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Aarone1972 01-30-2012 11:58 PM

Low slope roof repair
I have a roof over my carport. It is about 25 feet long and 12 feet wide. It has a black roofing tar like coating (not a membraine) on it now. I have owned the house for about 5 years and have never done anything to it. It looks as if it has been put on too thick in that it has a lot of cracks in it. The cracks do not go all the way through. It may be a newer product rolled over old cracks, im not sure. There are some large blisters or bubbles in it (like 5 ft x 2ft). Although I would like to scrape it all off and do a membraine type roof, time and $ requre a simpler plan.

Here is my plan. Make some small holes in the blisters, use a caulk tube of roofing tar and pump it down in the hole in several locations, causing it to adhere to the roof structure. Than I will spread roofing tar over the entire roof.

Does that sound like a decent plan. The current roof seem to be working well without any leeks, however the current top layer seems too be gatting old and brittle.

I have seen white RV type roll on products that claim to have amazing elastic properties and last a very long time, should this be a consideration?

Your thoughts are greatly appriciated!


joecaption 01-31-2012 12:12 AM

Not going to work and will just end up costing you more money. You may think it's not leaking but I'd bet it's soaking into the sheathing under what you have now.
Strip the whole roof and have a commercial roofing company install a new EPDM membrane roof.

Aarone1972 01-31-2012 12:29 AM

Im curious why not. If a roof coating has been working for 40-50 years, why not keep using it? At least I assume it is just several coats of it over the years.

Windows on Wash 01-31-2012 06:25 AM


I appreciate your DIY spirit and ingenuity.

When you think about water and making something waterproof, it probably will serve you well to think of the Grand Canyon. That was made by water alone. Water is truly the universal solvent and in low slop application, it will find even the most infinitesimal gap/crack/seam and work its way to the lower sections and foster rot.

You might be able to band aid it for a year or two but you are back at square one at that point.

If you are planning on keeping the home for a while, I would urge you to invest in a new roof altogether and either use a TPO or EPDM roof, or build up the structure to create some additional pitch and use more traditional roofing shingles at that point.

You could also use a mechanical double locked standing seam.

shazapple 01-31-2012 01:23 PM

It sounds like it is an asphalt and felt roof. Asphalt/tar/whatever you want to call it cannot last without reinforcement (aka the felts, somewhat similar to tar paper used under shingles). Roofing tar is not the same stuff as the asphalt on your roof. It is not as elastic (stretchy) as the asphalt on your roof, so in a years time you will be back to square one, except the cracks will be bigger. The RV product may not be compatible with your existing roof, and won't last more than a couple years.

If you want to DIY you will have to tear off the existing roof and put down a self adhering membrane, similar to rolled roofing. Ask at your local construction stores. I strongly suggest you hire a roofer to put on a proper membrane like Modbit or EPDM.

RoofYourWorld 02-02-2012 03:22 PM

Can you post a few pictures of the roof?

Judging by the cracks and blisters, sounds to me like you have a small coaltar pitch roof. IF that is the case, you may have difficulty finding compatible coating materials. Additionally, you do not want to tear off this sort of system yourself as you can get some pretty serious burns!

A quick fix would be:
-Level the existing system out as much as possible (removing blisters, etc.)
-Fasten 1/2" high density recovery board (fiberboard or even good quality drywall) over the existing system. Make sure you know the depth so you don't over or under drill.
-Fully adhere a single-ply membrane on top.

Obviously there are several variables not mentioned, but that would be the quickest, least expensive, fix for what I'm understanding your situation to be.


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