Built Up Roof (BUR) vs Modified Bitumen Roof (Torch Down)

I need some advice and/or opinions about these types of roofs. I have a flat section of roof on my house that needs to redone. I had this roof completely torn off and redone (BUR) approx 11 years ago. I spent a whole lot of money with a LICENSED contractor on this roof wanting not to have to deal with it again for a long time. Apparently it wasn’t done correctly according to the roofers that have come out and bid the job. I was told that they didn’t prime the edge metal correctly and this caused the edge to lift up/de-lam and water to wick in. It has destroyed all of the fascia on this part of the roof and some of the sheathing underneath. Other than the edges lifting up/ de-laming, the roof is still in relatively good shape. This is a FLAT roof with less than 1/4" per foot fall. Some of the guys bidding have suggested modified bitumen (torch down) as the way to go and some say that the BUR is the way to go. Which would provide me with the better roof? Which would last longer? Is it better to go with a 4ply (base, 2 11 lb. plys, granulated cap sheet) or a 5ply (base,3 11 lb. plys, granulated cap sheet)BUR? What about a 2 ply modified bitumen vs. a 3ply modified bitumen? I live So Cal. and we don’t get a ton of rain. I would like this roof to last at least 10-15 year min. Thanks in advance for any advice or suggestions!

I looked a roof in Santa Fe Springs not too long ago. Assuming you live somewhere in that vicinity and have similar climate, your biggest battle will be with fighting solar radiation.

Here are my questions:

What type of roof deck, i.e., plywood, OSB, plank, etc.

Any insulation above the roof deck, or is roof installed directly over the deck?

Exposed ceilings inside?

Where in SoCal are you located?

Now some answers:

A 4-ply is better than a 3-ply, but a 5-ply is better than a 4-ply. Me, I’d install insulation, a base sheet, 2 or 3 plies of felt, and then a white granule surfaced APP (not SBS) modified bitumen roof membrane.

You may also want to consider hiring a consultant to do a final inspection at the very least, but I warn you it won’t be cheap; though it may be your best protection against an improperly installed roof. You see, plumbers and electrician have city inspectors that come around and make sure the job is done right. That is NOT the case with roofing, where you just hope you selected a competent roofer.

The roof deck is plywood. The roof is installed on top of the deck. No insulation on top of the roof deck. No open ceiling. Insulated ceiling below roof deck. I live in the South Bay, close to LAX (10mi.). The roof currently is a 5ply BUR (base, 3 11 lb. plies, white granulated cap sheet). What is the difference between APP and SBS? I’m not above spending the money, but don’t want to spend a ton of money and not get a roof that will last. DON’T want to do this again anytime soon! LOL Oh, one last thing, the roofer that did my roof finally came out and looked at it and said it was MY fault because I didn’t do any maintenance!! I did pull permits and never got a final. Roofer said “why do I need inspection”?? I’m not a roofer, but apparently I might be a better one that him!! LOL LOL

Ok, RacerX, I don’t know you personally, so please do not take my following statements personally. I am going to vent on this subject for a second and these statements may be blanket statements. I understand there are exceptions.

First let me say, regular roof maintenance is necessary to achieve the full potential of your flat roof. Regular inspections; no longer than 5 years between inspections. You don’t wait until your engine blows before you change the oil. You maintain it regularly to ensure it performs to its maximum potential. But, your roof costs as much or more than your car, it protects what may be the single largest investment you ever make. But yet the attitude is to be reactive as to proactive. You wait until it breaks before you even think consider maintenance.

A roof is a perishable item. It has a life expectancy. And as anything with a life expectancy, it relies on maintenance. A roofer is to a roof what a doctor is to a human. If you have regular visits, problems can be diagnosed and your roof will be healthier, live longer and reduce the risk of interior damage.

But, in most cases, when we try to discuss these items with an owner, we are viewed as slick salesmen just trying to take them for more money. We are trying to educate you and save you money over the long run.

With that said, I would recommend a single ply, heat weld system. I prefer these systems when the slope is under 1/4". A knowledgeable salesman will be able to help you choose the proper material for your application. You may also consider a modular living roof. The initial cost is on the high end but Green Roof Blocks and similar products are reusable. greenroofblocks.com

The views and opinions stated above do not necessarily reflect the views or opinions of The South Side Group, LAC. St. Louis’ Roofing and Weatherproofing Specialists.(Shameless Plug)lol

I didn’t know that I was supposed to do maintenance on the edge of the roof. I periodically did go up on the roof to clean accumulated leaves and debris. Checked the flashings and such too. But I didn’t know that I had to check the perimeter of the roof as well. I’ve never seen that done before or had anybody tell me about that. Had I known that this was the case I would have done it.

Just so you know, most commercial low-sloped roofs that have a manufacturer’s warranty on it require quarterly or annual inspections depending on the manufacturer. These inspections can be done in-house, so it doesn’t mean it has to be done by a roofer or consultant. Of course, the purpose of the inspection is for someone with roof knowledge to look at the roof so it can be maintained; I do a lot of that as part of my job.

Now, if the contractor did not prime the metal or scuff it (assuming it was pre-finished), then the flashings are not going to stick very well.

Wouldn’t mind seeing photos.

You may want to check into Bligh Pacific Roofing, I know they are in your area, but I don’t know if they do any residential work. They did repair work for me in Santa Fe Springs, but to be honest all I saw was a bunch of digital photographs when the work was done. Still, based on the photos it appeared they do good work. If they don’t do residential, maybe they can point you in the right direction.

And just remember, the redundancy of a built-up roof system provides you protection that can not be offered by a single-ply. When water gets by the first ply on a built-up roof, the mod. bit. cap sheet, then you still have the built-up membrane protecting your building. However, when water gets by the first ply of a single-ply roof, there is nothing else to stop the water from leaking in to your building. If you maintain the built-up roof it should last you 20+ years, and you can repair any blisters, entrapped water, etc. that you find.

What is the difference between APP and SBS? Those are the two polymers generally used to modify asphalt and make it more elastic. Basically, but not always, SBS membranes are mopped down in hot asphalt and APP membranes are torched-down with propane torches. Most likely you have an SBS mod. bit. already, which means it has likely lost 40% of its granule-surfacing if it is 10+ years old. You also probably notice end laps that have shrunk, and your separation along the perimeter edge may also be from where the membrane flashing was mopped down. APP’s being torch-applied get heat-fused to the substrate, they weather much better than SBS’s, and they don’t shrink as much (all roofing membranes shrink).

One more thing. You may want to check into installing insulation with your new roof. The stimulus provides for up to $1500 dollar-for-dollar in some cases, though I don’t know if it would apply to you. Certainly something worth looking into though, as it would help reduce any A/C or heating bills you may have. I know, I know, you live in SoCal, but certainly you run the heat or A/C some time. :smiley:

A “BUR” roof is neither of what you described. A “BUR” is a hot mopped roof. It can be 3 or 4 ply. Then on the final flood coat the hop mop has gravel embedded.
What you are describing is simply 2 different modified systems.

[quote=“roofrite”]A “BUR” roof is neither of what you described. A “BUR” is a hot mopped roof. It can be 3 or 4 ply. Then on the final flood coat the hop mop has gravel embedded.
What you are describing is simply 2 different modified systems.[/quote]

Perhaps you should read the thread again.

Your first priority should be finding a good roofer. Next would be to find a good inspector to check up on the roofer.
Modified, BUR, Single Ply, are all good systems when installed by a competent roofer. And the above is good information.

My preference is copper, then single ply. Only because the detailing of single ply(I’m sure you would not be using copper), in my opinion, can be done with much more care and finesse and will look much better on a residential home.

"Is it better to go with a 4ply (base, 2 11 lb. plys, granulated cap sheet) or a 5ply (base,3 11 lb. plys, granulated cap sheet)BUR? "

I guess I don’t understand what is being said then Axiom. The above statement looks to me like look like modified systems. He has them both finishing with granulated cap. You tell me what am I missing?

go with a pvc single ply membrane or if your in a northern climate EPDM. Its a better roof for the money. although a BUR is also an exellent roof.

There seems to be some disagreement regarding single ply vs. multi ply systems among guys who are very knowledgeable. If anyone is in the mood to givea dissertation I’m all ears. If not thats ok too I know I ask for them often :mrgreen:

[quote]I guess I don’t understand what is being said then Axiom. The above statement looks to me like look like modified systems. He has them both finishing with granulated cap. You tell me what am I missing?

Roofrite, maybe I’m the one who doesn’t understand the difference. The roof that is currently in place was “hot mopped” . It has the 28lb based sheet nailed to the deck. Then 3 plys of 11lb sheet, hot mopped in between each layer. Then INSTEAD of rocks, I had a granulated cap sheet hot mopped on top instead. I didn’t want the rocks. I thought that was a BUR, not a modfied. Maybe I am mistaken.[/quote]

Racerx where I am from we refer to only those roofs that finish with garvel embedded in the final coat of hot mop as a (BUR) built up roof. What you are describing is a particular version of a modified system. Modified can be hop moppped,torch down, cold process applied or peel and stick. But they are all modified systems with different application methods. Hot mopped is tpically is the best system in my opinion. But it seems less and less people do them these days due to various reasons. It may be possible to cut back the membrane all around the perimeter and repair the rotted fascia board and decking and then install new membrane. This can be a tricky repair but not impossible I would only do such a repair for a premium price because it is almost easier to rip everything off and just start over.

hey racerx,
like the user name.
are you some famous race car driver in la.
none the less.
i havent used mopp grade granulated cape(mop grade modified),
in over 20 years. 2 things. it shrinks, and the granuals flake up and wear off, in pounding areas,
in a couple yrs. nothin wrong with the bur. or torch.
they are totally different animals.

im sure the edge leaks were simple fixes when they started.

bur 3ply, coated wht or silver(your community im sure would like brite wht.)
or torchdown is good too.
but please stay around the house for several hours
after roof is torched on.

and also look into peal n sticks.

there green.


[quote=“roofrite”]"Is it better to go with a 4ply (base, 2 11 lb. plys, granulated cap sheet) or a 5ply (base,3 11 lb. plys, granulated cap sheet)BUR? "

I guess I don’t understand what is being said then Axiom. The above statement looks to me like look like modified systems. He has them both finishing with granulated cap. You tell me what am I missing?[/quote]

It’s probably a regional thing.
When I read the description of the roof, to me it is a 3 ply BUR with a modified cap sheet.

When I used to do BURs we would finish them with pea stone, flood coat them, or use a SBS cap sheet.
I was taught that all 3 ways was a BUR.

For some of the modified systems we would sprinkle mop the insulation then mop down a base sheet then apply an APP modified, with a torch.
Sometimes we would torch smooth modified then cap it with a granulated modified, over the mopped down insulation and base sheet.

Sometimes for the modified systems we would mechanically attach the insulation and base sheet then torch apply the midply and cap sheets.
I was taught that the last 2 examples are modified systems.

Personally I think that a properly applied BUR is the best flat roof in most cases.

Roofrite, I agree with you on taking the whole thing back off and starting over. I’ve gotten quotes to also do a repair as well as tear off and re-roof. I think that if a repair is done you will create more of a chance for ponding, because I believe that the perimeter would be slightly higher than the inside. I like lakes too, just not on my roof. :smiley: We are expecting a LOT of rain here in the next week. So my roof is tarped off right now. As soon as the rain disappears I’ll take some pics and everyone can get a better grasp as to what is going on.

Why not look into IB roof systems ? they have an exelent nice heat weldable, clean single ply membrane.
lifetime warranty on residential 25 year on commercial. I like them better than Sarnafil. modifed bitumen either app or sbs id becoming a dinasaur, in this part of the country anyway.

What do you want to know?

I started off as a roofer installing the roof on the then new Nissan Truck Mfg. plant in Smyrna, TN. The roof consisted of 1-layer fiberglass insulation screwed to metal roof deck, a second layer of fiberglass insulation mopped down in hot asphalt, 4-plies of coal-tar pitch, and slag surfacing. That was back in 1981 if memory serves me correct.

Since then I’ve installed lots of BURs, but eventually became the company’s primary foreman for Carlisle EPDM roof installations; though we always did our own sheet-metal work. After some 7 years for the one company, I moved on up to NoVa and went to work for a company that did roofing and waterproofing. I’ve done below-grade waterproofing with Bituthene and American HydroTech, installed drain tile, French drains, drainage boards, etc. I’ve also installed Firestone EPDM, GRM, 3M, Sarnafil PVC, Vulkem plaza deck/planter waterproofing, epoxies, etc.

After that I went into consulting, back to roofing, and then on to consulting to stay. So, I’ve not only worked with the materials first-hand for over 12 years, I’ve also specified materials for around 15 years now. Having worked with most and specified several, I can tell you I prefer a built-up roof with a mod. bit cap sheet if done correctly over any single-ply membrane. It is more durable, tougher, and has redundancy you don’t get with a single-ply. A single-ply just offers a cleaner, easier solution, but without the longevity of a built-up roof.

Come on now longevity ? there are single ply roofs around here that were installed in the 70’s and are still good. Then again from what I understand the Boston area is the most known area for single ply roofing in the country. I do know from my traveling union days that the Boston area union roofers seemed better trained than roofers from other parts of the country by a long shot, but maybee im just prejudice.
The fact is that a single ply can save you money and last for over thirty years.