Spray foam on asbestos roof

[Pasty]

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]

@grainboy

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

You could possibly oversheet it.

 

[Pasty]

@grainboy

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

You could possibly oversheet it.

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

 

[grainboy]

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]

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]

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

 

[Pasty]

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

 

[solo]

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]

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.

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]

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

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]

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 ££.......