Has anyone ever laid intello plus over timber floor and ?under carpet? I’m following an informal plan suggested in a People Powered Retrofit consultancy. I wonder if I’m missing a step. It was going to be:
Lay intello on floorboards and behind skirting, taping the joins and perimeter with tescon. Perhaps a bead of orcon on the floor at the perimeter to hold the membrane flat.
Carpet gripper: protect each nail with a blob of orcon before hammering it in (somehow)
Then thick underlay and carpet fitted by the carpet retailer
Im wondering if i ought to add a hardboard layer above the membrane both to protect the membrane and receive the carpet fitters nails and staples
Hardboard may give a more durable finish than the membrane but it needs nailing down approximately every 50-75 cm in a grid across the floor. That’s a lot of punctures to the membrane.
I’ve never seen or heard that advice before. I can see that it might work under a floating timber floor, although mine has the manufacturer’s recommended foil faced insulation underneath, which should be both air and vapour impermeable, apart from the edges.
I think this suggestion needs a rethink/second opinion and to come with full installation instructions and explanation.
Jonathan I have done this with Partel membrane and tape. I laid OSB on top of the membrane as protection. NB you will need to have insulation under the timber floor to prevent condensation forming.
I was worried that hardboard or plywood could be damaged by water spillage particularly in kitchen and WC.
Using a decent thickness of OSB over the membrane has the advantage that it doesn’t need fixing down and can be a floating floor, door undercutting will be needed to compensate for the increased height of the resultant floor.
Tongue and groove edges are best to avoid the different boards floating away in different directions, within the confines of the walls and any edging, as they expand and contract.
You could use marine ply in wet rooms but the price difference limits it to those areas
Thank you @Tim_Gilbert and @ian . Since i have no underfloor insulation I’m now very concerned about the risk of condensation above the membrane. So I’ve cancelled the carpet installation while I take stock and have a rethink. I taped the membrane before starting this thread so that’s how it stands now.
I’ve contacted PPR (People Powered Retrofit) but not had acknowledgement of receipt of my messages. Meanwhile I’ve listed my thoughts and options in a 2-page Word document. To avoid overwhelming you, here is a summary.
Option A: carry on regardless - membrane is vulnerable to damage; risk of condensation
Option B: Remove membrane except at perimeter - Reduces condensation and membrane damage risks, at the expense of airtightness quality
Option C: fit OSB layer above membrane - protects membrane, but does nothing for condensation risk I think
Option D: fit underfloor insulation - the proper solution, but high effort and extends disruption to house
The general appetite for Option D in the household is low, leaving Option B as my risk-averse and minimal disruption favourite option
I have read the full document as any reply to the summary might be inappropriate with partial information.
You have put yourself into a tricky situation by proceeding with the membrane at too early a stage. What seemed like a quick fix for a more comfortable winter now seems to carry a risk that you weren’t expecting.
The crawl space is too small for reasonable working. If you proceed from below you will gradually be closing off your air supply as you work, so quite apart from any other problems I wouldn’t do it.
As there is familial dissent on floor insulation you are lumbered regarding improving the floor in other ways unless you fit a highly permeable airtightness membrane, which will need to be discarded if insulation is fitted underneath. If you are lucky you may be able to relocate it to under the insulation but you will be lucky not to damage it.
Meanwhile, you need to prioritise the MVHR to get the humidity under control, preferably with a linked humidity sensor on the living room floor.
The advice I was given by Partel was to have at least 2/3rds of the insulation on the cold side of the membrane.
If you are insulating underneath the floor boards you need to ensure there is still good air flow in the void. We found we had a dead (un-ventilated) area where mold growth occurred.
Very few premises have air bricks in the ideal locations for complete ventilation of the whole underfloor area. There are always stagnant air pockets but whether they result in mould is dependent on other circumstances.
Sound like a bit of a conundrum - as usual with retrofit! I would personally suggest going the more arduous route and consider option D. There’s someone I’m helping at the moment based in Manchester who is doing exactly that, maybe worth you having a site visit there and seeing what’s involved and how it’s being done to clarify your thoughts?
Hi Jonathan, good to hear that you’re ploughing on with your retrofit. I’ve only just seen this thread so hope you’ve got a nice warm and dry floor by now.
If you’re still undecided - I’m having your option D, underfloor insulation, fitted (thanks to @Eric_Fewster), and if you’d like to see what it looks like you’re welcome to pop round before boarding goes down on top of the airtightness membrane next week.