Airtightness under carpet - what tape for hardboard

BoardsMember

I've finally caved, Mrs BoardsMember wants carpet in the front room and she's going to get it - she refuses to go through another cold/draughty winter.

We're laying carpet on draughty floating floorboards, room is 4m x 4m. I plan to put down thin (3mm) hardboard for draughtproof, then good quality underlay for insulation, then thick pile carpet for insulation/warmth.

We plan to do a significant renovation but it is not happening in time, carpet will be re-used after renovation so it is a reasonable compromise before doing a proper insulation job as part of the renovation.

So, the question I have is - what tape should I use to seal joints of the hardboard, and to seal hardboard to the skirts? There are a plethora of products out there, some that seem ridiculously expensive. I'm not looking for passive house outcome, just want to do a reasonable job before I put the underlay and carpet down. Any links or names of products that will get the job done would be great.

Calahonda52

How long will it be down?

BoardsMember

Calahonda52 wrote: »

How long will it be down?

2 answers...if we find it cosy with this approach, maybe 10 years+, we could leave it out of the refurb and save money.

If not, we'd do the job proper within 12 months.

Calahonda52

I would use the correct tape around the edges and maybe something like silage tape for the rest

BoardsMember

Calahonda52 wrote: »

I would use the correct tape around the edges and maybe something like silage tape for the rest

Thanks. Can you suggest products or where I go to find what the correct tape is? There are so many products out there and I dont want to buy something not fit for purpose.

BryanF

Are you lifting the skirting? Will the carpet guys damage a taped perimeter if you don’t ?

Wpuld the 3mm hardboard be worth it or would ply be as handy? If you were buying ply Would you just lift the floor and screw down fresh glued ply?

What if, before you put down the ply, you stuff insulation between the joists and lay an air-tightness membrane over top, then seal that with Contega tape to the perimeter.

Great job, air-tight, insulated floor, and as long as you’ve subfloor vents you have the 10year solution that you looked for.

BoardsMember

BryanF wrote: »

Are you lifting the skirting? Will the carpet guys damage a taped perimeter if you don’t ?

Wpuld the 3mm hardboard be worth it or would ply be as handy? If you were buying ply Would you just lift the floor and screw down fresh glued ply?

What if, before you put down the ply, you stuff insulation between the joists and lay an air-tightness membrane over top, then seal that with Contega tape to the perimeter.

Great job, air-tight, insulated floor, and as long as you’ve subfloor vents you have the 10year solution that you looked for.

Thanks for the response.

Not planning on lifting the skirting. Or the current floor. It's a quick, clean interim solution really. I know that carpet layers are likely to pierce the airtightness, but with good quality thick underlay and compared to what we have at the moment, it'll be a really good job.

I could even use some sort of silicone or caulk to seal the perimeter.

BryanF

Polytene, duct tape, silicone.

BoardsMember

BryanF wrote: »

Polytene, duct tape, silicone.

Sorry, not sure about the "polytene"?

BryanF

BoardsMember wrote: »

Sorry, not sure about the "polytene"?

polythene

BoardsMember

BryanF wrote: »

polythene

Sorry, I'm being thick now, I know, but what am I using the polythene for? I thought the job was 3mm hardboard, tape the joints, seal edges to skirts with silicone.

monseiur

Good quality 'Duct Tape' should do the job, there's 50 metres in a roll and it's 40 to 50mm wide, costs around a fiver a roll.
Before adding an extra board + underlay + carpet to existing floor ensure that the door will have enough clearance to open If you have a high door saddle it should be OK

sydthebeat

BoardsMember wrote: »

Sorry, I'm being thick now, I know, but what am I using the polythene for? I thought the job was 3mm hardboard, tape the joints, seal edges to skirts with silicone.

if you put underlay down and it acts as insulation, you risk condensation forming on the cold side, directly on the hardboard.

3mm MDF will bubble and disintegrate over time.

The polythene will (should!) stop the warm room vapour from reaching the cold mdf and condensing.

Note though that if the condensation point turns out to be on the warm side of the underlay, due to compression etc, then you could actually end up with staining and mould growth on the carpet itself.

the proper job is to lift the floor boards though... anything else is just lipstick on a gorilla.