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Old 06-01-2011, 08:10 AM   #1
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Bakor 1 ply vs Torch down


I have a low slope 1:12 on the back of my house. The roof is Dibiten (if I recall the name correctly) It is torch bonded and has worked for 22 years. It has no granules. The deck is plywood. I need to have the Dibiten replaced. One roofer wants to use Bakor 1 ply, with a sticky back after stripping the existing roof. Is this product suitable and can it be removed in the future or does it adhere to well to the plywood? The Bakor website does not seem to have any application information for this product. Another contractor wants to put a one ply torch down with granules on the existing roof without stripping it. I am concerned with the additional weight as the plywood is rather thin.

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Old 06-01-2011, 12:41 PM   #2
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Bakor 1 ply vs Torch down


If its over a living area I wouldnt do a self adheard cap sheet, I would atleast use a base then the cap sheet. If you nail the base down you will be able to remove it. For the torch down, he wasnt to put a flame to your old roof and just cap sheet over it. Not a very long lasting roof you wont get 22 years out of caping it. I wouldnt worry about the weight it *should be* ok. If it is over a living area you could put some insulation down and then a single ply EPDM, TPO or PVC, depending on what you want to spend.

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Old 06-03-2011, 08:45 AM   #3
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Bakor 1 ply vs Torch down


I am not familair with Bakor. I assume it is a type of single ply membrane. But there are lots, EPDM, PVC, TPO, etc...

If I were to strip the roof I would not install directly to the plywood. I would install a seperation, called a cover board, such as a high density fiberboard or preferrably a high density ISO. There are numerous reasons for this. If the plywood wasn't properly installed, meaning that it wasn't screwed instead of nailed, the nails will back out right through the plywood. The manufacturers have specifications for installing directly to plywood but you have to adhere to those specs. Also a typical grade C plywood wouldn't be my first choice. At least B, but preferrably A. Installing new plywood would cost most than it's worth so see my original comment about the HD fiber or ISO boards.

If R value is a concern I would instead install Poly Isocyanurate insulation board (assuming the ceiling is notinsulated in this area as I would not want to create a warm pocket. If the ceiling is insulated and isulation is still a concern, have some of the plywood removed and fiberglass installed, now is the time.



As for torching the new modified over the existing, I do not know how many layers you have now so can't comment about weight nor code. What you should understand about modified bitumen is that it is somewhat like a built up roof in the fact that it is comprised of multiple layers. A typical modified bitumen roof may only be two layers, a base sheet and a cap sheet. Depending on base and cap this may only be a 10-15 year rated roof. If you were to install a base sheet and a smooth mid ply, like what you have now, and then install a granulated cap over that this would be rated as a 20 year roof (at time of original installation).

Have we ever torched a cap over a existing smooth modified? Yes we have, but never oer a 20 year old modified. i wouldn't expect them to last 20 more years however. Maybe only 10-15 years max. I can't see how the old roof lasted that long unless you were coating it. If you were coating it this may be a problem for torch adhesion. If you wern't coating it and want to go over, I would apply a coating of asphalt primer first before torching just to soak into the weathered nooks and crannies and cracks of the existing modified bitumen membrane.

Personally if I were your roofer normally this is how I approach most residential jobs. 1) tear it off. You always get a better job when you tear it off. 2) If the flat roof is not visible and doesn't tie in with the shingles, meaning the flat roof ends at a wall or something, then I would be recommending single ply like TPO, PVC or EPDM. 3) If the roof is visible and you don't like the look of single ply I would be recommending modified bitumen with a granulated cap sheet. Normally I like to install self adhering on wood structures, if there is any vinyl or wood siding directly in my work area there is no way I will torch. Self adhering will cost slightly higher than torch however. 4) If the roof meets with the shingles I would be reocmmended a 3 ply self adhering modified bitumen roof system. Why 3 ply? Because this is rated at 20 years and it would be a bad idea to install a 15 year rated flat roof with a 30+ year rated shingle.


Here is a good read on my website which can explain more about various Flat Roofing Options


let's talk about accessories because a roof is just not the membrane. You need to also factor in the accessories such as terminations. For example who is isntalling what at the edges of the roof? There shold always be some kind of metal termination around all edges. This is commonly a gravel stop or drip edge at the gables, a termination bar our counter flashing at walls, and of course gutter. There are a few threads on this forum that discuss flat roof gutters. If someone is not approaching the roof as a system, more than just the membrane, they are installing an incomplete roof.
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Sometimes the savings that comes from doing it yourself can be blown away with one mistake.

The information found in this post is not to be considered legal advice. All information should be considered relative, not specific. Never attempt any repairs you are not comfortable with. Always maintain safety! The author of this post takes no responsibility for any losses that occur. Use at your own risk.
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Old 06-03-2011, 10:42 AM   #4
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Bakor 1 ply vs Torch down


Quote:
Originally Posted by Grumpy View Post
I am not familair with Bakor. I assume it is a type of single ply membrane. But there are lots, EPDM, PVC, TPO, etc...

If I were to strip the roof I would not install directly to the plywood. I would install a seperation, called a cover board, such as a high density fiberboard or preferrably a high density ISO. There are numerous reasons for this. If the plywood wasn't properly installed, meaning that it wasn't screwed instead of nailed, the nails will back out right through the plywood. The manufacturers have specifications for installing directly to plywood but you have to adhere to those specs. Also a typical grade C plywood wouldn't be my first choice. At least B, but preferrably A. Installing new plywood would cost most than it's worth so see my original comment about the HD fiber or ISO boards.

If R value is a concern I would instead install Poly Isocyanurate insulation board (assuming the ceiling is notinsulated in this area as I would not want to create a warm pocket. If the ceiling is insulated and isulation is still a concern, have some of the plywood removed and fiberglass installed, now is the time.



As for torching the new modified over the existing, I do not know how many layers you have now so can't comment about weight nor code. What you should understand about modified bitumen is that it is somewhat like a built up roof in the fact that it is comprised of multiple layers. A typical modified bitumen roof may only be two layers, a base sheet and a cap sheet. Depending on base and cap this may only be a 10-15 year rated roof. If you were to install a base sheet and a smooth mid ply, like what you have now, and then install a granulated cap over that this would be rated as a 20 year roof (at time of original installation).

Have we ever torched a cap over a existing smooth modified? Yes we have, but never oer a 20 year old modified. i wouldn't expect them to last 20 more years however. Maybe only 10-15 years max. I can't see how the old roof lasted that long unless you were coating it. If you were coating it this may be a problem for torch adhesion. If you wern't coating it and want to go over, I would apply a coating of asphalt primer first before torching just to soak into the weathered nooks and crannies and cracks of the existing modified bitumen membrane.

Personally if I were your roofer normally this is how I approach most residential jobs. 1) tear it off. You always get a better job when you tear it off. 2) If the flat roof is not visible and doesn't tie in with the shingles, meaning the flat roof ends at a wall or something, then I would be recommending single ply like TPO, PVC or EPDM. 3) If the roof is visible and you don't like the look of single ply I would be recommending modified bitumen with a granulated cap sheet. Normally I like to install self adhering on wood structures, if there is any vinyl or wood siding directly in my work area there is no way I will torch. Self adhering will cost slightly higher than torch however. 4) If the roof meets with the shingles I would be reocmmended a 3 ply self adhering modified bitumen roof system. Why 3 ply? Because this is rated at 20 years and it would be a bad idea to install a 15 year rated flat roof with a 30+ year rated shingle.


Here is a good read on my website which can explain more about various Flat Roofing Options


let's talk about accessories because a roof is just not the membrane. You need to also factor in the accessories such as terminations. For example who is isntalling what at the edges of the roof? There shold always be some kind of metal termination around all edges. This is commonly a gravel stop or drip edge at the gables, a termination bar our counter flashing at walls, and of course gutter. There are a few threads on this forum that discuss flat roof gutters. If someone is not approaching the roof as a system, more than just the membrane, they are installing an incomplete roof.

Thanks Grumpy for the detailed reply.

My roof is nailed plywood, probably only 3\8" as it is soft to walk on. It does interface to shingles under a raised ridge at the top of the slope with the shingle caps being over the Dibiten. The original 1 ply, nailed, Dibiten had no gravel, I painted it with white latex after it was 4 years old to reduce the heat in the attic. The paint has mostly disappeared during the last years but I felt it did a good job and probably increased the life of the roof. The roof is insulated, that is there is insulation below the roof over the rafters. Twenty two years ago I removed the plywood down the middle and added fiberglass insulation, leaving a few inches air space between the insulation and the deck. I also re-nailed the plywood with ardox nails and made sure there were no sharp objects anywhere before the Dibiten was layed by the roofers. There is metal flashing along the deck edges under the Dibiten but not at the bottom of the slope where the Dibiten was bent into the eavestrough. This seems to have worked well as far as insuring a drip edge and no water penetration at the edge. I am in Southern Ontario, Canada.
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Old 06-03-2011, 12:37 PM   #5
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Bakor 1 ply vs Torch down


Consider roof vents in addition to a white reflective membrane if you are concerned with heat inside the attic. I say this since you stated the roof is a cold deck, that the ceiling is insulated.

If the only tie-in with shingles is the ridge you would be fine with a single ply membrane. Tear it off, fix what ever may be rotten plywood, install a cover board and install a thermoplastic (tpo or pvc) single ply membrane. Depending on the membrane thickness and manner of installation, this may be a 15-20 year roof. Infact if you install the premium 72 - 80 mil membrane, fully adhered and double seam it, you have a 30 year rated roof. As you can imagine though, longevity costs money.
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Sometimes the savings that comes from doing it yourself can be blown away with one mistake.

The information found in this post is not to be considered legal advice. All information should be considered relative, not specific. Never attempt any repairs you are not comfortable with. Always maintain safety! The author of this post takes no responsibility for any losses that occur. Use at your own risk.
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Old 06-03-2011, 01:46 PM   #6
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Bakor 1 ply vs Torch down


Quote:
Originally Posted by Grumpy View Post
Consider roof vents in addition to a white reflective membrane if you are concerned with heat inside the attic. I say this since you stated the roof is a cold deck, that the ceiling is insulated.

If the only tie-in with shingles is the ridge you would be fine with a single ply membrane. Tear it off, fix what ever may be rotten plywood, install a cover board and install a thermoplastic (tpo or pvc) single ply membrane. Depending on the membrane thickness and manner of installation, this may be a 15-20 year roof. Infact if you install the premium 72 - 80 mil membrane, fully adhered and double seam it, you have a 30 year rated roof. As you can imagine though, longevity costs money.

I seem to have trouble getting local roofers to do TPO or PVC, they all say "very expensive" but not how much. Any idea on typical cost per sq foot?
So far quotes are around $3500-$4500 (500 sq feet) for what they want to do. Rates are much higher than normal I suspect do to a windstorm a few weeks back.
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Old 06-03-2011, 01:56 PM   #7
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Bakor 1 ply vs Torch down


LOL very expensive is WRONG when comparing apples to apples. What I mean is a 20 year spec on a TPO roof is substantially less than a 20 year modified bitumen. let's talk about material prices, a good quality 4mm smooth modified bitumen is $60 a square. You can find it for as cheap as $52. A 60 mil TPO is $57 a square. Sure there is more to it than just the materials, but you get the point.

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Sometimes the savings that comes from doing it yourself can be blown away with one mistake.

The information found in this post is not to be considered legal advice. All information should be considered relative, not specific. Never attempt any repairs you are not comfortable with. Always maintain safety! The author of this post takes no responsibility for any losses that occur. Use at your own risk.
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