Flat Roof Over Garage – How to “Permanent” the roof
I have a 300 SF flat roof over the garage. It is pitched 1/4″ per foot as planned. The roof was built 5 years ago with torch down roofing material. Two years ago I rolled a layer of roof sealer – tar material – to seal off the nicks and dings from construction. Allied Materials guys tell me it was “the best” at $250 for a 5-gallon bucket. This year, I can see the alligatoring going on with that application.
Here’s the challenge. I am about to build a deck over this garage roof. I need to find a way to “maximize” the life of this roof before I place the deck on it (obviously I do not want to rip the deck up 5 years from now to do repairs to the roof, so I am prepared to overkill, if I have to, to protect the roof before the deck comes on.
In my research, it appears that liquid EPDM (rubber) is the thing to use. Though I can’t find anywhere where it claims what the life of this product would be. I can put a thick layer of this EPDM before the deck comes on, but wondering if there is an even stronger way to protect this roof? How about roll this on, then after it cures, lay out felt material (or any other rubber material) on top of that to give more mass and protection before the deck comes on. Am I helping to extend the life of the roof by doing so, or hurting it?
I just need to outlive the deck, which I hope is another 20 years to go. Thoughts?
Replies
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Rethink the material. For this application, an epdm roof would be my recommendation.
(I assume you mean the sheet goods, not the glop.)
yes
Had never heard of the glop, and rubber glop directly over asphalt sounds odd.
Seeking clarifications ...
I value your inputs but don't understand them. Are you saying go with the liquid EPDM and not put a layer of mass like felt or sheet rubber on there? What's your thinking here? What's the harm of putting on more material to protect the roof even more? Would the EPDM alone outlast the deck so I don't have to lift the deck up in the future to repair the roof?
sorry for the short not easy to understand reply..........
shaz has clarified it and his request from you is good.
More info on the existing to figure out your plan.
Personally, I would have originally put down a sheet type, epdm-properly flashing the railing posts and isolating the deck from the roof to allow water to drain. That assumes you had planned on the deck in advance. For now, I don't think a "rubber" coating is the answer-but have absolutely no experience with it. Done properly, I'm still a believer in sheet epdm for long lasting life.
I'm no roofer and would be asking those I trust for advice, but here's my thought. Divorce the asphalt based current roof with commercial insulation board prior to applying the sheet epdm-forget the coating.
A long time ago, a builtup roof w/smooth stone on top would last a heck of a long time. That art is old, though you still might find a commercial installer still qualified.
Is your existing roof actually torched down modbit or the self adhering or roll type roofing? Torch down modbit should still look new after 5 years, and should be water tight (assuming a competent installer) after 20. Roll roofing would be lucky to last 5 years.
I would stick with the sheet type membranes such as EPDM or modbit. They tend to last longer than liquid due to the built in reinforcements. As you've already seen, the liquid types are not meant for long term. Your idea of using liquid epdm over the existing would not work as the EPDM would not bond to the modbit or asphalt. The liquid asphalt probably failed so quickly because it is not compatible with modbit either. Unfortunately (and as is the case with a lot of these liquid coatings) you'll probably have to remove the modbit in order to put down a quality flat roof.
What is the construction of your deck? Would you consider putting down pavers or rubber mats instead of wood?
EPDM vs aspahlt
Just for clarification do NOT lay the EPDM right over the asphalt. The two materials are incompatable.