Pir on ceiling 1930s semi

[STORYTELLER]

Hi

Quick one.

Want to insulate upstairs ceilings below loft space as joists only 100mm. Ceilings may have asbestos plaster so would like to cover in c.20mm PIR (foamed or bonded in place, or some screws if not flat enough) then overboard with new pink plasterboard using c.70mm drywall screws into joists.

Anyone see any issues? Will be much cheaper and thermally better than same thickness insulated board.

Also thinking doing same on inside of exterior walls (solid walls) using adhesive on PIR to wall, then more on PIR to plasterboards, backed up with some hammer fixings maybe??

Experience or input much appreciated.

 

[Ivor Windybottom]

I did exactly this in our last house's ceilings. Made a huge improvement. No need to remove the plasterboard, in fact it will add strength and insulation.

Find the joist centres then mark their positions clearly and accurately on the walls. You'll need this when you're screwing the plasterboard up.

The one issue you do need to care about is whether you're overloading the joists. Need to check span and dimensions first.

 

[endecotp]

So you’re proposing 20mm of PIR because the joists are only 100mm deep?

Firstly, 100mm of rockwool is better than 20mm of PIR. Secondly, you can fill above the tops of the joists. Or have I misunderstood why you are proposing this?

What makes you think there may be asbestos in the plaster?

 

[Ivor Windybottom]

100mm is nothing by modern standards. More is always better.

I'm guessing pre-1980s Artex, which usually does contain asbestos.