OT Flat roof systems... Coments?

Well, it's time to bite the bullet and get the oldest part of our building re-roofed. 1800 sq, feet, wood deck, 130 feet of brick parapet wall, and about a half dozen penetrations for vent stacks and the like. The current coating is the common asphalt built up roof, covered with gavel, and is at least 25 years old.

I'm not real familiar with flat roof systems, but was always under the impression that on a built up roof, they just swept the gravel to one side, added more layers of hot "tar" and paper, then redistributed the gravel. However, none of the roofers quoting the job want to do this; each wants to quote a membrane system, and I am totally unfamiliar with the pros and cons of each system, so I'm asking for any experiences, good or bad. Here are the three that have been quoted so far, in descending order of cost:

EPDM Rubber The "rubber roof." I understand this material has been in use for quite a number of years, and the sheet itself seems to last a long time. Most of the failures I see discussed on the web seem to be with the adhesive used in seaming.

APP Modified Bitumen The "torch-down" roof. Most failures seem to be related to torch technique during seaming.

TPO Thermoplastic polyolefin It's new. It's white. It's cheap, about 2/3 the money of the EPDM. It also doesn't have a very long track record.

Comments?

Dennis

Just finished getting a new torch down system installed. Looked at all 3 types and chose the torch down for price vs. extreme heavy duty build up / quality of torch down and its resistance to hail. Basically you are correct it is all in the proper procedure when installing.

Torch down properly done is a good system Mine has lasted well for 15 yrs. One thing to insist on is an overnight fire watch after this is done. I was supposed to have one. But, at about 3 AM the watchman decided it was no longer needed (got tired) and went home. Got the call at 4:30 AM that the roof was on fire. Our excellent fire department knocked it down with minimal damage---mostly smoke. Darn near lsot the whole works. Thanks to a neighbor who saw the problem and called it in disaster was avoided.

The torching to seal the roof exposes wood to intense heat. It can catch and smolder for hours before is really gets going......

Denis.

No direct experience but an old retired stationary engineer told me that the secret was to use pitch and not tar. Pitch has fibers in the mix that prevent tears. The tears are where the leaks form. Of course trying to find contractors that use pitch today may be the biggest challenge.

I really prefer the TPO.

The EPDM adhesive issues are real. Not huge but as the EPDM reaches end of life it will start to shrink from oxidation and start stressing the seams. Eventually this causes the seams to separate. The glue for the EPDM is also incredibally expensive. The EPDM is also hot in the summer. A portion of our old roof had been done with EPDM. It was a system that had attachment nails about every 15ft. Each attachment point had a 12in.X12 EPDM cap that was glued to the membrane. Needless to say, every point was a potential leak. The system was only on the market for a couple of years before the manufacturer withdrew it from the market because of warranty claims.

The white TPO will significantly reduce your building interior temperature in the summer. I just did 125,000 sq. ft. at work several yrs. ago. The building was right at 100yrs. old when we did the roof. The TPO does not require tear off which is where the huge cost savings come from.

One big issue with the built up roof system is the weight. That is why none of your roofing contractors wanted to top coat the roof.
Good for them. The old roof is also getting expensive to landfill. If it is a pitch roof, then the dust really burns your skin if your sweating. This is why the roofing crews don't like pitch. The hot roofs are also more susceptible to cracking or seam separation from building movement, especially the roof deck boards than the TPO or EPDM.

The TPO roof also has no solvent weld or adhesive joints. The TPO is thermal welded so there are no seams when complete. Also membrane damage repairs or roof modifications can be made with just a heat gun to weld the TPO. The membrane welding temperature is also relatively low so there is a greatly reduced risk of fire. The TPO systems have been holding up if they are applied correctly so I wouldn't be too concerned with the short time that they have been around.

When we were talking about a new roof, I discussed this material debate with several roofing contractors that I had known from previous projects and that I trusted. They all said the same thing, go with the TPO. We did and the cost savings allowed us to put some money into badly needed insulation and still get the whole project done.

A final comment, whatever system you choose, just be sure that you are comfortable with the roofing contractor and trust them. The best warranty in the world is no better than the contractor that is standing by his work.

good luck with your decision

Make sure that what ever goes on top the roof has good crickets and grading.
Bird baths kill roofs.

We have a torch down that is holding up well. One suggestion along your parapet wall is don't let the roofer use the membrane for any drain penetrations thru the wall- pay the extra to have metal scuppers made up with large flanges up the wall and out on to the roof surface. Also have a metal cap over the top of your wall so you don't have sealing issues on the top of that wall that will require maintenance.

What about PVC? the seems are welded and they last a long time 20-30 years around here.

Jeff

My new tar/gravel flat roof failed after only 6 years, and, of course by then the roofer was out of business and out of town. So, armed with a serious dose of mistrust, I decided to do the job myself. Ended up with a modified coal tar rolled membrane system called "Jiffy Seal." Don't know why it was recommended as roofing - I understand it's usually applied in below grade situations as a waterproof barrier.

After a few years it was looking a bit eaten up by UV, so I slopped on some of the "Snow Roof" elastomeric coating from the local home improvement store. Since then, I've maintained the roof with more of the coating about every five years, and the roof is still sound, solid and leak-free. Oh, and cool because it's white.

At this point, 34 years and counting - not bad for DIY.

1800 sq. ft.! 30x60 or any combination thereof. If I owned the building and was planning to be there for many years I would go with a truss and metal roof over the existing roof. Yes, leave the old one on and put an "A" roof on. Cooler in summer and forget about it for your and your kidds lifetime. It is worth the investment. After rereading your original post this is only a partial repair so maybe a new roof system is not for you.

We did TPO 2 years ago. We tore off the original roof, added a layer of foam insulation (1" if IIRC) along with correction of a few crickets as Miguels noted.

We couldn't be happier. Summers are an easy ten degrees or more cooler inside the building and winters are warmer. The membrane goes all the way up the parapets and over the edges and covered with the original caps around the perimeter. Our roof is about 20,000 square feet and cost was around $60k all in and it took about a week to do. No leaks so far after two extremely rainy seasons and at least a foot of snow and ice over one winter.

Motion, did you pay for an extra extended warranty from the manufacturer, and if so, what were the terms? Complete replacement for the life of the warranty, or monetary settlement prorated over the term?

Dennis

Wassa cricket?

Thanks for the comments so far.

I had given some brief thought to re-coating the existing, but there are two problems: the need to sweep and remove 5-6 cubic yards of gravel before I can even see the existing built up roof, and the fact that the roofing paper is sagging and pulling away from the parapet walls.. I've been chasing split seams on the parapet walls for a couple years, and it's not going to get any better.

The existing roof is a single pitch enclosed on three sides by brick parapet walls. The fourth side originally drained into a gutter; is now flashed down onto the metal roof of an addition. There are no through wall scuppers., and the existing roof is straight enough that there are no pools.

All three contractors priced less tear-off; there is only one layer of roof at the moment, it must have been stripped last time. Of course, they still have to remove the gravel, and strip the parapet walls. They will install a layer of some sort of rigid insulation board to lay the new membrane on; this will still weigh less than the gravel they remove.

I haven't asked about PVC because no one bid that material.

Keep the comments coming.

Dennis

A cricket is a small built up, sloped or gusseted area, usually in a corner or behind a chimney. It's used to divert rain water from places where it might otherwise collect due to gravity and runoff...basically they are used to keep water from getting trapped in corners etc.

There are always some site specific considerations that can dictate why one flat roof system might be more suited than another. Local climate, season of installation, qualified contractors with experience in the system you want to use, size of job etc. Weighing all these factors, then picking the best system and contractor is the best recipe for success imo. The ideal roof on one building in the midwest might be completely different from the ideal roof on the coast in Florida, or in a wet and shady location vs full sun.

I've been roofing for over 30 years, started out hot roofing and installing BUR (Built up roofing) hot roofs with slag like what you have now. Pretty much done it all, hot roofing, pitch work, epdm and torch down, elastomeric rubber coating roofs...a little hypalon poly membrane, specialized in flat and standing seam copper, stainless and tin etc. (Never did do the old canvas roofing with the lead paint tho ...) Worked on giant jobs like some of the ones mentioned above and tiny little residential porch roofs too. Segued into sheet metal roofing and custom ornamental work about 20 some years ago, but still get my hands dirty with asphalt every now and then.

I did a job similar to yours in October 2012 and I used the Certainteed Flintlastic. It was a smaller job, only about 500 sq ft, but was a tear off of 5 roofs on top of one another with some penetrations and unique flashing considerations. Very pleased with the product and easy application, and it has been doing a great job as I check it out every 6 months or so for regular maintenance...long time customers. Here's the info... If you do use this product try to install when it's right around 70-80 degrees, and low humidity for best results and easiest application. Hire an outfit that is qualified and has a good sized crew, and can knock your work out quick, that's a big key to success with a SA (Self Adhering) single ply system. Check references and previous customers! The integrity of your contractor is paramount in getting a quality job that is going to last, regardless of the system you use

http://www.certainteed.com/products/...mercial/308479

I like the Flintlastic because there is no fire risk like torch down, it's clean and easy to maintain, and the single ply modified bitumen membrane systems have been around long enough where they are relatively well proven in the field. They also offer some energy efficient reflective surfaces that you might want to look into...maybe even get some tax credits. It's a fairly simple system so there's not as much technical expertise required from the contractor, you job isn't too big and can be installed in a couple days. This is the perfect time of year for a self adhering single ply system too. Self adhereing membrane technology has been around in different forms for many years now and I like what I've seen from the very beginning. All fwiw

Check your load requirements on your existing joist system, but chances are good you can just sweep the slag and prep your walls as proposed, lay as little or as much insulation as your budget allows, and re-roof.

Some good comments above. Personally after so many years in the trade, I'm always somewhat leery about the newest, latest, and "greatest" new products that are developed and released. The thermoplastics and PVC membranes have been around for a while, but if you choose one I think it would be worth it to research the brand and avoid something that doesn't have a long track record. Welded seams require qualified mechanics and more technique too. I don't care how much lab testing is done, anything that hasn't been proven in the field is suspect IMO. I've seen catastrophic million/billion dollar failures in this industry over the years with some of the newfangled BS that they put out. There is no substitute for field tested materials and methods that are proven to work over many years time, and in many different climates.

Modelman said:

APP Modified Bitumen The "torch-down" roof. Most failures seem to be related to torch technique during seaming.

Click to expand...

When our torch-down blew off last fall, it came loose as one giant sheet. The mechanical fasteners were the failure.