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Old 03-04-2013, 12:24 AM   #1
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BUR - sealing pilot holes


Hello,

I am looking at installing a solar PV system. There will be about 20 mounting points.
The roof is a BUR (tar and gravel) with 2:12 (9 deg) slope.

It consists of 3 or 4 ply on top of 2" tongue and groove paneling on top of 4x6" girders.

The stainless steel hanger bolts will be 3/8" and the pilot hole will be 11/32". They will go through the 2" paneling and will be embedded 3" into the girders.

What type (or even brand) of sealant should the (cleaned) pilot holes be filled with before inserting the hanger bolts?

Thanks

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Old 03-04-2013, 06:14 AM   #2
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BUR - sealing pilot holes


Well, it's a bit more complicated than that. You really need some type of pitch pockets. To improve on that, a SS frame should be mounted using pitch pockets and the solar panels mounted to that grid.
That's assuming the roof is new, or nearly so. If the roof is fairly old, or just brittle and 'worn', you're opening a huge can of worms so far as it's longevity and water tightness goes.

You should have a professional that does BUR co-ordinate with the solar company to design and install a proper grid. As a side note, I'm hearing of roof damage from overheating when the panels aren't raised far enough above the roof. I haven't confirmed that's a cause of failure yet, but if I'm the winning bidder, I'll know more when we get the panels removed.

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Old 03-04-2013, 07:56 AM   #3
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BUR - sealing pilot holes


You start out by saying you are going to need 20 mounts installed on a BUR. Then you go on to call them "Hangers" Hangers hang, mounting posts mount above, which is it?

You cannot use sealant unless you want it to leak like a seive. You should not use pitch pockets, they are an invitation to leaks. You want to use pipe stands, with a mounting plate welded to the top, and unistrut between pipes on which to mount your panels. Limit your penetration as much as possible.Your pipe should be 3 inch schedule 40 steel, and should extend and attach to the structure below. You need to remove the gravel surfacing where the hole for the pipe will penetrate for about 2 feet square. Once the pipe penetrates the membrane, wire brush and prime the spudded area with D-41 Primer (I am assuming an asphalt roof, if your roof is Coal Tar Pitch you must use pitch based cement. Using a lead pipe flashing coat both sides of the base flange with D-41 and let dry. Trowel Modified flashing cement over spudded area, then set pipe jack down into modified flashing cement, and work into place. Coat top of flange and roof with Modified roof cement, then install Modified Bitumen target that extends 6 inches past lead flange onto spudded area. Coat edge of tie in with cement 8 inches wide centered on edge of target patch and embed 6 inch asphalt saturated fabric in modified cement. Top coat with cement, Wrap top of lead pipe jack with 6 inch uncured EPDM quickseam flashing.
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Old 03-04-2013, 10:22 PM   #4
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BUR - sealing pilot holes


Sorry for the lack of information.

The roof is not new but still has 10 yrs left (according to an inspector).
There will be a grid installed on which the panels will be mounted. The hanger bolts I mentioned will serve as mounting points for the grid (racking).

And yes, they are hanger bolts, but special stainless steel hanger bolts for mounting of solar racking.

I did some more research and found this product. This seems to be perfect to seal off the penetrations:

http://www.chemlink.com/content/inde...=82&Itemid=226
http://www.bigrocksupply.com/store/p...iCurb-Kit.html


What do you think?

Thanks!
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Old 03-05-2013, 09:08 AM   #5
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BUR - sealing pilot holes


According to what inspector?

Most people, including government agencies forget that all roofs fail in time. When they fail they have to be replaced. About a month ago I looked at the roof of a major government department. They were just about finished installing a solar array on a roof of about 80,000 square feet. The roof that they installed the array on was a fifteen year old modified bitumen. They listened to a representative from one of the scheister companies that always seem to have their home office in Ohio, and coated the roof with a white acrylic coating. I sat at a conference table where 6 engineers constantly called the coating a new roof. Every time they said new roof, I said coating. After a while they got tired of this and said. "We have a 10 year warranty on that coating." I said "Thats great, so when it fails in a couple of years you will have a nice white leaky roof, and ABC company will give you a new bucket of white stuff. In the meantime, you have a leaky roof that you cant get to because you have 60,000 square feet of solar panels covering it." On this roof, they used brackets that set on the roof membrane and concrete blocks were placed in the brackets for ballast. Needless to say, I was considered persona non grata, because I tried to talk common sense. Having lived in the golden triangle since 86, I have learned that government agencies do not like common sense, and they really don't like someone who does not go with the company line. At 66, I go by experience, not warranties spouted by someone wearing a pin striped suit. You can't take a roof cut in a pin striped suit.

My point here is that all roofs fail. The roof membrane is just that. A roof membrane. It is not a platform for solar panels, but people seem to think that it is.

You can put solar panels on a low slope roof, but if you disregard all that we have learned in the last 200 years or so about low slope roofing, you are going to be sorry.

The NRCA has minimum recommended clearances for rooftop mounted equipment. This is generally not being followed by any current solar designs.

The NRCA states that loads imposed by rooftop equipment must be transferred to the structure via structural members, not the roof membrane. This is generally not being followed by any current solar designs.

The result of this is going to be astronomical cost to replace roofs that have failed below the solar arrays that are now being haphazardly installed on very large government installations, and we the taxpayers are going to foot the bill for the ignorance of the people that are in charge of these projects.

You would be wise to consider what I have said here, and think about what you are doing. If you penetrate the roof, patch it like I said, and keep in mind that you have wind uplift to contend with as well ad dead load.
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Old 03-05-2013, 10:14 AM   #6
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BUR - sealing pilot holes


Quote:
Originally Posted by jagans View Post
According to what inspector?
It was one of the inspectors that come out to do the inspection as part of the purchase of a house. He was specialized for roofs. The guy seemed to be experienced.

Quote:
Originally Posted by jagans View Post
You can put solar panels on a low slope roof, but if you disregard all that we have learned in the last 200 years or so about low slope roofing, you are going to be sorry.
Are you saying I should not put a PV system on the roof, period?

Quote:
Originally Posted by jagans View Post
The NRCA has minimum recommended clearances for rooftop mounted equipment. This is generally not being followed by any current solar designs.
Could you help me in determining what this minimum distance would be for my type of roof?

Quote:
Originally Posted by jagans View Post
The NRCA states that loads imposed by rooftop equipment must be transferred to the structure via structural members, not the roof membrane. This is generally not being followed by any current solar designs.
This is exactly why I want to go with the design I mentioned above. The hanger bolts will go through the membrane into my structural 4x6" roof girders". I want no load on the roof surface.
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Old 03-05-2013, 04:44 PM   #7
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BUR - sealing pilot holes


Quote:
Originally Posted by Jaxx View Post
It was one of the inspectors that come out to do the inspection as part of the purchase of a house. He was specialized for roofs. The guy seemed to be experienced.

If he did not take a roof cut, or perform a non-destructive roof survey using an appropriate method like infrared, capacitance, or nuclear, he would be limited to a visual survey only. This can be hit or miss, although a lot can be gleaned by observing the roof surface for general appearance. Generally speaking, the level of knowledge of the average home inspector regarding steep roofs is limited. Regarding low slope roofs it is generally non existent, but you may have gotten the rare exception. If your roof is gravel surfaced he could not see the lap lines, and could therefore not comment on the number of plies, yet you say the roof is a 3 or 4 ply roof. There can be a significant difference in the life of a roof going from 3 to 4 plies, so it is important to know to make an assessment regarding lifespan.

Are you saying I should not put a PV system on the roof, period?

If you have the land, you should build a framework on the ground, and mount your panels there. This way you can easily service them and you don't run the risk of falling.

Could you help me in determining what this minimum distance would be for my type of roof?

The distance from the roof is based on the square footage area that is covered by the roof mounted equipment, but more importantly, it is based on how much room you need to get under the equipment should the roof membrane need to be repaired, or replaced.


This is exactly why I want to go with the design I mentioned above. The hanger bolts will go through the membrane into my structural 4x6" roof girders". I want no load on the roof surface.
"Hanger Bolts" is confusing. You cant mount much of anything on threaded rod that protrudes above the surface of the roof, if thats what you mean, as there is little to no resistance against lateral forces due to lack of cross section. "Hang" means suspended from above. You can hang a ton on 1/2 inch all thread, try setting a ton on top of threaded rod, it will bend like a wet noodle. You cannot properly flash a threaded rod (Hanger Bolt?). The only thing you can do is install a pitch pocket, and fill it with pourable sealer, and they are a leak looking for a place to happen.
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Last edited by jagans; 03-05-2013 at 04:47 PM.
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Old 03-05-2013, 07:19 PM   #8
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BUR - sealing pilot holes


We usually tear off the section of roof where the PV is going. The solar company comes in and mounts thier stand offs...no rails or panels. We then come back in and install the appropriate roofing material around all the stand offs and the rest of the roof area... then the solar folks come in and install the rails and panels.

I wouldnt put solar on a roof that only has 10yrs left (that 10yrs was a based on a visual inspection as noted by Jagans).

The solar stand off typically get lag bolted through the sheathing and into the rafter. Hangers are not something i am familair with, it has always been some type of deck mounted pipe sytem with lags into the framing members. We then treat the pipe as a regular roof jack and flash it accordingly.

http://www.civicsolar.com/sites/defa...ources/web.jpg

the link shows a similar situation to what i think jagans is refering to. The ability to conduct roof maintenance or repairs around the PV panels. These are at least tilted and provide some access...a little tight at the bottom though.
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Old 03-05-2013, 08:00 PM   #9
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BUR - sealing pilot holes


I do not have enough room to mount them on the ground. The roof is the only option I have. I will use a racking system that allows easy removal of panels to access the area underneath.

Quote:
Originally Posted by tinner666 View Post
As a side note, I'm hearing of roof damage from overheating when the panels aren't raised far enough above the roof.
Could you help me determine a recommended minimum standoff to ensure there will be no damage caused by heat? Are we talking 5-6" or much more. I know some people mount them very low (e.g. 3"), I certainly want to stay away further.

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