Would a PBR panel roof be a good option for our newly bought 1980 built flat roof house?
The house was built by a commercial architect who used commercial supplies, the roof has a metal structure and is flat. It has had 2 elastomeric coatings applied the last one in 2015. The inspection revealed some pooling of water and a few minor bubbles. There has been no water leaking into the house. Two estimates to replace the 4,000 sq ft were $39,000 and $68,000. Another contractor asked if I had considered covering it with a metal roof (PBR) and I said I would look into it. After searching fruitlessly online I decided to ask if you could help illuminate the subject for me. I’ll try to attach a picture of the roof.
Thanks,
Pat Delacruz
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Replies
Pat, PBR roofing panels (also called rib-panel or agricultural-style roofing in my area) have to be installed on a slope, usually at least 1" in 12", but more is better. "Flat" roofs (technically called low-slope roofs) are usually closer to 1/4" in 12" slope.
Virtually every commercial building in the country has a low-slope roof with a membrane-style surface of some sort, so there's no reason that approach can't work. Why not just have the existing roof repaired by a qualified roofing contractor? If there is ponding and the roof structure is sufficient, the surface of the roof can be built up for better drainage. If the structure is not sufficient, that should be addressed first, by a structural engineer.
Thanks for the quick reply Michael. I was hoping for a less expensive option. I guess I just need to get more quotes until I get some that are closer than $28,000.
Pat,
I have never heard of the term "PBR panel roof," so I looked it up. Evidently the initials stand for "purlin bearing rib," so the phrase in its entirety is "purlin bearing rib panel." In Vermont, we usually call this "metal roofing" or "through-fastened metal roofing."
The reference to "purlin bearing" just means that you can install it on 2x4s that are installed perpendicular to the rafters, 24 inches on center. (You don't need plywood or OSB sheathing.) That's common on agricultural buildings.
Michael is right: that type of metal roofing is used for buildings with a sloped roof. You need membrane roofing. Any commercial roofing contractor (that is, a roofing contractor familiar with commercial buildings) should be able to give you a bid.
Pat, if you just have "some pooling of water and a few minor bubbles," I don't see why you need a full roof replacement if the membrane is just a few years old.
I don't know what 'elastomeric coating' means
could be some kind of rubber paint.
ponding is only an issue of 'why'. if it is because the structure is shifting that is 'bad' if it is because you cannot perfectly sculpture a roof deck, it is meaningless. Old built up roofing did not want to stay wet, but EPDM is used as a pond liner, so the only issue is seams. PVC I would think is the same.
To me the relevant questions are:
What is the actual roof, EPDM,PVC, BUR?
How deep is the ponding? less than half an inch?
Why is the ponding happening? Is the ceiling underneath showing signs of movement? If it is shallow and not related to building movement and not causing a leak, I don't think I could get excited about it.
Oh, and never speak to the roofer again who wanted to turn your house into a chicken coop
Thanks Keith,
I had also come to the conclusion that total replacement may not be warranted. I have 3rd roofer coming next week and I’ll ask all your questions, thanks again. I’ll post the results afterwards.
Roofers tend to answer in the affirmative when asked whether a roof should be replace, if only because there is a reason someone calls to ask if their roof is ok. I would always feel better if I was paying for a roof inspection rather than asking someone if they would like to do their job[replacing roofs in this instance]
I would suggest getting up their and asking questions and having them point out defects etc. if that is possible.
Please get on the roof and take a close up photo and post it. This almost looks like a TPO roof from the photo.
Agree with the others - you probably don't need a new roof. If this is indeed a 2015 applied TPO roof, if it was done properly you should have a 10-20 year mfg warranty for water bubbles. Also, the mfg may tell you that minor ponding up to 48 hours after a rain event is acceptable.
If you are bracing to spend $28k or more on the roof, first you need a roofing consultant, and a commercial NOT a residential one. What city are you in? Someone here may be able to recommend someone.
And also suggest you remove your phone number from your post...that is there for the entire internet to see and google's data crawler to find and could result in you getting many unwanted calls...
Thanks for the advice, but how is my phone number removed?
I just found out that it is a metal roof with tar and rocks originally then some kind of foam was added and then painted 2yrs ago with elastomeric for cash, no warranty. We live in Bay Co. Fl. I l’ll post pictures next week when I get on the roof.
Pat,
I have deleted your phone number.
Martin Holladay, GBA editor
Oh, tar and rocks is another matter... that's called a built-up roof, or BUR. In that case it is likely that you should replace the roofing. As CL said, get a commercial roofer to look at it--this is what they specialize in.
Pat,
It sounds like your built-up roof (commonly called a "tar-and-gravel" roof) was covered with spray polyurethane foam. The new spray polyurethane foam is the roofing; the coating simply protects the new roofing to make it last longer. Properly installed, spray polyurethane foam roofing is watertight and long-lasting.
For more information, see these two articles:
Roofing With Foam
Spraying Polyurethane Foam Over an Existing Roof