Under floor spray foam - problem for mortgage?

salsadiscodancer

I've been reading in the news about bank lenders refusing a mortgage for homes with loft spray foam insulation.

Does anyone know - does this also apply to spray foam installed below the ground floor? Or is it only roofs due to the warm air rising? We have a suspended ground floor, meaning there is a cavity below the wooden floorboards. We had Qbot in to spray the underside of the boards with foam. Now I'm worrying a) if it could cause any damp or rot issues and b) even if it doesn't, could the perception of problems make it harder to sell the house in future? As we only plan to stay here another 5-10 years.

Is there any way to check the state of the joists and floorboards without lifting them (which would break the foam installation and presumably could cause more problems)? 

theartfullodger

I'd not even consider spray under floor. Any (total) blockage to ventilation like this is IMHO very likely to cause any damp or rot issues. I owned 3 off 2-storey terrace houses in the highlands of scotland - ie cold, windy, low incomes - (on what the english call originally council housing estate, the Scots call a"scheme") & local housing association on someone's behalf. put in external insulation on outside walls ("cladding" in today's parlance) & under ground floor some fabric insulation (inch or two thick??) under the ground floor 2012-ish.  That worked well, tenants were v happy, heating bills dropped a lot & I got much improved outside appearance.  Think that's the way to do it.  Views of mountains & sea-lochs.. March 2014...


They employed small people to take up floor-boards and wriggle around under putting the insulation in 

ThisIsWeird

I'd have no concerns at all, SalsaD. That is a completely different scenario to that in lofts.
For lofts, the main risk is of any rainwater that gets past the roof covering being trapped under the tiles by the foam layer, and not being able to be either drained or ventilated away, therefore having time to cause rot to the rafters and battens. The problem is, you cannot see through the foam to tell if there is an actual leak/water/rot issue taking place.
Your floor is completely different, assuming you don't regularly spill lots of water on it that could seep through the boards? It'll also be thoroughly ventilated from underneath, and you'll have next to zero water vapour percolating through from the room above either.
I bet your between-joists foam insulation is the most effective solution possible, as it'll also stop draughts in its tracks.

Debbie9009

If I was looking for a house, I wouldn’t consider one with underfloor spray foam, purely because you can’t lift the floorboards, so if there is ever a problem with any pipes under the floorboards it’s going to make carrying out any work even more expensive.  

I’ve also had part of my ground floor flooded with a combination of heavy rain and a blocked drain, once the water cleared it dried out quickly, with no lasting damage, but I suspect underfloor spray foam would hamper that, so that’s another reason I wouldn’t consider it.  

ThisIsWeird

Debbie9009 said:

If I was looking for a house, I wouldn’t consider one with underfloor spray foam, purely because you can’t lift the floorboards, so if there is ever a problem with any pipes under the floorboards it’s going to make carrying out any work even more expensive. 

I’ve also had part of my ground floor flooded with a combination of heavy rain and a blocked drain, once the water cleared it dried out quickly, with no lasting damage, but I suspect underfloor spray foam would hamper that, so that’s another reason I wouldn’t consider it. 

If I was looking for a house, I'd choose this one over one without, all other things being equal. 

There is presumably a void under the floor joists, where pipes and cables are run? That's how the Qbot got in there in the first place.

Should any access be required from above, then lift a floor board, separating it from the foam layer, cut into the foam if needed, remove a whole section if required, do your work, make good the foam layer (aerosol can), and replace the board.

Unless I'm missing something, I see no real issues at all. And this should have transformed the floor insulation level.

Having now watched a video, the only annoyance is that they don't appear to seal between the end joists and the walls, so the biggest source of draughts - coming up under the skirting boards - is not eliminated. So that should be done from above, using mastic or similar.

FreeBear

Debbie9009 said: If I was looking for a house, I wouldn’t consider one with underfloor spray foam, purely because you can’t lift the floorboards, so if there is ever a problem with any pipes under the floorboards it’s going to make carrying out any work even more expensive.

I'd be more concerned about electric cables - Mice chewing on the insulation is a problem (all be it uncommon), and replacing damaged cables is a pain at the best of times. Throw in spray foam insulation, and the difficulties are compounded.

I wouldn't consider the stuff here as it would compromise air flow over the dwarf walls. In addition, there is no easy way to check that the job has been done to a satisfactory standard.

ThisIsWeird

FreeBear said:

Debbie9009 said: If I was looking for a house, I wouldn’t consider one with underfloor spray foam, purely because you can’t lift the floorboards, so if there is ever a problem with any pipes under the floorboards it’s going to make carrying out any work even more expensive.

I'd be more concerned about electric cables - Mice chewing on the insulation is a problem (all be it uncommon), and replacing damaged cables is a pain at the best of times. Throw in spray foam insulation, and the difficulties are compounded.

I wouldn't consider the stuff here as it would compromise air flow over the dwarf walls. In addition, there is no easy way to check that the job has been done to a satisfactory standard.

In the extremely unlikely event that a cable or pipe fails, then you run a new one under the joists. Or, you lift the floor and tackle it from above - just as you would currently. The only addition is cutting through the foam - big deal.

I would expect, tho', that any cables will not be sprayed over - they certainly shouldn't be. I'd personally be happy for pipes to be, tho'; better insulated, no creaking or knocking...