Spray Foam Loft Insulation

robertwhall

Hi, We are trying to buy a house (ours is sold and already lost one due to survey).We thought this one would be great, we love it however the survey has come back saying the whole loft has been sprayed with a spray foam loft insulation. I have never heard of this. I am told it can prevent mortgage lenders refusing to lend if we ever wanted to move again. I understand its been there about 18 years. Are there major pitfalls to this stuff. My understanding is that it cannot be removed - well unless you replace the roof. 
Thank you 
Robert

Lespaul1960

I had a phone call the other day from somebody trying very hard to flog it to me!!  So I would draw your own conclusions. needless to say I declined there kind offer..

eddddy

The problem is that the foam surrounds the roof timbers, meaning that if moisture gets in the timbers, the foam stops the timber from drying out.

That moisture can cause the timber to rot, and since the timber is encased in foam, you won't be able to see that it's rotting. So the first indication might be when the timber is so rotten that it fails, and the roof starts to collapse.

tacpot12

It is a really bad idea because it creates a barrier for moisture to leave the house. The house will be prone to damp, unless you have a mechanical ventilation system that covers the whole living area and as described above, it causes the timbers to rot as moisture they absorb can't evaporate into the loft space. 

Jeepers_Creepers

I think it's more fair to say that spray foam can cause these issues, but doesn't necessarily do so. 

If it's sprayed on to secure slates/tiles and forms a tight bond, water shouldn't get in there from outside to cause any issues. And the ventilation of the inside of the roof space is largely a separate issue which can be handled with its own vents (although in many cases the loft ventilation does also rely on the air percolating through the roofing membrane and tile gaps).

I certainly wouldn't proceed without establishing as clearly as possible - by an independent (possibly specialist) surveyor - that this roof is ok.  And if the foam was added in order to secure loose tiles/slates (what does the outside look like?), I would in any case be factoring in a roof recovering within a decade, and adjust my offer accordingly. 

Davesnave

I would just price in the assumption that the roof would be changed during my occupation. The end.

robatwork

As Dave said.

I pulled out of a house purchase because it had foam sprayed (badly) all over the inside of the roof. 

If you just factor in the price of a new roof, in fact get a quote now and take that off your offer, job done.

FreeBear

Jeepers_Creepers said: If it's sprayed on to secure slates/tiles and forms a tight bond, water shouldn't get in there from outside to cause any issues.

But the stuff will never get in to all the gaps, especially where the tiles/slates are in contact with the timbers. Where the foam does get between the timbers & tiles/slates, as it expands, it will lift the tiles (only a mm or three). This leaves a gap where water will get in and eventually cause unseen rot.

When the roof eventually needs replacing, the majority of the tiles/slates will have to be thrown away as they will be broken when trying to remove them. Those that don't get damaged will be caked in foam rendering them uneconomical to reuse (taking in to account the time to clean them).

Other reasons to avoid spray foam - It gives off toxic fumes as it cures. It will continue to outgas the fumes for a long while afterwards. It burns very easily, and once again, gives off yet more toxic fumes - Grenfell Tower was clad in the same stuff, look at how well that went up.

Mickey666

One area of roof on my house dates from the 18th century.  It had no effective sarking (membrane) and many of the pan tiles had gaps, meaning that the attic space was very draughty.  When I stripped the roof to install a breathable membrane I was quite surprised that the vast majority of the roof timbers were in good condition after so long - almost certainly because of the good ventilation within the attic space.   The one area of significant rot, and I mean almost complete disintegration of the timber, was around a chimney where some failed flashing had allowed rainwater to leak into the attic and into the bedroom below.  A previous owner had ‘fixed’ this leak with some expanding foam squirted through the bedroom ceiling.  While this bodge stopped rainwater emerging the bedroom, it caused the water to pool around some roof timbers, resulting in their complete disintegration.  Now imagine even a small leak of rainwater through a roof where the underside had been smothered in spray-on foam.  This practice is will destroy a roof through trapped moisture encouraging rot and, as noted above, because the problem is hidden from view the first signs of problems will probably be too late to repair and a new roof will be required. 

So I’d say the OP has two options;
1. Buy the house but put aside enough money to pay for a new roof
2. Walk, if not run, away and find an unmolested property

Jeepers_Creepers

Yup - fair do's!

greatcrested

Mickey666 said:

So I’d say the OP has two options;
1. Buy the house but put aside enough money to pay for a new roof
2. Walk, if not run, away and find an unmolested property

My thoughts too.