Remedy of Exisitng flat roof of canopy water leakage

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Remedy of Exisitng flat roof of canopy water leakage

Postby j5v55 » Tue May 25, 2010 7:31 pm

Existing canopy (about 30' x 100') at the patio has water leakage issue.
The ceiling is finished in sheetrock. It's built 15 years ago w/ wood joist structure.

In between beams supporting roof, each of the exterior plywoods seems like sagged in overtime, and water stays on the area.
Water leakage spotted on the areas (total 4)

Original roof structure is sheet roof membrane over exterior sheathing.

How do I level those existing roof condition and provide proper waterproofing?

The best way is to remove all existing roof and level with slopes, however, contractor resists due to his budget issue.

Please share your experience
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Postby cousinbirgco » Tue May 25, 2010 8:07 pm

Hello j5,

You need to supply a little more information including the size of the rafters (2 x 10 or ?), the distance or length from bearing wall to bearing wall (16 ft long or ?) and spacing of the roof rafters (16 or 24 inches on center or distance between each rafter). It sounds like the plywood sheathing is not thick enough to bridge the span of the roof rafters so it is sagging between the rafters.
The best way to fix it is to rip off the existing roof and sheathing and then assess the structural strength and requirements of the rafters. The roof, even if "flat" should be pitched at least 1/4 inch to the foot to drain water off the finished roof membrane or whatever roofing material you decide to cover it with. The plywood sheathing also needs to be thick enough (rated for span of the rafters) so you do not get any deflection to collect water. The flashing of the flat roof where it meets the house exterior wall is also critical. This should be replaced, preferably with copper so it can be bent and soldered if needed to make a water tight seal.

Going over the existing roof will be a waste of time and money and will probably compound the problem or even create more severe structural issues. Good luck.
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Flat Roof water leakage

Postby j5v55 » Wed May 26, 2010 1:17 am

Thanks for sharing your experience.

I don't have any room to provide roof slab even 1/8" per foot because the joint between existing flat roof on top of canopy and building is just flushed.
There's no elevation difference.
The building roof is gabled.
And canopy roof is flat....

here's the problem........
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roof image

Postby j5v55 » Wed May 26, 2010 1:19 am

image
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Postby cousinbirgco » Wed May 26, 2010 6:09 am

You can post an image from a photo website like webshots or similar.
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Postby phansford » Wed May 26, 2010 7:50 am

The big misnomer about flat roofs are that they are flat. They are not. All roofs MUST have a slope. Otherwise you get the situation you are experiencing.

Based on what you are saying, I don't think I need photos to tell you the addition (porch canopy) needs to come off. Completely. While you might not see signs now, it could cause problems in the main house.... if water is able to track back toward that house.

If you can post photos... then we can give you a definitive answer.
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Postby djswan » Wed May 26, 2010 4:40 pm

Whoops, sorry about the double post. :)
Last edited by djswan on Wed May 26, 2010 4:44 pm, edited 1 time in total.
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Postby djswan » Wed May 26, 2010 4:42 pm

Sounds like something I went through. Nominal 2 x 12 x 24. nailed together 24" oc and 24' span on a flat slightly saggy roof, actually still crowned up last time I checked (so far so good) and at least there isn't drywall underneath nice painted plywood. I can't stand drywall.
Shaped rigid insulation to form pitch on roof as suggested by owner and roofing/insulation contractor...That deal went a little sour between those two and next thing was some urethane dude spraying stuff all over the place. ARGGGGGGGGHHHHHHHHH!!! The building looks beautiful and she's stout.
It has that going for it too.

A nice light over-frame would have been so delicious but...

Build a water catcher on top and live the dream, that's my advise.
How you get there... eh....

and yes I agree, that there is no such thing as a flat roof. :D
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Postby cousinbirgco » Wed May 26, 2010 6:56 pm

phansford, how are ya?

thought you were either abducted by an alien or on sabbatical
in Tibet,

and I figured you wouldn't fall into the architect vs. building designer
cabal, although your comments would be interesting........ :shock: :D
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Postby phansford » Wed May 26, 2010 8:10 pm

DJ - I was thinking the same at first... you could get some sloped insulation, but in the end that could be a nightmare.

cousinbirgco wrote:phansford, how are ya?

thought you were either abducted by an alien or on sabbatical
in Tibet,

and I figured you wouldn't fall into the architect vs. building designer
cabal, although your comments would be interesting........ :shock: :D


I have been reading your posts on the house... but page 11 of that thread doesn't come up for me... strange. I am assuming the house is complete and your just posting photos of various details for the end of construction

I've had the nose to the grindstone.... I have a bid opening tomorrow for Phase Two of a homeless shelter for men. And I have a couple other projects I need to get out to bid. Things seem to be picking up. I think part of it is deferred maintenance and capital project.

DJ- What is happening out west... are you staying steady....pick-up in work...... what the market like for the custom Timber Frame stuff right now?
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Postby cousinbirgco » Wed May 26, 2010 9:10 pm

phans,

Glad to hear business has picked up, work in our area has also improved a bit. Currently on a major renovation project on a barn/carriagehouse built in 1843, converted to a residence around 1910. You would appreciate the massive beams, mortise and tenon/wood peg construction and I think that feller DJ might call it a timberframed barn. :)

Our place is basically complete with mostly detail work to go.
I am posting some finish work photos towards the end of the project and I expect to go into further details of the energy consumption/conservation results as summer approaches. Winter heating performance was very good, especially after the solar hot water panels were operating. I need to check page 11, think it needs another post to push it forward a bit.
Good to hear from you and keep up the good work.
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Postby djswan » Thu May 27, 2010 9:56 am

Hey phan :D 8) Glad to hear anyone is working now. ahhhhhh 14% unemployment here in the Flathead Valley. The only local work I have been involved with was the school with the roof I described. The owners got divorced....and looks like the same is happening to me. Geez...I remember announcing the birth of my daughter on this forum almost three years ago.
I moved back to Montana 6 years agp with a million dollars worth of contracts from other states. We are still on the project in New York. Taking our time as it could always be the last project, we don't care about getting anything done fast nowdays, just right.
3% unemployment in the Dakatos and eastern Montana. It's booming there. I'm really trying to get away from the custom timberframing stuff and more towards the helping hand aspect of it as I see small home improvement jobs as bread and butter now. Case in point, this thread. :) AND of course trying to get architects thinking the same way. The architect of that school was fired and was a real jerk. He is the story of the architect who wouldn't paint a school. He is younger than me with a big giant ego that got him nowhere but losing his practice and the unemployment line and his family too.
Seriously thinking about writing a book or article about it.
I have found friends here and a place to rest my over-thinking head.

edit: Here's the reference.
http://www.flatheadbeacon.com/articles/ ... tale/8909/

and smiles to my cuzzes. :D
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Postby Guest » Sun May 30, 2010 4:12 pm

Works Picking up quite a bit in the UK too at the mo, I've just took on 2 apprentices ;p

I'd suggest stripping back the existing roof covering cut some firrings (timber to fall) to provide about a 1:40 fall, 1:20 would be nice but it would depend on the length of the span, fix them to the existing joists, running away from the building of course, you tend to find this method is alot cheaper than Insulation cut to fall. and a saves alot of labour time ;p, obviously then re-apply the foof covering, making sure that it's lapped correctly.
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