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Old 06-11-2013, 12:11 AM   #1
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Help evaluating bids for a flat roof in San Francisco


Hello everyone,

I am the new owner of a SF home with a 1200 sq. ft. flat roof that is currently tar and gravel. The roof on it now was done in 1992 and is at the end of its life. The roof has a good slope on it and I don't have leaks as far as I know but it hasn't rained much since i've lived here. I've been up there and saw the tar underneath the gravel in a hardened state and in some locations there is some fiber material peeking through. Its time for a new roof. We plan on keeping this house "forever", either living in it or renting it when we grow out of it.

I got 3 bids to do this roof, each contractor came either highly recommended or has high reviews. Each contractor has slightly different preferred method of solving the problem. I'm completely stuck on who to pick.

Contractor one proposes:
1st layer #80 APP base fiberglass
2nd layer #180 APP finish granular using a torch-down method
4 year warranty
total cost $6500

Contractor two proposes:
1st layer certainteed flitlastic Self-Adhering but mechanically fastened base
2nd layer flintlastic Self-adhering Cap
5 year warranty
total cost $9000

Contractor three proposes:
Built-up-roof, 4 layers total: Fontana G-40 Base, 2 layers Certainteed Ply sheet and a Certainteed Cap
25 year warranty if 2 maintenance visits are agreed to and paid for (estimated at $600/ea. every 10 years, i.e. visit 1 at 10 years, $600, visit 2 at 20 years, $600) Warranty is also transferrable to a new owner.
total cost: $16850


Questions:
1. Is this an easy decision, if so who to pick and why?

2. I've been analyzing the lifecycle costs of each of these proposals but I don't think that I have realistic numbers. I am estimating that the first two roofs will need to be torn down and replaced at 15 years and the third roof will need to be torn down and replaced at 25 years. My lifecycle costs point to the same price relationship between the 3 contractors as the opening bids. Are my assumptions reasonable? Its is reasonable to analyze roof lifecycle costs over 30 years?

I'm not thrilled about the torch down method due to fire risk. I'm both enticed and wary of self-adhesive roof plies. And I feel like I'm overpaying for the 3rd, OR will get a great deal until he goes out of business.
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Help evaluating bids for a flat roof in San Francisco-img_20130527_093608.jpg   Help evaluating bids for a flat roof in San Francisco-img_20130527_093611.jpg   Help evaluating bids for a flat roof in San Francisco-img_20130527_091123.jpg   Help evaluating bids for a flat roof in San Francisco-img_20130527_090209.jpg   Help evaluating bids for a flat roof in San Francisco-img_20130527_085025.jpg  


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Old 06-11-2013, 08:45 AM   #2
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Help evaluating bids for a flat roof in San Francisco


You are going about this all wrong, but dont feel bad, most people do.

From your pictures, your problem is that your perimeter flashing's were never done correctly in the first place.

As far as your needing a new roof, I would appreciate some close up photos of what you are seeing that makes you think you need one.

None of the proposals you got indicate removal of the existing roof or flashings. That bothers me. I have not used an APP modified Bitumen in 20 or so years. Modified's formulated with SBS rubber are just too superior to even think about APP. Throw out No. 1.

I would not even think about using a peel and stick membrane on a low slope roof. Throw out no. 2

Right now No. 3 looks like the most responsible proposal, but as usual it is severely lacking in detail

Frankly, I do not see any ridging, or blistering in the field of your roof, so you may simply need to properly re-flash the perimeter, and install a metal coping.

You really need someone like myself to look at this, do a non-destructive survey, and give you some useful information by which you can make an informed decision. There are very few roofers (Present company excepted) that will tell you you don't need a new roof.

PS All of your flashing is deficient.

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Last edited by jagans; 06-11-2013 at 08:48 AM.
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Old 06-11-2013, 09:47 AM   #3
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Help evaluating bids for a flat roof in San Francisco


You are definitely going about it the right way by looking at life-cycle since you plan on keeping it long-term. Unfortunately most people, roofers included, have no clue what that is. 90% of my work is gov't entities and everything is about life cycle costing. Not knowing the details of your roof we can't speculate on what you are getting for your money but that's generally not the purpose of this forum.

I would also eliminate 1 and 2. They are ten-year roofs at best. I only recommend SA's for small, easy projects and tie-in's with other systems. ie dead valleys on shingles, porch/patios. BUR's are tried and true. Unfortunately only a small % of roofers are competent installers anymore since the advent of single-ply. Teach a monkey how to weld a seam and he thinks he's a roofer.

I'm actually agreeing with Jagans that, from the pictures your roof itself doesn't look that bad. We could be missing something though. Walls and curbs weren't done correctly which seems odd since it looks like a clean, decent install.

I don't know how good that certainteed cap is but your main issue over the life of their "warranty" will more than likely be de-granulation of that cap. Best thing to get the life out of it is inspecting it every five years or so and possibly coating it with a good acrylic periodically. A good 4-ply and gravel roof is a great long-term system. Just kind of a pain if they get a leak. BTW, who exactly is providing the warranties?

We have systems that, installed properly, will easily get you 30yrs worry-free but I don't know what they would cost on your roof.

Last edited by OldNBroken; 06-11-2013 at 09:49 AM. Reason: Hey look, my 1k post
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Old 06-11-2013, 10:10 AM   #4
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Help evaluating bids for a flat roof in San Francisco


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Last edited by OldNBroken; Today at 09:49 AM. Reason: Hey look, my 1k post
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Old 06-11-2013, 10:51 AM   #5
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Help evaluating bids for a flat roof in San Francisco


Hey guys,
Thanks for the responses. Let me fill in some info. All bids come will complete tear off of the old roof and disposal. The first proposal proposes to "heat weld the base sheet to the roof deck". This sounds like a no no. I believe i want my base layer mechanically applied.

Speaking of that, I peeked into my attic and found tar dripping from between the roofing boards, so perhaps the last (or previous roof) directly applied tar to the roof deck. What should I expect with that? Is this a bad thing?

All the warranties I have quoted are from the installer. Their warranties. I figured the manufacturer warranties were not really relevant since the manufactures will wiggle out of it somehow and point to the installation.

When I look at my existing roof, in some spots the gravel has been sparse and the underlying tar is rather alligator-looking, in some spots there you can see a weave fiber underneath the black tar. This is on the horizontal surface.

One question.... If the flashings were done wrong, something that is quite obvious, how can I possibly trust that anything unseen is done right? Meaning, some kind of refurb will be rather untrustworthy, correct?
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Old 06-11-2013, 11:53 AM   #6
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Help evaluating bids for a flat roof in San Francisco


I've never seen rock installed on top of perimeter walls like that, very interesting.

The asphalt dripping in to your attic could be two things, 1 they moped the first layer down. This is a huge no no on wood decks. Or they nailed a "felt" instead of a heavy base sheet down. Depending on the type of deck if you do not have any nails penetrating then you can assume they mopped the first layer down. If you have thicker decking this may not be the case. I would assume #1. and yes it's bad, bad for the person tearing it off, it will likely not all come off and shouldn't be a problem.

Contractor warranties are only as good as the contractor, be wary of a contractor who has been in business only 5 years and offering a 20 year warranty.

Some times gravel doesn't always bond well with the asphalt, simple fix is to get a bucket of mastic or cold app and stick the gravel back down. Seeing the fiber of the felts is because it's been unprotected for to long. The gravel is protecting the asphalt/felt from the sun. The reason you are seeing it on the wall flashing is because they are done wrong. Either they should have used a mineral surfaced cap sheet to flash with or a smooth cap sheet and coated it with alumacoating.

20 years is a reasonable amount of time to expect this type of roof to last, even much longer depending on maintenance. I like that about #3, they offer an extended warranty with a maintenance contract, this is something we often do our self. 25 years might be a bit much IMO, we offer a 10 or 15, but we walk the roof every year or twice a year.


I don't real like the use of mineral surfaced cap sheets. I would spec it like this.

Tear off all of the asphalt and gravel roof surfacing and flashing, and metal flashings down to the roof deck. Any areas firmly bonded in place (think completely mopped base sheet) will be scraped smooth.

Cap nail a fiberglass base sheet.

Install cant strip around all perimeter edges.

Mop 3 plys type 4 felt.
Mop 1 ply SBS smooth cap.

Install new metal flashings around all penetrations

Mop 1 layer of SBS base sheet on all perimeter walls lapping on to roofing felts approximately 6 inches and up the total height of the wall.

Mop 1 layer of SBS mineral surfaced cap sheet on all perimeter walls lapping on to roofing felts approximately 8 inches and up the total height of the wall. Color to be white.

Flood coat entire roof with asphalt and a full coating gravel.


Install EPDM over the top of the walls fasten cleat and install 24 ga prefinished cap metal.



This roof would likely run a little bit more then contractor #3's number but is easily a 25 year roof and could go a lot longer with maintenance.


And you are correct, torching to a wood roof deck is bad.
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Old 06-11-2013, 11:57 AM   #7
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Help evaluating bids for a flat roof in San Francisco


Quote:
Originally Posted by hey_bay View Post
Hey guys,
Thanks for the responses. Let me fill in some info. All bids come will complete tear off of the old roof and disposal. The first proposal proposes to "heat weld the base sheet to the roof deck". This sounds like a no no. I believe i want my base layer mechanically applied.

Speaking of that, I peeked into my attic and found tar dripping from between the roofing boards, so perhaps the last (or previous roof) directly applied tar to the roof deck. What should I expect with that? Is this a bad thing?

All the warranties I have quoted are from the installer. Their warranties. I figured the manufacturer warranties were not really relevant since the manufactures will wiggle out of it somehow and point to the installation.

When I look at my existing roof, in some spots the gravel has been sparse and the underlying tar is rather alligator-looking, in some spots there you can see a weave fiber underneath the black tar. This is on the horizontal surface.

One question.... If the flashings were done wrong, something that is quite obvious, how can I possibly trust that anything unseen is done right? Meaning, some kind of refurb will be rather untrustworthy, correct?
First of all, it would be good to find out exactly what kind of BUR you have.

In roof speak, Tar is Coal Tar Pitch, which is a bitumen which results from the destructive distillation of coal. Asphalt is the residue from the distillation process used to break down crude oil. It is a petroleum product.

From the looks of your roof, and the fact that you have dripping of bitumen from the roof deck, you may have a coal tar pitch roof.

To find out which one you have, take a piece of the bitumen and put it into a jar of mineral spirits. If it is pitch, the MS will turn yellow. If it is asphalt, it will turn brown.

Coal tar pitch has a softening point of 140 degrees, and will melt on a hot day, that is why they used to call it self-healing. Roofing asphalt can have different softening points based on the amount of oxygen that is injected into it. Coal Tar Pitch roofs are the Mercedes Benz of BUR's, and they are the only roof that is not broken down by ponding water, as pitch is not emulsified by H20. Unfortunately, you cannot have one, especially in California, because pitch is a carcinogen.

You are quite right in your logic in stating that they may have done other things wrong. It is completely wrong to mop or "Thermally Adhere" (that means torch) directly to a wood deck. I will go further to state that anyone who attempts to torch to a wood deck is not only incompetent, they are criminally insane, or at least criminally ignorant, and will probably burn your house down. Rosin seized paper is supposed to be laid down over a wood deck followed by a mechanically fastened base sheet, or insulation. This provides a shear plane which is absolutely necessary with a wood deck due to expansion and contraction.

As far as warranties go, I do not know any commercial roof manufacturer that offers a warranty on residential projects. It is just not worth it to them, as the amount of material that is used on a roof like yours is miniscule.

Your best warranty is a good specification, installed by a good contractor, and periodic maintenance, like cleaning the roof and drainage system of debris. You can do that yourself, you dont have to pay for it, unless you want to, and it should be done twice a year, depending on how many trees you have close to your roof.
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Old 06-11-2013, 02:26 PM   #8
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Help evaluating bids for a flat roof in San Francisco


Quote:
Originally Posted by 1985gt View Post
I've never seen rock installed on top of perimeter walls like that, very interesting.

The asphalt dripping in to your attic could be two things, 1 they moped the first layer down. This is a huge no no on wood decks. Or they nailed a "felt" instead of a heavy base sheet down. Depending on the type of deck if you do not have any nails penetrating then you can assume they mopped the first layer down. If you have thicker decking this may not be the case. I would assume #1. and yes it's bad, bad for the person tearing it off, it will likely not all come off and shouldn't be a problem.

Contractor warranties are only as good as the contractor, be wary of a contractor who has been in business only 5 years and offering a 20 year warranty.

Some times gravel doesn't always bond well with the asphalt, simple fix is to get a bucket of mastic or cold app and stick the gravel back down. Seeing the fiber of the felts is because it's been unprotected for to long. The gravel is protecting the asphalt/felt from the sun. The reason you are seeing it on the wall flashing is because they are done wrong. Either they should have used a mineral surfaced cap sheet to flash with or a smooth cap sheet and coated it with alumacoating.

20 years is a reasonable amount of time to expect this type of roof to last, even much longer depending on maintenance. I like that about #3, they offer an extended warranty with a maintenance contract, this is something we often do our self. 25 years might be a bit much IMO, we offer a 10 or 15, but we walk the roof every year or twice a year.


I don't real like the use of mineral surfaced cap sheets. I would spec it like this.

Tear off all of the asphalt and gravel roof surfacing and flashing, and metal flashings down to the roof deck. Any areas firmly bonded in place (think completely mopped base sheet) will be scraped smooth.

Cap nail a fiberglass base sheet.

Install cant strip around all perimeter edges.

Mop 3 plys type 4 felt.
Mop 1 ply SBS smooth cap.

Install new metal flashings around all penetrations

Mop 1 layer of SBS base sheet on all perimeter walls lapping on to roofing felts approximately 6 inches and up the total height of the wall.

Mop 1 layer of SBS mineral surfaced cap sheet on all perimeter walls lapping on to roofing felts approximately 8 inches and up the total height of the wall. Color to be white.

Flood coat entire roof with asphalt and a full coating gravel.


Install EPDM over the top of the walls fasten cleat and install 24 ga prefinished cap metal.



This roof would likely run a little bit more then contractor #3's number but is easily a 25 year roof and could go a lot longer with maintenance.


And you are correct, torching to a wood roof deck is bad.
1985GT has a good spec there, but it does not take into consideration the dripping bitumen, problem, and it does not state that you are going to need a pressure treated wood nailer and tapered edge on top of the parapet walls to terminate your base flashings, and secure your cleats for your metal coping, which should be sloped back toward the roof. Your flue stacks are going to need Stainless Steel Tall cone flashings, and you pipes need 3# lead pipe jacks. Im sure he knows all this stuff, it is just details, but a long lasting roof is in the details. It is pretty clear from his spec he knows his stuff.

I know you do not get excessively hot weather there in the bay area, but if you have thermal insulation in the current roof system, that may have prevented the bitumen drippage from becoming too bad. You really need to address that, so check to see whether that drippage is asphalt or pitch. Pitch is not a problem as long as you keep its temperature down.

You do not say where your thermal insulation in your home is located. This is important.
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Last edited by jagans; 06-11-2013 at 02:32 PM.
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Old 06-11-2013, 02:44 PM   #9
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Help evaluating bids for a flat roof in San Francisco


Thanks guys for helping to break the logjam in my mind over these different proposals.

I attached the pics of inside my attic.

Regarding the thermal insulation, in the attic (which is only technically a crawl space, maybe 3' tall) there is some sprayed cellulose foam and some minimal fiberglass batting. I don't think its all over the place.

In SF we generally have cool temps and mild summers, we have a furnace and no A/C. I've been leaning towards a black roof to minimize our heating costs and because we are never too hot in the house. How does this affect roof lifespan?

1985gt mentioned to cover the roof with gravel. I had leaned against having actual gravel back on the roof as it become almost impossible to inspect. But perhaps with a thick enough coating, it could be more durable than the granulated cap... perhaps I can reuse my old gravel.
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Old 06-11-2013, 02:45 PM   #10
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BTW, house was built in 1942, last roof was done in 1992 at a cost of $5200 (SF building permits)
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Old 06-11-2013, 03:33 PM   #11
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Help evaluating bids for a flat roof in San Francisco


1985gt just gave you my favorite spec for your project. Other than the epdm which I don't understand that roof will give you many years of worry-free use. Of course with any system you choose, it's only as good as the installer. Sounds like none of us are big fans of mineral cap sheets on any roof you expect to last more than ten years.

If you want to see the ferrari of cap sheets, take a look at this. http://www.garlandco.com/products/ro...r-mineral.html

Set in green lock adhesive and you heat weld the laps just like single-ply. Welds smoother and easier than any single-ply. You are never going to get those laps to separate. It's the slickest, cleanest, most bullet-proof roof you've ever seen when finished. I love doing them.

That's the only mineral cap sheets I like using. Nothing beats coal tar on a flat roof...'cept maybe metal.

Last edited by OldNBroken; 06-11-2013 at 03:36 PM.
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Old 06-11-2013, 03:37 PM   #12
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Help evaluating bids for a flat roof in San Francisco


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...Well it took you long enough.
Oh you know I want to make some comment to the effect of "Some of us have better things to do..." But of course I won't.
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Old 06-11-2013, 03:45 PM   #13
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Help evaluating bids for a flat roof in San Francisco


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Originally Posted by OldNBroken View Post
1985gt just gave you my favorite spec for your project. Other than the epdm which I don't understand that roof will give you many years of worry-free use. Of course with any system you choose, it's only as good as the installer. Sounds like none of us are big fans of mineral cap sheets on any roof you expect to last more than ten years.

If you want to see the ferrari of cap sheets, take a look at this. http://www.garlandco.com/products/ro...r-mineral.html

Set in green lock adhesive and you heat weld the laps just like single-ply. Welds smoother and easier than any single-ply. You are never going to get those laps to separate. It's the slickest, cleanest, most bullet-proof roof you've ever seen when finished. I love doing them.

That's the only mineral cap sheets I like using. Nothing beats coal tar on a flat roof...'cept maybe metal.
Im pretty sure 1985 gt is refering to the use of EPDM as secondary protection under the metal coping. Thats what I spec too, in case you have to remove it.
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Old 06-11-2013, 03:51 PM   #14
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Help evaluating bids for a flat roof in San Francisco


The bitumen drippage in your photos is really minimal compared to what I have seen and you will be fine with the spec given you by 1985 gt.
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Old 06-11-2013, 03:57 PM   #15
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Help evaluating bids for a flat roof in San Francisco


I C. So just a slip sheet of sorts.

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