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Old 04-29-2014, 01:18 PM   #1
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Pergola roof top


Hi all,

I am building a free standing pergola that will have a flat 12x12 roof. The roof will be made of 12 2x12x12 redwood boards laid flat (I want maximum shade).

I would like to waterproof this roof so that water doesn't leak between the boards.

I checked online for different solutions for not too visible coverings (I want the covering to be white):
- White IB Membrane: Would be very discrete, would reflect the sun, the problem is that they won't sell the materials to individuals, and you need special tools to connect the seams (Hot air welder) that cannot be rented where I live.
- Corrugated white metal roof
- Corrugated white plastic panels
- TPCM membrane (Any suggestion of a self adhered white membrane?)

So far I think TPCM might be the solution but I haven't found a brand that I can buy in the Bay area (California),

My second choice would be Corrugated white metal roof, but I don't know yet where to buy it.

Any advice would be appreciated.
Thank you,
Regards,
John

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Old 04-29-2014, 02:24 PM   #2
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Pergola roof top


What do you mean by 'flat'? They need to be installed on their edges a spaced out every 16" or so. If you lay them flat and span 12' they will quickly begin to bow or sag.

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Old 04-29-2014, 02:28 PM   #3
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There will be 9 2x6x12 joists laid vertically to support the boards roughly drawn here:



Regards,
John
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Old 04-29-2014, 03:42 PM   #4
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Pergola roof top


Okay that makes sense now. You still may want to consider beefing up the 2x6s. Not sure where you are located, but any snow will create quite a bit of weight causing the whole thing to sag, which may happen anyway over time.

Why not pitch the roof structure and bit or use slats (2x2s) that run perpendicular to the 2x6s...you'd still get quite a bit of coverage, but wouldn't have to worry as much about sagging.
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Old 04-29-2014, 04:30 PM   #5
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Okay that makes sense now. You still may want to consider beefing up the 2x6s. Not sure where you are located, but any snow will create quite a bit of weight causing the whole thing to sag, which may happen anyway over time.

Why not pitch the roof structure and bit or use slats (2x2s) that run perpendicular to the 2x6s...you'd still get quite a bit of coverage, but wouldn't have to worry as much about sagging.
Hi,

I live in California so snow will never be an issue. The problem is that it can get very hot and I have no shade in backyard. This is why I want to cover the entire roof. I am not to worried about the sagging of the 2x12x12 as they are spaced out around 24in appart and nobody will walk on them. Are you saying that I should replace my 2x6s by 2x8s for the joists?

John
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Old 04-29-2014, 05:19 PM   #6
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I would build it and then call local roofing companies and get some quotes. It is really small, cant cost that much to have a roofer come in and do it right.

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Old 04-29-2014, 05:22 PM   #7
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I would build it and then call local roofing companies and get some quotes. It is really small, cant cost that much to have a roofer come in and do it right.

I got a quick quote from an IB roof contractor, they wanted to charge 2000$ for such a small work. (twice the amount of the materials for the entire pergola...)

Putting a roof shouldn't be too hard on a small, flat, square area. Just need to decide what to put to weatherproof it.
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Old 04-29-2014, 05:28 PM   #8
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3-ply mod bit - ideally torch applied. Still need a roofer unless you have a torch.

I think that's the best option, good roof and not that much $.
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Old 04-29-2014, 06:01 PM   #9
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Pergola roof top


http://www.ducan.com/deck-coating/default.php I used something like this on a deck many years ago. I bought it at Meeks lumber yard in Tahoe. I would think you could find it or something like it.

Last edited by Robpo; 04-29-2014 at 06:03 PM.
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Old 04-30-2014, 11:38 AM   #10
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I got a quick quote from an IB roof contractor, they wanted to charge 2000$ for such a small work. (twice the amount of the materials for the entire pergola...)

Putting a roof shouldn't be too hard on a small, flat, square area. Just need to decide what to put to weatherproof it.

Your right us roofers shouldn't charge so much, after all the hot air welders, extremely high priced insurance, trucks, fuel, training, peoples wages, ect.

To be fair 1,333.00 per square is a decent price, especially if they put down a coverboard, installed metal edges and tied in to another roof.

For the self adhered membrane you have to have some slope, plus you are also looking at around $300 for the nail base sheet and cap sheets alone.
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Old 04-30-2014, 11:54 AM   #11
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Your right us roofers shouldn't charge so much, after all the hot air welders, extremely high priced insurance, trucks, fuel, training, peoples wages, ect.

To be fair 1,333.00 per square is a decent price, especially if they put down a coverboard, installed metal edges and tied in to another roof.

For the self adhered membrane you have to have some slope, plus you are also looking at around $300 for the nail base sheet and cap sheets alone.
I understand that for such a small work, the fixed costs like truck, fuel are still there and proportionally bigger. But since I do most things myself in my house (otherwise I would not be able to afford them) this is definitely the kind of job I could do myself.
I watched the IB videos and it doesn't seem complicated to do on a small square surface like mine with no openings (especially knowing that it is a patio cover, not a roof on the house - a leak would be easy to fix later and would have no consequence). The issue is that the tool cannot be rented. It is a shame because IB membranes looked great and for my surface using an online estimator, it was around $200 of materials...

There are things for which I use the help of contractors because I don't want to mess things up (Furnace / AC installation, main roof renovation...) But what I can do myself, I do.

John
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Old 04-30-2014, 12:02 PM   #12
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I understand that for such a small work, the fixed costs like truck, fuel are still there and proportionally bigger. But since I do most things myself in my house (otherwise I would not be able to afford them) this is definitely the kind of job I could do myself.
I watched the IB videos and it doesn't seem complicated to do on a small square surface like mine with no openings (especially knowing that it is a patio cover, not a roof on the house - a leak would be easy to fix later and would have no consequence). The issue is that the tool cannot be rented. It is a shame because IB membranes looked great and for my surface using an online estimator, it was around $200 of materials...

There are things for which I use the help of contractors because I don't want to mess things up (Furnace / AC installation, main roof renovation...) But what I can do myself, I do.

John
So go find your local commercial roofer and ask for a 12'x12' chunk of TPO, or white EPDM. You won't have any hanging over the edges but you could still have them form a drip edge for the area. The thing is while you can glue directly to wood any nail pops go through the membrane. We always put a coverboard. I hope you were planning on gluing it down, you can't just flop it up there and hope it stays, it has to be attached some how. I would call your nearest commercial roofer and ask amount material sales. We do it all the time. I'll give you a roof in a box if that's what you want. Probably make more money doing it then actually installing a roof of that size.
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Old 04-30-2014, 12:15 PM   #13
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So go find your local commercial roofer and ask for a 12'x12' chunk of TPO, or white EPDM. You won't have any hanging over the edges but you could still have them form a drip edge for the area. The thing is while you can glue directly to wood any nail pops go through the membrane. We always put a coverboard. I hope you were planning on gluing it down, you can't just flop it up there and hope it stays, it has to be attached some how. I would call your nearest commercial roofer and ask amount material sales. We do it all the time. I'll give you a roof in a box if that's what you want. Probably make more money doing it then actually installing a roof of that size.
I was planning to put flashing around the edges of the 12x12 surface and glue the membrane directly on top of the boards (the screws holding the 2x12x12 boards will be recessed to avoid damaging the membrane).

Are you saying that I can directly order a white 12ftx12ft EPDM with a drip edge? Do you have a rough idea of the price?

Another idea that I had is to not use 2x12x12 boards + membrane to make the roof but rather to use insulated white corrugated metal sheets. But I could not find a local (San Francisco bay area) distributor yet and I have no idea on how to connected the sheets together in a waterproof way.

Thank you for your help,
Regards,
John
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Old 04-30-2014, 12:42 PM   #14
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Originally Posted by Slashp View Post
I got a quick quote from an IB roof contractor, they wanted to charge 2000$ for such a small work. (twice the amount of the materials for the entire pergola...)

Putting a roof shouldn't be too hard on a small, flat, square area. Just need to decide what to put to weatherproof it.
Yes, I wonder that with the weight of 2x12s laid flat the 2x6's could start to sag. If you're considering roofing the structure, you don't need something as beefy as a 2x12. Just another thought.
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Old 04-30-2014, 01:21 PM   #15
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Originally Posted by Slashp View Post
I was planning to put flashing around the edges of the 12x12 surface and glue the membrane directly on top of the boards (the screws holding the 2x12x12 boards will be recessed to avoid damaging the membrane).

Are you saying that I can directly order a white 12ftx12ft EPDM with a drip edge? Do you have a rough idea of the price?

Another idea that I had is to not use 2x12x12 boards + membrane to make the roof but rather to use insulated white corrugated metal sheets. But I could not find a local (San Francisco bay area) distributor yet and I have no idea on how to connected the sheets together in a waterproof way.

Thank you for your help,
Regards,
John
I guess I never asked why 2x12s? Why not plywood?

Membrane comes on rolls. EPDM comes up to 20' wide and 100 + feet long. TPO that is white the widest roll is 12' (at least from our manufactures). You need some kind of covering over the wood to protect the membrane from getting punctures. Hence the coverboard 1/2" insulation. Then glue the membrane on top of it. Screw down the edge, and then strip the edge in.

Sounding like you may need to do some more research on this before tackling it. To do all this for $200 is just not going to happen. A 100' roll of coverstrip cost US around $200. When I sell it by the foot it's more then $2 a foot. You need 1/2 roll for 48'. So theres more then $100. Plus primer, and cleaner, a gallon of each (more then enough) will be more then $50. You need coverboard so that will be around another $100+, The glue depending on material our cost around $85 for 5 gals. You will need around 1/4-1/2 a bucket, you may get lucky and someone has a half open bucket they will sell so $50.00 for that. Then you need the screws and 3" plates to attach the cover board, I'd probably throw those in since you only need 75 of them. Ops forgot you still need the sheet it's self, another $100. Then you need the metal around $150 for the labor to bend it we use 24 ga prefinshed.

As you can see you are around the $600 mark for materials. That's just off the top of my head, using what little EPDM numbers I have in my head. PVC will be more expensive but it's not an option for you since you don't have the welder. So you ahve EPDM or TPO or the SA modified. Like I said with S/A modified you are at at least $300 for just the rolls, not including anything else. metal and everything else you need will be close to the same amount.

Do some serious research before you do anything. All of the manufactures I'm aware of have details on the web to look at.

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