Flat roof advice needed, roofing old building becoming nightmare

17 Replies

I'm putting a new roof on a 1,150 gross sf ft brick 100 year old rowhouse. I've had 2 highly recommended roofers in and my head is exploding.  Roofer #1 only uses PVC, and tells me he'll wrap it over the low parapets and put a metal angle over the outer edge and wrap the PVC around the chimneys. He tells the pond due to settling joists he'd abate by using thick insulation that he tapers down, but that there still might be a puddle but it won't matter because PVC is so great. He's got promotional materials for PVC and everything, a slick act.

Roofer #2 is less slick, tells me PVC is newfangled and he only uses modified bitumen (which has like 2/3 or less the life of PVC, I have no plans to sell). Then he point out that the parapets are crumbling, that the current impermeable roofing materials and paint caused the mortar to rot. I pulled out my Leatherman and put the blade into the brick joint to the hilt with no resistance. Roofer #2 also does masonry and included $7000 to rip down several courses of brick along 2 46' parapets and rebuild them. His price of $10,500 to rip the old roof and put down new seems about right, and I don't think he's hustling me for the masonry.

Does anyone have a constructive opinion on this situation? Too often owning old property requires you to become an expert in every field.

I'm a roofer.   Ponding water is not a good thing even for a flat roof.  It can be corrected with tapered insulation or resloping the roof deck.  Most manufacturer's require a full drying of the roof within 48 hours.  PVC is used mostly on restaurants as it does well with oil that comes from hood exhausts, but it is a newer and developing product.  Its not the longest lasting membrane by any means.   I typically recommend Thermaplastic Polyolefin (TPO) membrane because of the strength of the seam welds and the solid track record of the product.       

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Roofer Two is more right it seems, I say this as a roofer also.  I would go with TPO as  Joseph has suggested.  If the Parapets are weak I would get that done.  FYI TPO is also a bit cheaper than PVC. Some say PVC is better than TPO.  However, both TPO and PVC are relative newer products.  

Tapered insulation to create at least 2 inch (4 would be great, but that means more budget) slope is almost mandatory.  If roofer one can put on tpo instead of pvc with a good deal.  However get the parapets done first by roofer two.  Also give roofer two the option to bid with tpo.  

If both can not do TPO (i doubt that), I would get a bid from someone who can.  

Thanks so much guys, I really didn't expect pro opinions here. Huh, some roofer threads I read were dubious of TPO. Funny you both think it's the best. Neither offered it, Roofer 2 seems to only do MB. This is a house worth well over $1m now (paid $250k 20 years ago) and scrimping a few grand on the roof is not what I want to do. But it's so hard with so many variables, last roof of similar size I got bids from $10k to $30k, and I had just paid only $300k for the place .  Dude wanted 1/10 the value to put a roof on it!! 

It's hard to really figure out these materials, the current roof I believe is EPDM even though roofer 2 said MB. It had a smooth finish. It's around 25 years old with very minor failure.  That's what I was told the PVC would do. But what really makes this a mess is Roofer 1 wanting to wrap the whole parapet, which is exactly what Roofer 2 said caused the mortar to rot, having no breathability because they tarred the inside and cap, and the exterior stucco was painted. So if I accept that, Roofer 1 is incompetent when it comes to dealing with masonry. What really sold me that #2 knew his stuff was when he pointed out that if I looked down the side of the building the parapet was actually curving in as the mortar collapsed.  I guess I wish #2 used better materials, but I don't want to ask him to work outside his comfort zone, that's how jobs get botched.

Another major difference is #1 wants to "maybe" get rid of the pond with tapered insulation, while #2 says he'll use 5/8 ply shimmed to get rid of it.

Finding roofers around here is very fraught. Our local board has a thread where every roofer that has a good reviews also has somebody slagging them.  Last roofer I hired, when i told him he'd get his final when it passed inspection told me "I should have expected as much from one of you people". Jews he meant. This was after he flooded the building by blocking the 4" cast iron center roof drain during demo and denied all responsibility.

I'm not a pro, but I've been learning the same stuff you are, trying to match roofing products, dealing with flat roofs....  Here's my take.  Roofer #1 might have the better product, and he might be proficient at installing it.... and he might have a newer way to handle the product, but roofer #2 sounds like he knows more about the industry as a whole.... Oh, and MB (which is what I've been using because I can install it myself... haven't burned down a house... yet).... after a few years, depending on the product can look just like EPDM.  I had the same thing, thought I had EPDM, but old smooth MB is what I had.

Here's what I would do.... take it or leave it.  Get a second quote, or maybe a third on the masonry, just to make sure your #2 is on the right track.  Ask him for a referral for a roofer that does good work with the membrane you want.... if he knows his stuff, he'll know who to refer you to.

@Johann Jells

PVC is a premium product and its been around quite awhile.  TPO is still fairly new and doesn't have a track record like the others yet.  Its made with similar chemicals as PVC but they claim its more flexible.  We don't use TPO due to short track record and poor installs when we have used it.  EPDM is a good choice as well.  A mod bit roof is not equal to pvc and is old school type of product.  PVC is slick to walk on.  Make sure they provide walkway pads around the roof.  PVC, TPO and EPDM are best taken up and over the parapet.  Roofer #2 called out the issue of the bricks because he has to leave them exposed with the mod bit roof at the wall flashing.  A Dens Deck can be used to over the parapet walls to give a uniform surface, basically plywood substraight but better.  Oh and Sarnafill(?), Firestone and Carlisle makes all the roofing membranes for other mfr and they relabel the product. I would stick with these 3 companies.  Based on your location I would go with a black colored roof due to more heating season than cooling season.  PVC comes in white, tan and gray.  Typically you see white.  I am becoming a fan of tan to help hide all the dirt on roofs.  You will always have minimal ponding of water on a flat roof due to installation issues with the insulation.  This means less than 1" deep of ponding water. If its more then it needs to be fixed.

Let me throw out another idea... A Retro-fit standing seam metal roof.  Same price range as pvc and 50 year life span.   Share some pictures.  What type of roof is on it now?   The brick sounds like it needs to be retuck pointed.  You should have a mason do this and not any roofer.

Tpo is the way to go.

Or slope your roof more

I was a successful housing rehab specialist for 26 years, now happily retired and taking care of my RE investments. Based on my experience, (and not knowing if your city or jurisdiction allows it) if I were you, I would completely tear out the roof and build a new, sloped roof, maybe 6:12, and design the rafters or trusses so that there can be room for an HVAC unit and maybe some storage space in the attic. It will serve you decades of relief! And increased house value! Of course, before you decide on a roof tear out, you should have the entire exterior and new roof blend in nicely for good aesthetics. Seek the services of a good Architect or home designer. Good luck! :)

Ideally Nanette is right.  Otherwise, go for TPO is what i would say.  PVC is a bit better than TPO, not sure it is worth double the price though. 

Slope is extremely important. 

Joann is right about the 3 roofing membrane manufacturing companies.

Thanks all.

@Sam LLoyd Getting a mason opinion is a great idea.

@Jim Adrian  Slipperyness is an interesting issue, there's just a gutter at the low end before a long fall, unless you hit the fire escape. I was leaning towards white, tenants pay their own heat/ac, and while being on the 4th fl of an old leaky building they're never cold, it can get brutally hot up there. I'm not sure you can repoint the entire width of the brick! Roofer 2's business is "roofing and masonry".

@Nanette Domitrowich That would be a fabulous way to destroy the value of my "brownstone" type building! Cheap infill with pink brick facades and peaked roofs are a visual plague in our historic neighborhood of flat roofs and ornate cornices.

@Johann Jells

PVC and mod bit are apples and oranges in comparison.  Would strongly vouch for PVC between the 2.  In my office, I typically detail PVC roofs and design them to go up and over the parapets with some type of metal coping.   I agree with points @Jim Adrian   mentioned regarding color, walking pads, etc.  The continuous surface just provides less chance of leakage.  Also, regarding warranty, you will have a bit of extra protection if you continue the roofing membrane over the parapet.  This is something you may want to confirm with the roofer.  Also, would recommend minimum 1/4" per foot tapered insulation.

@Milan Mehta Thanks. Can anyone comment on the issue of encapsulating the brick in this way? Roofer 2 seems to think it's real bad as it holds in moisture, but would moisture simply not get in with the PVC wrapover? For that matter why do MB roofers not do the wrapover? Too sharp an angle?

@Johann Jells  

To comment better on this we really need a picture to understand the problem.   Here is a link to the best practices way of flashing the parapet wall, detail 1.

Detail 1 https://www.carlislesyntec.com/view.aspx?mode=media&contentID=4546

Detail 2  https://www.carlislesyntec.com/view.aspx?mode=media&contentID=3620

As you can see in detail 2 it relies on a sealant joint to keep water out at the top of the termination bar.  Sealant last 8 to 10 years.  Where as detail 1, metal coping last +25 years.  Detail 2 requires 8" to 12" of wall height to make this detail work.  If you don't have this then this is not an option.  In detail 1 I would add 1/4" to 3/8" cover board to the wall to give a smooth  surface to adhered the member to.  Your additional cost is mainly in labor not material. The metal coping is reusable typically.  

@Johann Jells,

I have extensive experience with MB roofing on flat roofs in Chicagoland. IMHO it is imperative you rebuild the parapet walls before roofing. Tuckpointing only, will not be a solution that will last. Without seeing your roof, I can guess what has happened. You might not have noticed, but, I would be willing to bet that if you look closely at the parapet walls, you will notice that they have started to lean inwards toward the center of the roof. If you have clay coping tiles, they will be leaning inwards also. Some cheap contractors will try to sell you tuckpointing to fix this - it will fail within 5 years. To be properly repaired, the firewall (parapet) needs to be rebuilt down to the roofline so that it is plumb. The water from the coping tile should fall straight down to the sidewalk without landing back on the wall. Masonry walls need to breathe. That's why roofer 2 says not to wrap. The proper way to terminate a MB roof is with a termination bar wrapped with a counter-flashing. For more info regarding parapet and masonry walls I highly suggest heading over to buildingscience.com and check out what Joe Lstiburek and his colleagues have to say. Best of luck. 

@Jamie Moyer :

Thanks Jamie. I've put my head in the sand and done nothing on this, it's so confusing. So is there another way to roof this kind of building with PVC other than what Roofer 1 proposed? Cost is not an top issue, this is a long term hold for me. Or should I just get the best MB job I can, in addition to the parapet work. BTW, the roofer/mason only proposed stripping 2 courses, not the whole thing, and cost was $7k for the 2 46' sidewalls.

If you do go for MB, I recommend specifying 5mm white granulated. This is a little thicker than most (4mm) and the white granules will help protect from heat and U.V.. Hard to analyze best procedures without being there, or at least seeing a few photos. What are the freeze/thaw cycles like in your part of New Jersey?

@Johann Jells

Like @Jamie Moyer said, its hard to give advice without being there and seeing the wall and roof first hand.  If the wall is leaning or bowed then the wall must be replaced down to the roof line like Jamie mention.  He is giving sound advice. If bricks are white, then you have effloresces which confirms water is entering the wall.  The worst thing you can do is ignore the problem.  Water will destroy your building by causing decay and mold.  You don't want to get into mold mitigation as this will lead to asbestos and lead paint abatement $$$$$$ due to the age of the building.  Have an architect come out and look a the roof and give a recommendation.  Remember they are not selling products like roofers are.  PVC is your Cadillac product while modified bit is low grade chevy in my opinion.  There will be a noticeable price difference as well. Firestone and Carlisle make all the roofing products membranes for the other companies.  

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