Roofer needing advice, flat roofing question.

Regencyroofingipswich · 10 Jan 2011

Hi guys, i am normally on here answering and helping others but today i have a problem that has actually stumped me for once.

We done a detatched garage roof in november, the roof originally had corrugated asbestos sheets nailed directly onto timber rafters, the pitch of the roof is well over usual flat roof pitch at about 7-10 degrees.

We stripped the sheets and installed 18mm plywood , then installed a 3 layer torch on felt roof with 1 3b layer, a 2mm underlayer and a 4.5 capsheet.(all staggered joins of course), new upvc fascia and gutter. All felt joints were fully bonded and beaded with a healthy layer of bitumen squeezing out of the joints.

Got called back to the job tonight, customer says its leaking but cannot find anything wrong with it at all, its perfect.

The boards seem to be damp on the underside all over the entire garage (6m x 3m ). My immediate thought is that it is condensation but there is no heater in the garage or tumble dyer. Is it still possible for it to condensate with no heating ? My other thought is that i seem to recall the boards getting wet when we were laying them so could it be the damp in the boards pushing back out as they dry. ? Confused as in 16 years have never had a single leak in a flat roof one by me !

flatroofer666 · 10 Jan 2011

Regencyroofingipswich said:
Hi guys, i am normally on here answering and helping others but today i have a problem that has actually stumped me for once.

We done a detatched garage roof in november, the roof originally had corrugated asbestos sheets nailed directly onto timber rafters, the pitch of the roof is well over usual flat roof pitch at about 7-10 degrees.

We stripped the sheets and installed 18mm plywood , then installed a 3 layer torch on felt roof with 1 3b layer, a 2mm underlayer and a 4.5 capsheet.(all staggered joins of course), new upvc fascia and gutter. All felt joints were fully bonded and beaded with a healthy layer of bitumen squeezing out of the joints.

Got called back to the job tonight, customer says its leaking but cannot find anything wrong with it at all, its perfect.

The boards seem to be damp on the underside all over the entire garage (6m x 3m ). My immediate thought is that it is condensation but there is no heater in the garage or tumble dyer. Is it still possible for it to condensate with no heating ? My other thought is that i seem to recall the boards getting wet when we were laying them so could it be the damp in the boards pushing back out as they dry. ? Confused as in 16 years have never had a single leak in a flat roof one by me !

iff they park the car in there at night then the hot engine can and will condensate on the cold underside of boards during the recent cold spell...its happened to me mate and my roofs never leak also

^woody^ · 10 Jan 2011

You only need a degree or two temperature difference for condensation

A leak will most likely have definite runs and concentrations, whereas condensation will be more even over the whole underside

If you put no insulation in, then the cold deck will be very susceptible to condensation from any unheated garage.

Regencyroofingipswich · 10 Jan 2011

Thanks guys , im pretty sure it is condensation as its all over the 6m x 3m span top and bottom but its pretty wet!

Ill go back tommorrow and have another look in daylight and reassure myself.

Nothing worse than a comeback on a job, i worry all evening about it!

datarebal · 11 Jan 2011

Very likely As said condensation, seen the same on stable blocks too.

SASroofer · 11 Jan 2011

Yeah from your description of the water covering all of the ply, and you being an experienced flat roofer, it has to be a condensation issue.

Try suggesting to the customer to leave a window slightly ajar for aweek, see if theres any difference.

smashngrab · 12 Jan 2011

What so the condesation is forming on the first layre of tar on the first sheet that was layed ?

Only i did a valley in torch on and there was wet stains on the plasterboard that covered the wooden beams that support the center valley. I checked the joints they looked good but i torched more felt over each joint to make sure.

They said it was still damp,so i covered the whole lot in Acropol.This did the trick,but i always thought it was conden forming under the felt.And by covering it all in Acyropol i kind of insulated the felt.

Alastairreid · 12 Jan 2011

smashngrab said:
What so the condesation is forming on the first layre of tar on the first sheet that was layed ?

No, its a flat roof and there appears to be a condensation issue on the underside of the plywood decking.

Regencyroofingipswich · 12 Jan 2011

Only i did a valley in torch on and there was wet stains on the plasterboard that covered the wooden beams that support the center valley. I checked the joints they looked good but i torched more felt over each joint to make sure.

They said it was still damp,so i covered the whole lot in Acropol.This did the trick,but i always thought it was conden forming under the felt.And by covering it all in Acyropol i kind of insulated the felt.

This sounds horrible.
You really did this to someones roof and got paid for it ??

Alastairreid · 12 Jan 2011

Regencyroofingipswich said:
This sounds horrible.
You really did this to someones roof and got paid for it ??

Keeps us in work

Regencyroofingipswich · 12 Jan 2011

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smashngrab · 13 Jan 2011

Do you know what,it must be wonderful to be as good as you people.The people who never have a come back.I asked a question,but all you could do was take the ****.Fk u.

PS I'd never wear a jacket like that.

Alastairreid · 13 Jan 2011

smashngrab said:
Do you know what,it must be wonderful to be as good as you people.

It is!

SASroofer · 13 Jan 2011

smashngrab said:
Do you know what,it must be wonderful to be as good as you people.

You mean instead of the dirty bodging cowboy that you are? Yes, it rather is

In response to your question, your problem was more likely poor workmanship tbh.

Regencyroofingipswich · 13 Jan 2011

smashngrab said:
Do you know what,it must be wonderful to be as good as you people.The people who never have a come back.I asked a question,but all you could do was take the p**s.Fk u.

PS I'd never wear a jacket like that.

Maybe not that jacket but the hat would suit you just fine....

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Roofer needing advice, flat roofing question.

flatroofer666

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