Insulate on top of concrete floor before carpeting
- Thread starter Tingly
- Start date
Sponsored Links
And here’s another one….bit random. I have had thick insulation (the stuff they roll out) in the loft. Now i cant walk on it! So, i just looked up pir after your post. Could i lay bits of pir board down up there on top of the existing insulation, and walk on that? Is it sturdy enough do you reckon? Thanks again
- Joined
- 7 Sep 2022
- Messages
- 2,745
- Reaction score
- 699
- Country
PIR is generally just a sheet of rigid foam that doesn't adhere to anything. It tends to be mounted on and/or between a wooden stud framework. You might not necessarily need or want to extend every socket through the PIR, instead just replacing a section of the wire that serves several existing sockets with a new wire that serves many sockets on the room side of the PIR. Such is one of the ballaches of installing IWI, compared to EWI (which also has its troubles
If you insulate the walls of adjacent rooms you then office room won't lose as much heat into the adjacent ones but don't fall into the trap of thinking that insulating something makes it warmer; heating makes it warmer, and insulating it means less of the paid-for heat leaks away so over time less heating input will be required. This doesn't necessarily make it warmer (that depends on the thermostat) but it makes it cheaper (or if you carry on spending the same amount it would be warmer, but we tend not to control warmth in that way)
I wouldn't personally use PIR/PUR under carpet directly; it's rigid but it wouldn't resist the deformation of someone walking on your floor in heels, for example. If you want to put PIR on the slab and lay a floor covering on it I would consider laying or adhering some 9mm OSB at least
You can't walk on anything laid on top of wool insulation. It needs to be fluffy to trap air and do its work as an insulator. Typically we install short legs into a loft and board on top of those (google Loft Legs) to retain the wool, or we make an assessment as to how much PIR is needed to replace the wool (PIR is typically thermally equivalent to wool 50% thicker so wool 150mm thick could be replaced by PIR 100mm thick) and have the walking area boarded out with PIR underneath and reuse the wool somewhere it can remain fluffy. You'd ideally leave the wool that is between the rafters in place, trimming it so it doesent stick up too much if eg 75mm rafters have been laid with eg 170mm wool (if you compress it too much with the rigid board on top it will put undue pressure on the ceiling plasterboards). The PIR is rigid enough to withstand occasional traffic when in contact with ceiling joists directly
If you insulate the walls of adjacent rooms you then office room won't lose as much heat into the adjacent ones but don't fall into the trap of thinking that insulating something makes it warmer; heating makes it warmer, and insulating it means less of the paid-for heat leaks away so over time less heating input will be required. This doesn't necessarily make it warmer (that depends on the thermostat) but it makes it cheaper (or if you carry on spending the same amount it would be warmer, but we tend not to control warmth in that way)
I wouldn't personally use PIR/PUR under carpet directly; it's rigid but it wouldn't resist the deformation of someone walking on your floor in heels, for example. If you want to put PIR on the slab and lay a floor covering on it I would consider laying or adhering some 9mm OSB at least
You can't walk on anything laid on top of wool insulation. It needs to be fluffy to trap air and do its work as an insulator. Typically we install short legs into a loft and board on top of those (google Loft Legs) to retain the wool, or we make an assessment as to how much PIR is needed to replace the wool (PIR is typically thermally equivalent to wool 50% thicker so wool 150mm thick could be replaced by PIR 100mm thick) and have the walking area boarded out with PIR underneath and reuse the wool somewhere it can remain fluffy. You'd ideally leave the wool that is between the rafters in place, trimming it so it doesent stick up too much if eg 75mm rafters have been laid with eg 170mm wool (if you compress it too much with the rigid board on top it will put undue pressure on the ceiling plasterboards). The PIR is rigid enough to withstand occasional traffic when in contact with ceiling joists directly
Last edited:
Sponsored Links
- Joined
- 7 Sep 2022
- Messages
- 2,745
- Reaction score
- 699
- Country
ps; when I said "doesn't adhere to anything" I meant "supplied without any form of attached adhesive" rather than "cannot be adhered to anything regardless the adhesive". PIR might typically be bonded to other surfaces using an expanding foam, though foiled-surface boards don't adhere as well as paper faced boards
Thanks Robin. Ps. You know the loft. After i remove the bits of roll insulation to form a path,If i get the thickness of the board so it actually comes level with the rafters (the strut things on the floor), is that what you mean would be safe to walk on.? Or would that need pleywood just placed on top ? (Dont really want to screw it down if poss, )Theres nothing up thereapart from a boiler and security camera hub thing, (and wasps!), so only go up maybe 2 times a year. Thanks
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
