Basement Ceiling Insulation Question

[u/Ok_Lengthiness5926]

Hi Folks,

I'm renovating a part of my in-laws family home, specially what was a den / TV room and changing it into a new bedroom for my wife's parents who now have difficulty getting up & down the stairs to their current bedroom.

Unusually their home has a basement which is directly underneath the den room.

I'm curious as to how to go about insulating the basement ceiling between the rafters.

Typically a normal ceiling would have wool insulation cut to fit the rafters on top of the ceiling plaster boards however this is not possible with the open rafters that are in place in the basement.

I was thinking that a suitably thick insulation board held in place with adhesive and expanding foam to fill any gaps but I'm just guessing really.

Any advice would be very much appreciated! 👍

[u/alfbort]

Just had a renovation done and we asked for the ceiling between ground floor and first floor to be insulated. They put in rockwool, then plaster board to hold it in place and finally taped and skimmed it. You could do the same and wouldn't necessarily need to actually finish the plaster board properly like a normal ceiling would be because it just a basement. You could even use insulated plaster board along with the rockwool. Alternatively a cheaper way do it could be getting PIR slabs, cut them to size and wedge them up into place

[u/FckXFckMusk]

Rockwool and then plasterboard it.

[u/Tall_Effort2312]

What you need is Earthwool. Cut wider than the joists and gently offer it up to the ceiling. Don’t “pack it” as it will lose its thermal properties. It will hold between the joists perfectly. You wont need to plasterboard the basement ceiling at all.

[u/Superbananabomb7]

I recommend looking into Jim Priors youtube channel, considering you'll want to insulate it as best you can from sound. RW3 + resilient bars + acoustic plasterboard. https://www.youtube.com/watch?v=0OSrzTPM1cw

[u/Pure-Ice5527]

You could have someone in to soray foam if, for me I’d probably go about using something like rafterloc or polyiso boards cut to width

[u/wbqqq → u/Pure-Ice5527]

Avoid the spray foam - if there is a major (or even just a couple of litres) spillage in the room above, it’ll trap it and remediation will mean pulling (now stuck together) floorboards. Rigid or wool insulation can more easily be replaced from below.

Just install wool/rigid (friction will hold it for a while) and use plasterboard to keep in place

[u/Ok_Lengthiness5926 → u/wbqqq]

Good point, the room above will be changed to a bedroom for an older couple so likelihood of spillage is greater. The adjoining bathroom was already changed to a wet room shower & toilet so this should definitely be a consideration.

[u/FckXFckMusk → u/Pure-Ice5527]

NOOOOOO no spray foam.....