Flat Coastal Roof Questions


#1

Hi all,
I have been lurking for several weeks and have learned a great deal from your informative posts.

I am looking for any advice you can give based on the house we have.

We recently purchased a flat roofed fixer upper on the Alabama coast. The house is located on the interior of a barrier island.

The house constructed of concrete block, with concrete interior walls.

The roof deck is a flat concrete slab roof with a little slope. The roofing is built-up tar and paper that appears to date to the original construction in the 1960’s. The metal flashing is literally crumbling and the roof is lifting in several areas. There are several leaks. Keep in mind that since the house is all concrete the leaks do little, if any damage and there is no wood to rot.

I plan to replace the roof myself (I am an avid diy’er having helped build several homes, built numerous pieces of furniture and a boat.).

I originally considered EPDM, but have learned it will not handle the climate based on posts I have read. Modified bitumen roll roofing appears to be the best choice for doing it myself.

I am planning to use one of the systems such as GAF’s Liberty Peel & Stick 3 ply system or GAF’s Tri-ply using cold adhesive over OSB.

  1. Would you recommend peel & stick or cold rolled? Any specific brand or system you prefer?

  2. Can I attach the OSB to the concrete deck using adhesive? If so, what do you recommend? Otherwise, how should I fasten it?

  3. The house is humid and subject to sweating, because all of the walls and roof are concrete. Do you advise any type of barrier between the OSB and the concrete deck or between the OSB and the roofing?

  4. Can you offer any links or advice on installing the flashing & drip edge? The best info I have found so far is on Certainteed’s website.

Thanks for any help you can offer!


#2

Wow!

First of all, the leaking roof could very well be causing you problems with the concrete that you can not see. If there are any cracks in the concrete deck, and that includes crazing, then entrapped moisture can penetrate the concrete and cause the steel reinforcement to rust. Assuming the deck is reinforced with rebar, as the rebar rusts it expands and can cause the concrete to spall. Anyway, moving right along to your other questions…

  1. You can replace it yourself. - I wouldn’t recommend you doing that, but try it if you like.

  2. Peel & Stick is your choice. - I would suggest you look into cold adhesives instead. Derbigum makes a nice product, but seeing how you are not a contractor you will have trouble getting your hands on the better roofing materials.

  3. OSB board on roof. - Why would you want to do such a thing? You can prime your concrete roof deck and install a modified bitumen with cold adhesive straight to the roof deck, though I suggest you use a system that has torch-fused laps.

  4. Vapor barrier between the OSB and roof deck. - Once again, if you don’t install OSB board the roof membrane will be the vapor barrier. However, if you install insulation on the roof, you may have to have someone runs some calculations to ensure you are not creating a system that will accumulate condensation within the roof sandwich. Once again, I would not recommend you do this yourself.

  5. Flashing and drip edge. - SMACNA and NRCA are the two places you want to start with regard to looking for standard details. Of course, the various membrane manufacturers also have details for their systems.

In addition to checking out Performance Roof Systems (Derbigum), you may also want to check out Soprema since insulation and/or Sopraboard can be adhered with their HVIA-III adhesive. Of course, you could also use Insta-Stik.

One last time. My advice to you is to not try this yourself. The roof is one of the three most important components to a building, and it is what protects your contents from water damage. Do yourself a favor, and hire a professional.


#3

goto www.hydro-stop.com and contact support. They will train you to put on thier roof on the job and then warranty it. the system is perfect for your situation. It will adhere straight to your existing concrete deck. No flashing req’d


#4

i live in mobile alabama not far at all from dauphin island i am assuming this is where you live you can email me and i will look at it and tell you what you need email coulson.roofing@hotmail.com don’t forget the period between coulson and roofing


#5

beutifull everyone,
except the part were cerberus scares h/o , on the concreate deck
assumtions.

once again nothin left for me.

gweedo


#6

what happens to epdm in your climatic area?i have a 3500 sq ft shop in phoenix that has had epdm on it for over 12 yrs,it sees deck temps of 160 degrees F.no problems yet.


#7

Thanks for the info!

I’m aware of the consequences of water getting inside the concrete. The house is overbuilt like a bomb shelter…the roof deck could be weakened considerably and you could still park a truck on it.

Based on what I’ve read in this forum, a number of EPDM roofs in Florida do not seem to have faired well in the tropical climate due to shrinkage… I actually like the idea of EPDM better because of the easy repair…but modified bitumen seems to be a better choice based on other flat roof posts I have read.

I’m looking for any input on a flat roof that an experienced DIYer can install that should last at least 10 years, and preferrably longer in a hot climate with the occasion hurricane.

I respect you guys and I know a professional could do a more efficient job…but I like doing things myself…I change my own timing belts, replace my own suspension, rebuild my own two-stroke carbs, replace my own waterline, upgrade the wiring in my house to meet code, build my own 24ft boat to fish in the gulf…


#8

Waiting to see how this one ends up… I’m thinking peel & stick CertainTeed FlintLastic 3 Ply with an added secure vapor barrier below all of this.

Question: What kind of penetrations do you have (if any) going into the roof deck?


#9

Let’s see if I can describe the layout of the roof…

The house is layed-out in a “U” shape, with the chimney at the lower right corner of the “U”. No other pentrations…but the inside if the “U” is a screened porch with an elevated roof that slopes toward the back of the house.

The highest part of the elevated roof butts against the chimney. Water is leaking into the porch area because the plywood on the side of the raised roof is separating from the poor attempt at flashing…that only extended a couple inches up the wall. This is the only part of the house that contains any wood. I plan to replace the separating plywood with fiberglassed marine-grade plywood and to replace any other soft areas of the raised roof…and to run the new flashing extend 8-12 inches upward.

Thanks for the help!!


#10

Hmmmmmm… sounds like a job for CAPTAIN PHOTOGRAPH!

Seriously, though… other than for your mod into fiberglass, a picture or two would really assist (well, me anyhow).


#11

Hard to give sound advice without seeing the job in detail but from what you’ve said I would look into ballasted EPDM over insulation board. (professional installation)

Liberty Peel and Stick (self installation)

I’m not a huge peel and stick fan but I know you need to prime the substrate prior to application. I’ve only put it down on wood decking and can’t offer any advice on concrete.

They make plenty of concrete fasteners, including but not limited to:

Screws
Spiral or Fluted nails
Zamac

IMO Zamac is the best but not practical for every situation.

Yes, water can tear up a concrete deck, lol. Good luck.


#12

[quote=“Tar Monkey”]Hard to give sound advice without seeing the job in detail but from what you’ve said I would look into ballasted EPDM over insulation board. (professional installation)

Liberty Peel and Stick (self installation)

I’m not a huge peel and stick fan but I know you need to prime the substrate prior to application. I’ve only put it down on wood decking and can’t offer any advice on concrete.

They make plenty of concrete fasteners, including but not limited to:

Screws
Spiral or Fluted nails
Zamac

IMO Zamac is the best but not practical for every situation.

Yes, water can tear up a concrete deck, lol. Good luck.[/quote]

Sorry Tar Monkey, but that is the last thing I would recommend for him to do on his house. Not only will the ballast become deadly projectiles during hurricanes, but it may also be illegal like it is here in Houston. After Hurricane Allison (I believe that was the one) hit Houston several years ago, it is now illegal to use ballasted roofs in downtown Houston.

As for the homeowner, there is one possibility you may want to consider. I don’t even like mentioning this, and it is not my recommendation, but in theory it should work and it would be an easy DIY job. There is a product that used to be called Vulkem 201, but since Mameco was bought out by Tremco I believe it is now this product:

tremcosealants.com/commercia … asp?id=245

Anyway, it should come in two grades, self-leveling and vertical applications. You need only prime the concrete roof deck, then squeegee apply the membrane out of 5 gallon buckets. You can even do a double application if you so desire. The one catch is you need to cover the membrane with an asphaltic coverboard and something like concrete pavers. It would be hard work, but you wouldn’t need much else but a squeegee, trowel, ladder, and a way to get materials on the roof. If you want more information, just ask me and I will see what I can do.


#13

If you would like a roofing system that can fully pay you back, look into a professional SPF roof with a polyurea membrane applied for long-term saltair protection. The first thing to fail in these situation (given that the SPF roof itself was properly installed and maintained) would be the metal perimeter flashings, but these, too can be covered with a polyurea membrane for salt air protection over the long-term. :slight_smile:


#14

He has clearly stated he wants to do it himself, so I don’t think buying or renting all the equipment to do an SPF is logical for him. Not to mention, as a first time applicator he would certainly screw it up. That is why I mentioned the Vulkem 201, because how hard is it to pour a roof out of a bucket? Then again, he may also want to look into HydroStop.


#15

Yeah, just throwing out options if he might be interested in system payback. :slight_smile:


#16

Yeah, just throwing out options if he might be interested in system payback. :slight_smile:


#17

Thanks for all the input.

I’ve decided to go with a cold-app app modified bitumen with fuseable seams.

Now, I have to find a source in Mobile Alabama that stocks one and will sell to a home-owner. I will be calling around in Mobile this week.

Any suggestions as far as a product or source?


#18

Have you ever torched modified bitumen seams together before? If not, do you really want to learn on your own house? Once again, if you seriously want to do it yourself I would look into something like Vulkem or Hydrostop. This would allow you to seal the concrete roof deck, and you wouldn’t be playing with a torch on your roof. Also, as you will find, the better modified bitumen products will be hard for you to acquire. Instead, you will have to settle for low-end products that don’t need to be installed by manufacturer approved applicators.

Good Luck!!


#19

If youre going to have the torch blaring away, why have the cold process?


#20

Good point Aaron. If I remember correctly, it is a concrete roof deck, so it isn’t like he is going to burn his house down. Still, since he isn’t a roofer I think it is best he look into a “roof in a bucket” product if he is going to do it himself.