Modified bitumen vs 60 mil EPDM membrane Flat Roof


#1

My husband and I have received two estimates to replace our flat roofs(lower roof 14’x17 1/2’ upper roof 34 1/2 x 17’). We are now trying to decide which roofing co. we should hire to replace our two flat roofs on our 1890 brownstone.

The first estimate proposes to install the following for $11,960.00 (Firestone 60 mil EPDM membrane):
-Install 1/4" Dens deck Prime roof insulation mechanically fastened to the roof deck.
-Install Firestone 60 mil EPDM membrane, fully adhered to insulation in accordance with the manufacturers 20 year specifications.
-Install new flashing at all perimeters, curbs, and all roof penetrations.
-Install shop fabricated .032 brown aluminum coping, drip edge, and counter flashings and terminations.
-Install 6" ogee brown aluminum gutter and 4" aluminum downspout to replace existing at rear.
0Workmanship guranteed against leakage for two years.

The second estimate proposes the following for $16,491.00 (3 ply modified
bitumen roof system):
-Provide and install new perimeter edge metal.
-Provide and install 3 squares of fiberglass base sheet.
-Provide and install 3 squares of SBS modified bitumen smooth surface modified bitumen roofing installed in a cold applied fashion.
-provide and install 3 squares of SBS granular surface modified bitumen roofing installed in a cold applied fashion.
-Provide and install 14 feet new SBS modified bitumen granular sufaced wall flashing.
-Provide and install all new base flashings to the roof curbs and chimneys.
-Provide and install .032 aluminum counter flashing where needed.
-Provide and install new pitch pocket flashing to the conduit lines.
-Provide and install loose granules to the bleed out of all seams.
-Provide an exclusive lifetime guarantee/warranty for manufacturing defects and misapplication.

I’m not sure if one product is superior to the other (3 ply modified bitumen vs/ 60 mil EPDM membrane) to justify the difference in price or if one company’s proposal is superior to the other? We live in D.C. so the weather is not too extreme. We do have a large tree in the rear of our yard but it doesn’t hang directly over the roof so it really shouldn’t be a problem (unless lightening strikes it or some other act of nature). -Are there any other questions I might want to ask either company when comparing their bids? Each company has a very good reputation and have both been around for a long time. -Any advice or insight is greatly appreciated since I’ve never owned a house with a flat roof before.

                              -Thanks,
                                         DG

#2

Both roofing systems are very good.

I would choose .60 mil EPDM over SBS modified.
I would choose APP modified over both.


#3

Definately the 60 mil EPDM. Fewer seams, less trouble


#4

For pricing comparisons, where are you located? I agree that less seams = less possibility of leakage or seam failure.

You should also ask about the tools they use to install; some co’s just pull tight by hand while others use weighted rollers (better).


#5

:slight_smile: Thanks for all the replies!! -You guys are awesome.

   -Ranch hand, we live in Washington D.C.  The bids also took into consideration the fact that we have NO Rear access to the back of our house.  The only way to get to the back is through our basement or going from the front of the house over the top of the third floor roof.

#6

The rear end access is an item a lot of people don’t think to mention when they give us comparitive prices.

I have no idea what your market prices should be, so I’ll let folks who are more in the Midwest or Central Atlantic states help on that area.

PS: Are you DC proper, Maryland or Virginia? I lived for a short while with my Dad in Newport News (Langley) & Alexandria (Fort Belvoir).


#7

I left you a more detailed answer where you posted earlier at DIY. EPDM was my favored system, but I also pointed out a few other things like numder of layers and type of existing roof(s) to consider. It might need a tear-off.


#8

Ranch hand: We live in DC proper on Capitol Hill. We are renovating an 1890 brownstone.

Tinner 666: Both roofing companies bids included tearing off the existing roof or roofs (no one is certain how many roofs there may be until they do the tear down). I’m sorry I didn’t include that in my original post. There would also be additional charges for any rotted wood that would have to be replaced.

9


#9

When is this work to commence? Seems a bit cold out right now for these type of apps.

Also, once you get close to project time it might be worth it to do a partial teardown of a small corner or other area where you can see exactly how many layers you’ve got up there & then you can compare prices on a full teardown (totally accurate repairs on an as found are obviously impossible).


#10

If you see your roofer stretching the EPDM you should fire them all immediately.
If they do this they obviously don’t have a clue as to how to apply EPDM.


#11

I personally think you should follow up on the other system suggested in the DIY forum you posted this same question at.

Hot air welding is different than open flame torch down roofing.

The heat from a glorified hair dryer actually melts and molecularly fuses the two lap joint seams together.

If you had suggested that one of the installers had recommended that type of membrane, I would have said that would be the preferable choice.

You mentioned this was a row house.

Are there fire-walls built between the seperate units? If so, and if they are like the Chicago row houses, this would be a great alternative.

It is also easier and more forgiving to install in colder temperatures.

Ed


#12

ditto Axiom,

try to get the wood thrown in with the deal.

gweedo.


#13

I agree that the modified system is the more durable of the two. Couple things from that quote…

The second estimate proposes the following for $16,491.00 (3 ply modified
bitumen roof system):
-Provide and install new perimeter edge metal.
-Provide and install 3 squares of fiberglass base sheet.
A three ply system to me is 3 plys of modified. Have them lose the fiberglass base and substitute the Firestone modified nailable base sheet.

-Provide and install 3 squares of SBS modified bitumen smooth surface modified bitumen roofing installed in a cold applied fashion.
-provide and install 3 squares of SBS granular surface modified bitumen roofing installed in a cold applied fashion.
-Provide and install 14 feet new SBS modified bitumen granular sufaced wall flashing.
-Provide and install all new base flashings to the roof curbs and chimneys.
-Provide and install .032 aluminum counter flashing where needed.
-Provide and install new pitch pocket flashing to the conduit lines.
-Provide and install loose granules to the bleed out of all seams.

-Provide an exclusive lifetime guarantee/warranty for manufacturing defects and misapplication.
As far as I know Firestone still does not warranty residential work so most likely this warranty is from the roofing contractor. I’d ask about it.


#14

[quote=“Tar Monkey”]I agree that the modified system is the more durable of the two. Couple things from that quote…

-Provide and install 3 squares of SBS modified bitumen smooth surface modified bitumen roofing installed in a cold applied fashion.
-provide and install 3 squares of SBS granular surface modified bitumen roofing installed in a cold applied fashion.
-Provide and install 14 feet new SBS modified bitumen granular sufaced wall flashing.
-Provide and install all new base flashings to the roof curbs and chimneys.
-Provide and install .032 aluminum counter flashing where needed.
-Provide and install new pitch pocket flashing to the conduit lines.
-Provide and install loose granules to the bleed out of all seams.

-Provide an exclusive lifetime guarantee/warranty for manufacturing defects and misapplication.
As far as I know Firestone still does not warranty residential work so most likely this warranty is from the roofing contractor. I’d ask about it.[/quote]

3 squares still is not the actual amount of your 2 roofs, as I responded to you in the other DIYchatroom dot com forum. Get that to read correctly.

I agree that a 3 ply mod-bit roof is more durable.

I do not think Firestone has a residential warranty, except for “Material” defects also.

The IB Roofing system that some other posters suggested on the other forum does have a residential warranty though.

Ed


#15

[quote=“doingygirl”]:slight_smile: Thanks for all the replies!! -You guys are awesome.

   -Ranch hand, we live in Washington D.C.  The bids also took into consideration the fact that we have NO Rear access to the back of our house.  The only way to get to the back is through our basement or going from the front of the house over the top of the third floor roof.[/quote]

Ah, my old romping grounds. I grew-up in Fairfax and later lived in Oakton, VA and Wheaton, MD.

Anyway, you have some good roofers in your area, but you should be careful who you pick as a contractor. As for the type of roof, I would prefer an APP modified bitumen over the SBS, but I definitely prefer the SBS modified bitumen over the EPDM roofing membrane. If I was doing the work myself, it would be one thing, but if anyone else is doing the work I would go with a system that is more forgiving. The modified bitumen is going to take a lot more abuse from foot traffic, ice, sleet, hail, falling branches, etc., than the EPDM. Heck, the cap sheet on the modified bitumen alone is probably between 160 - 180 mils, whereas the EPDM (rubber) is only 60 mils.

Now lets get more specific. I’m going to guess the second roofing contractor plans on using MBTechnology’s roofing materials on the SBS modified bitumen roof. Can you confirm? And, if you send me a private message, I’d be curious which contractors you are getting bids from. I’ve been gone from the D.C. area for 11 years now, but I still remember several of the contractors (assuming none of them went under).


#16

TPO is my personal fav.
But of these 2 options, EPDM all the way!

1/4" insulation??? They should at least give you 1/2".

This price sounds high. 1K per sq for .060 EPDM is high no matter what the access. 2 years isnt a very good labor warranty either!

Which brand of EPDM are they going to use? Remember that there isnt any manufacturer’s material warranty if the contractor isnt an authorized installer.

I had a customer recently contact me about a Genflex TPO failure on a 50sq building. The roof is only 3 years old, but the TPO has cracked so badly that is has began to leak. The contractor wasnt a Genflex authorized contractor, so there is no material warranty. Needless to say, the customer is upset that he has to pay 25K to get this fixed, after forking out 30K a few years ago.


#17

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#18

or you could install a durolast roof.hell,you can become an approved installer yourself!!! :smiley:


#19

Its been said on here before but preference can be somewhat regional depending on how well the local roofers are trained. EPDM when done correctly is heads and shoulders better than any modified or glorified rolled roofing product.


#20

Not even close. Modified bitumen roofs when done correctly are much better than an EPDM roof done correctly. If you want to go with a single-ply roof system, you need to look into TPOs or Sarnafil’s PVC roofs. At least with these type single-ply roofs the laps are heat-fused instead of adhered.

BTW, though I am now a consultant, I used to put down a lot of Carlisle and Firestone EPDM roofs. I’ve also installed a couple Goodyear and Mulehide EPDM roofs, and repaired an old Gates EPDM roof. Regardless, I can tell you as an old EPDM-roofer (I also installed BUR, Mod Bits, etc.) that modified bitumens are better than EPDM roofs. And as a consultant, I can tell you that I will almost always specify/recommend modified bitumens over EPDM roof systems.