existing cavity through a row o holes & fill, but there can be issues that way.

NT

[charlieviking]

to heat up. I replaced the tiddly radiator but I still have trouble heating it up tin the winter.

thinking of pulling down the ceiling and putting up some Kingspan and reboarding.

work out what the depth was and I'm unsure of the construction.

lathes/batons between the joists and the plasterboard?

The flat is Victorian but I don't think the bedroom was part of the original construction, it's got a parque floor which I think was still popular up until the 1930s.

It's not a joist you can see, but one of the "lathes" (about 2mm thick, 30mm wide)

Yes, it has a paper covering

I agree.

[charlieviking]

Tim,

That makes quite a bit of sense, what's the best way to attach the celotex to the ceiling and then the plasterboard to the celotex?

Charlie Charlie

[charlieviking]

to heat up. I replaced the tiddly radiator but I still have trouble heating it up tin the winter.

thinking of pulling down the ceiling and putting up some Kingspan and reboarding.

work out what the depth was and I'm unsure of the construction.

lathes/batons between the joists and the plasterboard?

insulation. Another option is to blow insulation into the existing cavity through a row o holes & fill, but there can be issues that way.

What are the main issues with blowing insulation into the cavity, is it things like ventilation etc?

[Tim Watts]

Either screws and insulation washers (40mm or so dia plasticor thn metal washers) through into the joists. The screw the PB through the lot with extra long drywall screws.

Or - if you can support the insulation, you can bond it up with drywall foam (low expansion foam in a can).

Personally I reckon screws will be simpler.

[Tim Watts]

Yes - primarily ventilation.

[meow2222]

struggle to heat up. I replaced the tiddly radiator but I still have troub= le heating it up tin the winter.

f. I was thinking of pulling down the ceiling and putting up some Kingspan = and reboarding.

and to work out what the depth was and I'm unsure of the construction.

se lathes/batons between the joists and the plasterboard?

PIR insulation. Another option is to blow insulation into the existing cavi= ty through a row o holes & fill, but there can be issues that way.

hings like ventilation etc?

You've got no VB on the warm side of the insulation, causing a small risk o= f condensation and rot. You could of course stick or paint a VB onto the ce= iling. You also can't see into the cavity clearly or control the final posi= tion of the insulation accurately. And you need to make sure the roof is ke= eping water out effectively - eg unfelted slate roofs let water in, but the= n let it evaporate out, and blown insulation can trap the water. So its qui= te doable, but best check for the gotchas.

NT

[Phil L]

Because it was built with lath and plaster, then boarded over decades later, probably due to a leak, considering it's a flat roof

Better to fit insulation over what's there than pull it all down - find the joists and mark them in lines on the ceiling, you can use insulation backed plasterboards screwed up with 4 or 5 inch drywall screws.

If you decide to pull it down, you don't need kingspan, just use normal loft insulation stuffed into the voids and board over.

[David WE Roberts]

Loads of good advice already.

One thing, though. If you have a flat roof and evidence of some possibly non-standard work in reboarding the ceiling then there is a small possibility that there has been a problem in the past which has been covered up. In which case it might be worth investigating further.

If you are going to put up some PIR then plasterboard over that then state of the original ceiling isn't going to matter much so it may be worthwhile taking out a small patch of the ceiling all the way up into the roof just to check for signs of previous water penetration and any signs of rot.

You already have a small hole as shown in your picture so enlarging that enough to get your head through shouldn't be too difficult or too messy.

As already stated by others, the thin bits of wood in your picture look a bit like laths but they should be at right angles to the joist, not parallel, so a bit of a puzzle.

Remember to locate all your joists and mark both ends of each joist on the end walls (below the level of the new ceiling). Then you can snap a chalk line between the two marks when your new ceiling is going up and easily see where to put your screws through the PIR and then the plasterboard.

HTH

Dave R

[harry]

gle to heat up. I replaced the tiddly radiator but I still have trouble hea= ting it up tin the winter.

as thinking of pulling down the ceiling and putting up some Kingspan and re= boarding.

o work out what the depth was and I'm unsure of the construction.

hes/batons between the joists and the plasterboard?

Flat roofs have massive heat losses if uninsulated.

Before you start, you need to check the condition of the (external) flat roof. They have a limited life especially if made of bitumous felt.

Felt roofs are knackered in ten-fifteen years depending on how well the job was done in the first place..

If the roof is bad, you might find it better to take it off and replace, putting your insulation in from the outside.

It will save the mess and redecoration inside too.

[charlieviking]

uggle to heat up. I replaced the tiddly radiator but I still have trouble h= eating it up tin the winter.

was thinking of pulling down the ceiling and putting up some Kingspan and = reboarding.

to work out what the depth was and I'm unsure of the construction.

ic.com/29w4hmg.jpg

athes/batons between the joists and the plasterboard?

Thanks for the advice everyone, the flat roof isn't in that bad condition, = not signs of leaking and I've seen worse.

I think, as per the advice, I drill a few holes shove a camera up and take = some photos just to check. Either way I definitely think I'll just shove so= me 50mm PIR onto the existing ceiling and then some plasterboard.

Charlie