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Discussion Forum

Which is a better roof system?

| Posted in General Discussion on March 9, 2001 07:13am

*
Hi All, I am new to this message community, but I have been subscribed to FineHomeBuilding for about 9 years.

I’m trying to decide what the best roof I should get for a rental property I have, that is leaking.

1) Here’s what I’ve got: 28’x30′ parapet flat roof with 3 layers of old roof. I think the main problem is with the drain scupper, since that is where the leak is showing up inside the apartment. There are 8 vents piercing the roof.

2) The building is located in Long Beach, Ca.

3) I plan on keeping the building for quite a while, but want to pay as little as possible.

And

4) The roof never seems to leak on sunny days! (ok, so I’m sarcastic)

I plan on removing the old layers of roofing, and start fresh, and I will be using a licensed contractor. My question relates to what seems to be two competing roof systems: Hot Mop and Modified Bitumen.

I don’t have any realtime experience with either, so I was hoping I could get some suggestions from you guys.

Thanks for the input,
Jon

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Replies

  1. Bill_Pickard | Mar 05, 2001 09:06pm | #1

    *
    b TVMDC

    There is no argument that hot-mopped tar (Built-Up-Roof) is initially cheaper than a Modified Bitumen Membrane. But since you will be replacing the roof every 5-10 years, you will quickly realize that the LIFE cost of a well-installed Modified roof is about half that of hot-mopped tar.

    In addition, the membrane I use (Polyglass) comes with a full 12 year mfgrs warranty for material and labor for certified installers. Other mfgrs offer similar warranties. The is not one mfgr of hot-mopped systems who will come close.

    Besides, chasing leaks on a BUR is a near impossibility: stick with modified.

    1. Mike_Smith | Mar 05, 2001 09:26pm | #2

      *modified is branching out.. you can do a peel and stick modified..a trowel modified ..or a torch -down modified..you can also consider EPDM (rubber membrane) .060 or .045...fully- adhesed..all of these systems can go down over plywood or hardboard.. with built-in insulation or without..the modifieds are all granular surface.. more attractive tha the epdm...

      1. Jason | Mar 05, 2001 09:32pm | #3

        *I've used the modified peel and stick three times now with great success. Very easy to use; any idiot, including me, can do it. I've avoided these situations up to now simply because of how difficult hot methods and glue-down looked. Up to this point I'd done nothing but metal and shingles. Oldest one is going on four years with no leaks, so...

        1. Nick_Pitz | Mar 05, 2001 11:56pm | #4

          *We just had our roofing sub do one of our customer's flat roofs... it had a an terne roof covered with two hot mops and a foam coating... and it still leaked. We tore it off down to the sheathing and did a torch down modified... it cost quite a bit, but it was worth it... peace of mind, and fixing all the problems with it that the other roofs couldn't.

          1. Jon_Grossgold | Mar 06, 2001 12:30am | #5

            *Do you have any reference material on the peel-n-stick solution? A name of manufacturer or distributer?Thanks,Jon

          2. Mike_Smith | Mar 06, 2001 01:08am | #6

            *i've used two..one is Lo-Slope by Monsey.. uses a water-base primer.. offers 10 year in single coverage... and 15 year in double coverage..the other product i like even better..Colphene by Soprema , uses a toluene based primer..more of a ""welded"" seam..the water base is more forgiving in damp cold conditions for applicationthe Colphene, is probably the better product, but both are pretty awesome... about $50 a sq. plus primer..you can use them without primer.. but i like the superior adhesion we get with the primer..you need a smooth base.. like plywood, or a concrete deck or a steel roof.. since the bond will only be as strong as the material it is adhered to...b but hey, whadda i no ?

          3. JRS | Mar 06, 2001 02:09am | #7

            *Jon,One of my specialties is commercial flat roofing. Here is my take: I have installed lots of hot-mop, modefied, and EPDM roofing. I believe strongly that the proper EPDM system for any given roof is the best. But the most important thing you can do is find a quality oriented contractor to install whatever system you decide on. The best system can be easily screwed up, rendering it useless.Far too many variables to consider for me to give you an easy, pat, answer as to what system is best for b your roofWatch out that item #3 on your list doesn't get you in trouble!John

          4. Jan_Goossens | Mar 06, 2001 06:09pm | #8

            *I agree with JR, I grew up in Belgium (where it rains on average 200 days a year and yes with this weather, one can make a living installing flat roofs). My dad owned a commercial roofing/ siding/ insulation company and before moving to the US (20 years ago), I've installed my share of roofs. Mostly torched down APP and SBS. Is your roof concrete, steel or wood? The first two you have to prime, it makes a chemical bond with the newly installed membrane, instead of a mechanical one. The latter should have a floating membrane weighed down with pebbles or a first layer (a 3mmm (fiber-glass based)), nailed down in a diagonal fashion so the lumber can expand/shrink without ripping the upper layer. When using polyester based APP/ SBS or EPDM (all have characteristics to overcome these tensions) you should be fine. When using APP (because of it's higher melting point, I'd prefer APP in your neck of the woods) or SBS get it minerelized (it's a UV protector - The life cycle of these modern membranes is much longer than their warranties - upwards of 30 years. Roofs I installed in the late '70s are still not up for renewal. It is essential you find a quality installer, most small roofers lack the knowhow and most big commercial ones find a relative small job not worth their while.

          5. Ron_Rosa | Mar 07, 2001 12:52am | #9

            *You need to have at least a 1/12 to use modified and be backed by the manufactor's. The only true great modified system includes a hot mopped membrane under it . EPDM is a great product but you pay for it. Good Luck. Most problems occur with leaking drains because they are not installed lower than the roof surface , water just puddles around it. Have your roofer re install the drain lower than the current level{Recessed}.

          6. Stray_ | Mar 08, 2001 10:36pm | #10

            *Old layers may contain asbestos.... in New York, it doesn't add much to the cost of the tear off, just disposal costs increase slightly. Of course Calif may certainly be different. Something to think about before you rip it off.

          7. Tim_Kline | Mar 09, 2001 07:13am | #11

            *b WBA At Your ServiceMy uncle is a retired VP from GAF and he and I have fought a few battles over Thanksgiving turkey. One major point I have learned from him is that we in PA live in the rubber capitol of the world being so close to Carlisle PA. Carlisle Rubber's big marketing push started close to home and as a result it's hard to find people to do hot mopped jobs around here. He claims California is totally different in that built-up roofs are much more popular there. Once a roofer discovers the ease of rubber and the fun glue fumes compared to kettle stink, it's hard for them to go back. While I like rubber (EPDM or whatever you want to call it) I've seen a LOT of failures with it when used over existing old roofs. It's always the field applied seams. If it were my own roof, I would have a hard time choosing between 4 ply built up and rubber. I have seen many built ups in service for 30 or 40 years that still looked good.

  2. Jon_Grossgold | Mar 09, 2001 07:13am | #12

    *
    Hi All, I am new to this message community, but I have been subscribed to FineHomeBuilding for about 9 years.

    I'm trying to decide what the best roof I should get for a rental property I have, that is leaking.

    1) Here's what I've got: 28'x30' parapet flat roof with 3 layers of old roof. I think the main problem is with the drain scupper, since that is where the leak is showing up inside the apartment. There are 8 vents piercing the roof.

    2) The building is located in Long Beach, Ca.

    3) I plan on keeping the building for quite a while, but want to pay as little as possible.

    And

    4) The roof never seems to leak on sunny days! (ok, so I'm sarcastic)

    I plan on removing the old layers of roofing, and start fresh, and I will be using a licensed contractor. My question relates to what seems to be two competing roof systems: Hot Mop and Modified Bitumen.

    I don't have any realtime experience with either, so I was hoping I could get some suggestions from you guys.

    Thanks for the input,
    Jon

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