If you have a new account but are having problems posting or verifying your account, please email us on [email protected] for help. Thanks :)
Hello all! Please ensure that you are posting a new thread or question in the appropriate forum. The Feedback forum is overwhelmed with questions that are having to be moved elsewhere. If you need help to verify your account contact [email protected]

Floor insulation boards

  • 19-03-2023 7:22pm
    Registered Users Posts: 446 ✭✭

    I'm redoing the floors on the entire ground floor, I have a layer of concrete then under that I can only assume there is some insulation because it's a 2000s built house but then who knows.... Floors are straight. I have about 25mm thickness to work with here without needing to resize doors etc. half the house will be tiles half hard wood. Just wanted to check opinions:

    1. For tiled spaces, I'm thinking on top of the concrete floor lay adhesive, put 12mm tile backer board down, lay adhesive again then tiles, again 10mm thick. I'm assuming 2 layers of adhesive might add approx 3mm total? Should I account much more for adhesive? So might be 25mm, and what's the opinion on tile backer boards are they good? Key is insulation!
    2. For the wood part, I found a hardwood floor that's 15mm thick, and normally an approx 2mm foam goes on underlay as a base. I'm going to have some 10mm left (the tiled kitchen will be 1cm higher if I don't add another layer under the wood floor), are there any board equivalents, something I can add for insulation under hard wood floors?

    This is one potential that's advertised as under floor insulation, is this sort of stuff ok to work with? how do you make sure it doesn't move, shift under the floor?

    I'm fully aware I would be best to have 25cm kingspan under the floor but I've not much to work with budget wise I don't want to turn this into a poject. 2.5cm across the ground floor is perfect as I wouldn't have to mess with any stairs, pvc doors etc.


  • Registered Users Posts: 386 ✭✭grimeire

    for 2.

    You can get 6mm ply but you will be hard pressed to find much <10mm. You can get thicker cork underlay thats about 6mm in thickness and it has a foil backing. Personally i think you notice the difference between that and the pu foam underlay. It does keep the heat in better from what i seen. Are you sure the hardwood floor is 15mm tick. I laid a lot of floors in my time and it was rare i would find it below 18mm. Laments and semi solid floors would be around the 8mm-15mm range though. You have to remember here that you would need about 5mm clearance for the doors. I know you said the floors are straight but they rarely ever are.

    The insulation you have linked to is underfloor insulation and the minimum size that comes in is 25mm so you wont be able to use it in your case. Also note that stuff is expensive as i just bought 50 sheets at about €30 for a 25mm sheet and up to €75 for 150mm sheet.

  • Registered Users Posts: 446 ✭✭Kurooi

    This is ground floor , solid concrete underneath, can I use plyboard , thin foam then wood on top?

  • Registered Users Posts: 189 ✭✭lmk123

    Id say levelling compound then the thicker underlay and then the flooring, I think sheets of plywood would be a disaster under a timber floor, if you want insulation I’d suggest drilling a hole in the concrete and see what you have under it, if you don’t have enough under the concrete you’re certainly not going to improve the situation in a few mm on top of it, definitely consider bursting the floors and putting down insulation if it’s poor, now is the easiest and cheapest time you’ll ever get to do it