Best way to fix a flat leaky garage roof?

emb7March 6, 2007

Just bought a new house. The detached large 2 car garage has a very very leaky flat roof that is dripping inside of it (walls will be ripped out and wood treated once roof is fixed). One quote is $2500 to tear off and replace the flat roof (could go up depending on what they find underneath). Another is $4600 to tear off, build a 6 inch pitch and re-roof. We don't want to spend a ton, it's a garage. But also don't want to deal with it over and over. The flat roof co. does offer a 10 yr warranty. But can a flat roof ever stay waterproof? Any advice is MUCH appreciated. We're in Portland OR so it rains quite a bit. :) Thank you!

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Even if it's very leaky, it might just need fairly minor some repairs. First thing I would do is climb up there and take a look yourself. Maybe it just needs some patching, which you could do (or get a handyman to do). For example, if there are some open cracks or seams, you might buy a gallon or so of plastic roof patching compound, some gloves, a roll of fiberglass mesh and a margin trowel (small square-ended trowel). Cover any cracks with it and move on.

But you can do either of what you mentioned. Perhaps you have some slope up there already, even if just a little? If so, it's probably sufficient to just have it redone without adding any more pitch.

Roofs can last a long while, but need a periodic check and perhaps a minor touch-up every once in a while. Weather and sun do take their toll over time.

On another note, I once ate at the Joel Palmer house in Dayton. Very nice (not cheap either) restaurant especially if you appreciate mushrooms. Ever heard of it?

    Bookmark   March 6, 2007 at 3:25PM
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Don't know the Palmer house but love that winery area!

Our inspector and 3 roofers have said it's a bad roof. So we're willing to tear off and replace, just concerned if replacing it as a flat roof again will cause angst every few years. Would like to option to have a shop in there some day.

    Bookmark   March 6, 2007 at 8:13PM
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You didn't say what kind of roofing is on the roof so it is not possible to suggest how to repair it.

If it is a "low-sloped" roof (no roof should be flat) and the existing roofing is something like built up asphalt, the most cost effective thing to do is to cover it with wood fiber "recovery board" and apply a fully-adhered synthetic single-ply membrane like EPDM, PVC, etc. That should be easy to maintain and last as long as any other kind of roofing. The roof should slope at least 1/4" per foot and have no low spots for water to pond. To increase the slope, tapered insulation is one possibility.

    Bookmark   March 7, 2007 at 7:22AM
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What did the inspector say about it? What type is it? How old? If the substrate is solid and there is not a bunch of moisture present. I would look into a SPF(foam) roof being applied. Look in the phone book and see if there are any roof contractors that specialise in foam roofing.

I would contact them all and have them come out and give you a inspection and quote.

With foam there is no tear off and the foam is seemless. They also put on a 30mil coating. Usually a acrylic, which can last 10 years. The cost is about $4 per sqft for 1.5 inches of 3 lb foam and 2 coats of 1 gal per sqft primer and a final coat of 1.5 gal per sqft top coat. Both BASF and Henry have excellent systems. Just be sure your contactor has experience and is accredited. Also your roof must be sound and free from trapped moisture.

Foam is a great alternative because it is seamless and can be recoated and there are many foam roofs in commercial enviroments that are 30 and fourty years old. In fact the Lousiana Superdome was just fitted with a SPF roof after Katrina. I also have a SPF roof on my condo done this last October. I think it is a great alternative for flat roofs.

    Bookmark   March 11, 2007 at 3:59PM
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Here is a pic of my SPF roof done in Oct'06. The specs are what I described above and the top coating is Permex 115 with #8 granules broadcast in the finish for durability. The white color reduces tempetures dramatically and meets Cool roof guidelines.

    Bookmark   March 11, 2007 at 4:28PM
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