2 Flat Roofs - 2 Situations - Same Fix?

We have 2 “historic” brick buildings with flat roofs in the central Midwest. They are next door to each other, but are different sizes. The larger is about 1,335 sq. ft. and the smaller around 875 sq. ft…

The larger building is our home, and had a new, conventional, “built-up” roof installed about 20 years ago. It’s been coated once or twice since then with a grey aluminized product that is now badly “alligatored”, with some linear cracks here and there. Recently, at infrequent intervals, there’s been a bit of leakage into a back stairway. Our attempted fix with a few tubes of roofing caulk has proven unsuccessful.

We actually have three problems: 1. A Leaking and deteriorating roof.
2. The cost of heating. 3. The cost of cooling.

When the roof was installed, we neglected to have the air space beneath insulated with fiberglass or cellulose. We’ve spent decades paying for that mistake, and won’t make it again. The weather here gets both very hot and very cold, and if the entire roof needs to be replaced, we’ll certainly blow insulation in there.

However, we’ve considered some modern roofing products that promise to insulate from above. They are ceramic/plastic coatings that reflect most heat during the summer and can help stem heat loss in the winter.
If we decide to re-mop the roof in conventional fashion, to seal out the water again, and then use the ceramic coating on top, would that be a sensible solution?

In other words, can we extend the useful life of this older roof with a combination of re-mopping and re-coating with “space-age” products, or should we start from scratch with an entirely new roof, insulate beneath, and then coat the new roof with the reflective coating?

The second, smaller building, is a simpler question. We bought it after the second foreclosure. It had been gypped, tripped, flipped, and sorely neglected. It took over a year to rehab it, including a brand new conventional roof. The roofers took off over 4 inches of old stuff, including what was probably the original, 1908, material. Fiberglass was blown underneath, so energy efficiency has been much improved. However, there is room for improvement. The makers of these ceramic roof coatings, in addition to claims of efficiency, also say that their products will extend the life of roofs by protecting from extreme temp. shifts and UV exposure.

Since this roof is quite new, not yet two years, it’s clean enough that an application of a coating would be fairly simple. Are the claims for these products substantial? Could they be a useful tool to save money on energy and future repairs?

Thanks for your time and attention.

Without knowing exactly which “space age” products you are talking about, I can only tell you that most coatings help strictly by increasing the roofs reflectivity and thus reduces the heat-gain and surface temperature of the roof system. With regard to your first building, it sounds like it is time to replace the roof. You will want to install insulation with the new roof system, and polyisocyanurate (iso) is the best way to go. After than, you can decide to go with either a conventional built-up roof or a modified bitumen roof system. My recommendation would be a two or three ply built-up membrane with a modified bitumen cap sheet, but then again I don’t know what your budget is for your new roof.

As for your second building, a coating won’t hurt you that is for sure. Although, that is assuming you either have a smooth-surfaced modified bitumen roof membrane or a smooth-surfaced built-up roof. I wouldn’t suggest applying a coating over a gravel surfaced roof, and most of your single-plys won’t need/accept the coatings, and there are some compatibility issues depending on the type of coating used.

Bottom line, come back at me/us with some more particulars about the roofs. Exactly what kind of roof do you currently have on your buildings, what type of coatings are you talking about having applied, i.e., brand names, etc…

The ceramic-filled acrylioc coatings have no real benefit over a plain acrylic. The ceramic is touted as heat-resistant, but they offer no better reflectivity than the plain versions.

Reflectivity is the only reason I would use the acrylic coatings. Some use it as a waterproofer, but the wwater permeance rating is so high that it will actually absorb water and lose cohesion, dissolving into the storm drains over time.

I would recommmend a white urethane single component roller grade for reflectivity on a rooftop. The two are comparable in cost. Urethane is mush better for roofing.

Insulation? Have you considered a Spray Polyurethane foam roof? it is the same insulation as the aforementioned ISO, same r value, but is the roofing system in itself. It is sprayed seamlessly in place and coated with a UV inhibiting coating. This system, if installed by a qualified foam mechanic, should last indefinitely if maintained properly also. Next time you re-roof (if on the proper maintenance schedule) you will most likely be looking at caulking repairs and another UV inhibiting coating. The longevity of the coating depends on what coating you use, and which spec is followed. Also, probably more cost effective than a conventional BUR.

Cerb, which incompatibilies with everest coatings and single plies?

We contacted our roofing company, an old-line family operation, and they pulled out the numbers.

The larger roof was installed in May of 1985. It’s a “Base & 3” 4-ply affair built of 43 lb. base and 2 layers of 15 lb. fiberglass paper with layers of tar in between. It was re-coated with aluminized asphalt in 1993, and again in 2000. ( The smaller roof was the same, but installed in August of 2003. )

This firm can also install a “rubberide” roofing system, which is evidently a form of “modified bitumen”. ( We’re unfamiliar with both terms. ) They told us that it had a white, granular surface, that would reflect some heat.
They also specifically warned against roofing systems that used sealed seams to create a larger membrane, indicating that those seams can fail.

“polyisocyanurate (iso)” is an unknown term, presumably a spray foam product. Is this the Soybean derived stuff? The last time we checked, there was only one company in town that does foam installation, and the estimated cost was 5X over fiberglass or cellulose.

We’re confused by the ending of the previous post:
"Cerb, which incompatibilies with everest coatings and single plies?"
Have no idea what this means.

We’ve never heard of a roof made of foam material … can it be walked-on? Can TV antennas be mounted on top, or are they left in place and foamed-over?

Here are the websites for the coating products we’ve researched so far.



The advanced age of the larger roof argues for a total replacement of some sort, either a conventional with a coating, or a more expensive modified bitumen with white granular top. The smaller one seems smooth enough to benefit from just a coating to reflect heat that may also prolong its’ usefull life.

We’ll try to get up there and take some pictures to post.

Excuse me if I seem too straight forward, but I am sifting through your post for respponses to your questions…

  1. Base and 3 is a 3 ply. Would be a 43 base, and 3 build plies of 15 and asphalt, not two. A base and two plies is a two ply.

  2. Polyisocyanurate is the normal board stock foam insulation used for roof insulation. Usually yellow foam with a grey facer. If your roofing company doesnt know what it is, fins another roofing company.

  3. Sealed seams…any roof that is not spray-applied in a 100% seamless fashion must have sealed seams, even modified bitumen. Different systems have different methods of sealing these seams, but they are all sealed, and it all comes down to the quality of the installer.

  4. SPF can, in fact, be walked on. You never want to install a TV antenna through your roof if there is another less destructive way to mount it. check out this link on foam roofing http://polythane.com/library/tamu.htm

  5. Yes, poictures would be best. You might not even need a total replacement if your mainteneance is up to par, like is sounds.

We went up on the roof and took some pictures.

The smaller, newer, roof is only mildly “alligatored” and seems a good candidate for some sort of coating … .

The large, old, twice re-coated roof has a much rougher complextion.

Unfortunately, there’s a glitch in our software.

We recently, and belatedly, went from OS-9 to OS-X.

Neither of the scanners, a Nikon & a Canon, have correct drivers.

So … for now there’s no way to post photos of these roofs.

We’ll try some alternate measures.

We’ll also try to re-formulate our question.

Thanks for your patience.

The DOE does not allow any coating product to have an insulating value (R-value) The only liquid applied material that would be suitable is as Aaron B said is (SPF) with a good quality coating on it (I personally use 100% acrylics) this will give you a energy efficient, sustainable, reflective fully adhered roofing system that will last you many years.

Where at are you in the Midwest?

We decided to get up off our butt and get some face-time with local roofing professionals. There are two roofing supply distributers nearby, so we walked in and asked questions.

The staff at both places were very helpful and informative. We learned what a “roofing square” was, saw a sample of ISO board, and brought home a piece of GenFlex TPO ( 45 ml. ) to show to our spouse. We also learned that modified bitumen was available in a smooth finish that would facilitate future coatings of protectant. Both suppliers emphasized that proper installation, sealing seams, was Very important, and that the hot-air gizmo that welds the sheets was quite expensive so that some contractors might use alternate methods of dubious value.

Both places also suggested that GAF acrylic topcoat was the way to go for the smaller roof. They were of the opinion that ceramic coating content, as found in other products, wasn’t worth the added expence.

One distributer had a sample of the latest thing in modified bitumen, a self-sticking product that doesn’t require welding of the seams. Has this product proven to be reliable, or is it still too new to tell?

We’ll do some phone work today and see if any local contractors install SPF spray foam roofing. That is an option we haven’t fully considered.

We’re located in the City of St. Louis, where old flat roofs and extremes of tempreture insure that roofers have a steady supply of customers. ( Since most of the housing stock is brick, and quite old, plumbers and tuck-pointers are also in demand. )

We’re going “on top” again this morning to get a more accurate measurement, and then we’ll make more calls and start getting bids for the various scenarios for the bigger, older, roof:

  1. Total tear-off and starting from scratch with either mod. bit or TPO with ISO board underneath and insullation blown in the space below.

  2. SPF foam over the whole thing, plus a coating.

  3. Putting ISO board over the existing BUR & topcoats, covering it with smooth white modified bitumen, and coating it when properly cured.

Thank you all for your time and attention.

We’ll continue to report on our progress.

( or lack thereof )

I am a SPF applicator out of Jefferson city, mo. I am going to be in the st. louis area in approximately 2-3 weeks repairing an old SPF roof that had some taper issues a nd didn’t drain well. If you are interested I could take a look at your roof when I am there. Just let me know. God Bless

I am a SPF applicator out of Jefferson city, mo. I am going to be in the st. louis area in approximately 2-3 weeks repairing an old SPF roof that had some taper issues a nd didn’t drain well. If you are interested I could take a look at your roof when I am there. Just let me know. God Bless

ive seen a hundred companies that are just like the first one you mentioned. First of all, one term you didn’t understand was the brand name “Ruberoid.” It is GAF’s version of torched down modified bitumen. I wouldn’t choose the first contractor because they sound like hustlers that do not keep up with modern times IMO. Theyre living off that third generation thing and failing to keep up with this generation.

If I were you with my knowledge of roofing and I simply didnt want to or couldnt do my own roof feasibly, I would go with the TPO guy if you can get some credentials. I’m not a big fan of ISO insulation because I’ve seen it delaminate (the gray seperate from the foam) and the weight of snow crush it far too often… UNLESS… you spend the extra money to put down some Densdeck, which looks like sheetrock, over the ISO. Everyone is selling ISO, including the union companies I’ve worked for, but I think it SUCKS! If it has that good of an r-value, put down the Densdeck over it with the TPO system is my take

P.S., why cant cellulose be drilled and blown into the space between the top floor and the roof and blown onto the ceiling of the top floor? Then you can vent from the sides with the holes you made to blow in the insulation? Then, you can use a few of those spinning vents on the TPO roof so the roof insulation doesn’t get soaked with humidity within the house. Same thing as a pitched roof except instead of a soffit you drill through the freezeboards and slap the vent over the hole. If the house or building is brick, this might not be the way to go, but if the building is made of wood this is the way to go I think. Hehe, edit. They are brick I just reread :smiley: Still is there a hatch in the building that leads to that crawl space? I did cellulose insulation for a few months and had to climb in many of those crawl spaces. It sucks, but thats how we insulate here in New England.

Well, SPF can be twice the R per inch…This will pay you back.

Thanks again to everyone for the feedback.

We made some further inquiries about the effects of local weather patterns on different roofing materials. The general consensus was that because of the extreme variations in temp., combined with high humidity, a foam roof could be problematic. Keeping a level surface with expanding foam can be tricky, and removing it once in place could be a major headache. ( Or so we’ve been told. ) Although we can, and do, get substantial snowfall here, it never builds up enough to threatens the roof.

If we wanted to drill holes in the roof and blow in insulation, we would have done it decades ago. Too much risk of leaks, combined with no way to verify coverage in the airspaces. The local guys would have had to cut through the whole roof, open up a trench, cut the roof, blow it in, and hope the refilled trench didn’t leak. No thanks.

There’s isn’t any crawlspace per se. Both of the long axis walls have four metal grates set in the brick that vent the airspace between the ceiling and the roof. At the front of the building, the high end of the slope, there’s about 15-16 inches of space that tapers down to about 8 inches at the rear. This is a very common feature in older homes here. ( St. Louis is awash in brick buildings built from the 1880’s to the 1930’s. )

The only way to properly access the space is when the roof is off and portions of the wooden sheathing have been removed. We’ll have to do some up-to-date research on the “fiberglass vs. treated cellulose” question, but we’re fairly certain that foam insullation just isn’t in the budget.

We’ll contimue to update the job as it progresses … if it does. ; )

Just when we thought we had a handle on the situation, along comes a presumably informed second opinion.

We’d asked two friends in the Real Estate business to suggest a roofer, and he just came by and surveyed both roofs. This guy has been tuckpointing and roofing here since he was 12 years old, and should have a good handle on what works and what doesn’t.

The first suprise was that he thought that adding fiberglass or cellulose insulation wouldn’t be cost effective, or particularly usefull. ( He’d done it in his own house and didn’t see much change in his energy bills. ) This seems counterintuitive but, evidently, these houses were designed to have air circulating between the roof and the ceiling. Putting a layer of ISO board on top was also discouraged in this case.

He suggested not tearing off the old existing roof, but covering it with either another BUR or a modified bitumen product. Evidently, this building could have another two roofs added, plus coatings, before weight became a concern. The smaller roof, in his opinion, only needs a hot-mop coating.
He takes a dim view of the white acrylic coatings that are available, suggesting that they could actualy cause faster breakdown of the underlying layers, and wouldn’t appreciably lower utility bills either.

So … we’re almost back where we started. Since we have no utility bills with which to make a before and after comparison of the fiberglass blown into the smaller house, we’re justifiably confused.

Any comments or further suggestions are, of course, most welcome.


Personally, I think you are wise NOT to consider putting SPF over your existing roofs. And yes, once you have committed to SPF you are committed long-term due to the expense of removing the SPF from every surface it was sprayed on.

Once again, you may want to look into what I suggested previously, i.e., a 2-3 ply BUR and a modified bitumen cap sheet installed over polyisocyanurate and perlite/wood-fiber roof board insulations. As for S&G’s comments about the facer delaminating, that was a problem at one time with thicknesses of 3-inches or more, which is why you want to generally use 1.5-2.0 thick insulation. If you need greater R-value, you use two layers of polyisocyanurate. It is a great insulation, and is probably the most commonly used insulation in low-sloped roofing today. There are other options like foam-glass (expensive), fiberglass (low R-value), perlite (low R-value and turns to mush when wet), etc., so I still have to go with the Iso. Now, as for the recommendation of installing Densdeck over top the iso, that is not a bad recommendation and I often specify it on jobs where I know expense isn’t a big issue; however, if you are operating on a tight budget it would just be an added expense. It isn’t a bad idea, but you would have to weight the extra expense against the added value.

Just read your post about the guy who had been roofing and tuckpointing since he was 12. All I can say is, I don’t like his recommendations of adding more plies to a roof that is failing. The new plies will only be as good as the substrate you attach to; kind of like painting over cracked and peeled paint, if you will. I run into people all the time that tell me “they’ve been roofing for over 40 years, and have been doing it this way the whole time.” My response to some is “well, you’ve been doing it wrong then for the last 40 years.” Point being, just because somebody’s been doing something for a long time, doesn’t mean they are necessarily good at what they do. I spend a lot of my time surveying older roofs, something a lot of roofers don’t do, and I see the problems that develop over time. Hey, back when I was roofing I used to put down roofs and would never see them again. I’ve spoken to my old bosses and I know those roofs have performed well, but I’ve not gone back to look at them. So as with most roofers, unless their roofers are leaking and they go back on leak calls, they don’t get to see their work several years later.

Do what you want, but if you are that confused, I would suggest you contact a roofing consultant.

Did you know that polyisocyanutrate insulation is exactly the same as SPF? In chemical compostion?

To elaborate further on cerberus’s post, regarding being in for the long term with SPF, THAT IS EXACTLY WHY IT IS SO SUCCESSFUL when properly prepared and applied. It is a long term product that will require maintenance coatings instead of re-roofs down the line when performed on schedule.

You see, those that do not know SPF talk it down, because they do not understand the chemistry, the application, and the limitations iof the system. Like any system (even the viable alternatives that cerb mentioned) it has to be properl;y applied and maintained or else you will experience failure.

I know for a fact that when your initial warranty is up, and you have reaped all the benefits, your foam roof warranty can be renewed for up to 15 years if the UV barrier has been maintained and another fresh coating is applied per GE specifications. Yes, the GE (now owned by Bayer Corporation) foam roofing system is widely used and functioning perfectly on millions of square feet of commercial low slope applications.

Ever heard of Texa A&M University? They did all of their low slopes in SPF, and have had all successful applications, and the roofs have paid themselves back on average of less than 7 years in energy savings and lack of need of replacement. Check out this link http://www.polythane.com/library/index.htm
and this one
and this one http://www.polythane.com/

You see…when most contractors are called out to inspect failing SPF roofs, they know absolutely NOTHING about the system, know absolutely NOTHING about how to repair the system, know absolutely NOTHING about the root cause of failure. This is why they recommend a lesser grade, more costly "Conventiona"l roofing system that they DO know about. If you dont know it, you cannot possibly know how to fix it.

Check out this link http://rsimag.com/rsi/article/articleDetail.jsp?id=158084

Even the roof consultants institute recognizes the system and its root cause of failure.

If you have anymore questions regarding the use of Spray Polyurethane Foam roofing systems, I can point you in the right direction.

BTW, I do not see the benefits of it in your situation, since you have what is known as a cold roof assembly, whereas the building envelope insulation is not part of the roofing assembly itself. A nice BUR would serve you better, if your tear off the existing.

Aaron, you went through all of that just to agree with me in the end? No, I don’t mean agree with me about SPF in general, but agree with me about installing a BUR system. Why didn’t you just say you agreed with me to begin with, rather than taking the round-about way of agreeing? And yes, I’m not a big fan of SPF, but I actually do deal with it at work and have watched it installed. I’ve been involved with an SPF being scarfed down, and an new layer applied overtop an existing. And as a roofer, I’ve also had to remove an SPF system from a concrete roof deck with a Rhino, scrappers and utility knives. I agree it is great for insulating purposes, but I don’t like it as a stand-along roof system and think it is better suited for application over existing BUR as a “coating.”

I realize that you are an SPF applicator, but you don’t need to get all up in arms when someone doesn’t promote your product.

[quote=“Cerberus”]Aaron, you went through all of that just to agree with me in the end? No, I don’t mean agree with me about SPF in general, but agree with me about installing a BUR system. Why didn’t you just say you agreed with me to begin with, rather than taking the round-about way of agreeing? And yes, I’m not a big fan of SPF, but I actually do deal with it at work and have watched it installed. I’ve been involved with an SPF being scarfed down, and an new layer applied overtop an existing. And as a roofer, I’ve also had to remove an SPF system from a concrete roof deck with a Rhino, scrappers and utility knives. I agree it is great for insulating purposes, but I don’t like it as a stand-along roof system and think it is better suited for application over existing BUR as a “coating.”

I realize that you are an SPF applicator, but you don’t need to get all up in arms when someone doesn’t promote your product.[/quote]

Well, FYI, I do not install SPF solely. Check out my new site located in my signature line, I install BUR, mod bit, EPDM, shingles, metal, etc.

I am, however, firmly against the spreading of negative information on viable roofing systems, if properly applied. That is why I offer the information and the links.

As you know, especially, I do not have a problem telling somebody when I think their info is not up to par, so there is no reson to go the round about way to agree.

What issues do you have with SPF as a stand alone?