Spray foam on asbestos roof

Pasty

Member

Location

Devon

• Feb 11, 2020

• #1

Got a big old shed with concrete fibre roof, quite old and failing in places. Probably asbestos involved. Problem I get is condensation. There are breaks in it too so I get leaks which come down to the farm office. Power lines overhead so replacement may be costly. Was looking at a 10 year fix with a couple inches of spray foam.

Questions are will this fix the leaks? Will it firm up the panels? It's all Big 6. When I come to replace the roof in full, will I regret doing the spray foam?

Anyone done used this system? Thanks.

 

KennyO

Member

Mixed Farmer

Location

Angus

• Feb 11, 2020

• #2

@grainboy

Not sure if it will fix it but it will certainly make the eventual replacement more costly.

You could possibly oversheet it.

 

Pasty

Member

Location

Devon

• Feb 11, 2020

• #3

KennyO said:

@grainboy

Not sure if it will fix it but it will certainly make the eventual replacement more costly.

You could possibly oversheet it.

Click to expand...

What, like for like? Seal it in? Problem is some of the timbers have suffered due to guttering failure.

 

grainboy

Member

Location

Bedfordshire

• Feb 11, 2020

• #4

Don’t do it,
will not seal the leaks, still let in water but hold it on the purlins and probably do more damage because it can’t dry,
On future disposal, it becomes a nightmare,
At present dismantling a large shed, job has overrun by approx 5 weeks on a estimated 6 week job, all down to bloody foam.
will never undertake one again, unless I’m paid a lot of money.

 

Shutesy

Moderator

Arable Farmer

Location

Essex/Herts Border

• Feb 11, 2020

• #5

Don't do it, just becomes a massive rodent magnet, they love to chew there way into it and nest in the roof.

 

simon-0116

Member

Location

Sheffield

• Feb 11, 2020

• #6

Water tracks in and pulls it off eventually.
Also a nightmare if wanting to run cables, water pipes etc

 

Pasty

Member

Location

Devon

• Feb 13, 2020

• #7

Thanks, looking into it, seems like a poor plan. What about oversheeting? Anyone done that?

 

solo

Member

Location

worcestershire

• Feb 13, 2020

• #8

If the power lines are under 3m from the shed the power company will move the wires free of charge due to H &S risk. Electric company will visit site and work with you to solve any H & S issue caused by their apparatus. I had a £35,000 underground cable system installed by western power due to 3 phase being only 1.5m above a building roof. Building was put up 1937. All I asked for was some sleeving so I could reroof it!
If it was me I would remove the old roof and put new on, provided the shed frame was sound.

 

melted welly

Member

Arable Farmer

Location

DD9.

• Feb 13, 2020

• #9

Pasty said:

Got a big old shed with concrete fibre roof, quite old and failing in places. Probably asbestos involved. Problem I get is condensation. There are breaks in it too so I get leaks which come down to the farm office. Power lines overhead so replacement may be costly. Was looking at a 10 year fix with a couple inches of spray foam.

Questions are will this fix the leaks? Will it firm up the panels? It's all Big 6. When I come to replace the roof in full, will I regret doing the spray foam?

Anyone done used this system? Thanks.

Click to expand...

did this in cold store.

The asbestos starts to laminate, goes porous and soft, then starts leaking.

the foam stops it breathing.

had to take it down last year after about 25 yr of foam.

maybe do as quick fix, but costly in long term.

 

KennyO

Member

Mixed Farmer

Location

Angus

• Feb 13, 2020

• #10

Pasty said:

Thanks, looking into it, seems like a poor plan. What about oversheeting? Anyone done that?

Click to expand...

Only heard it talked of never seen it done. Builder who works for a friend suggested it for insulating a single skin asbestos roof. Think he suggested timber battons/purlins over existing roof, Then fibre wool and then fixing box profile sheets over the top. Job was never carried out.

This would need sound purlins on the existing roof. It has the advantage of no absetos removal and disposal cost.

To fix leaks in some asbestos roofs we have had clear roof light sheets glued to the underside. This can work well.

 

Pasty

Member

Location

Devon

• Feb 15, 2020

• #11

Thanks again. I think the power lines must be under 3m over the roof. Will have a better look in the morning. I own all the land from pole to pole if it were to be trenched and that would be desirable.

I think the only answer is to do the full job. The A frames and rafters are fine but some of the side beams are rotten due to years of leaky guttering. I want PV on it long term so I guess I'll have to look into what's best for that. I like the look of these fully insulated steel roof panels that give you an instant finished job inside.

Just where to put all the stuff currently in there and how to come up with the ££.......