Roof mounting a small solar panel without screwing into the roof using silicone

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timmmay

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#208082 26-Jan-2017 07:35

I have a single 40W solar panel that I'd like to mount to my shed's corrugated iron roof without drilling holes in the roof. Reason is I don't want to create a leak and I'm only ok at DIY. I could pay someone, but that's not the kiwi way.

The place I bought my solar panel said I could bolt the panel onto some 2cm thick wood rails, then silicone the wood to the roof. The wood is to create a small air gap, to keep the panel cool. I think he suggested attaching the wood down the long side of the panel, leaving only the shorter top and bottom open, to reduce wind going through but still giving enough cooling. This is in Wellington, which you may be aware gets some wind.

An alternate approach is these brackets, made for caravans, which do appear to regularly be attached with silicone. Caravans aren't corrugated though.

Does this sound reasonable to anyone? Is silicone strong enough to hold a solar panel to a roof in Wellington reliably? If it comes off it in a storm could really hurt someone, probably me.

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wellygary

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#1709738 26-Jan-2017 07:59

NO!, do not use silicon to hold a 3Kg panel to a corrugated roof in Wellington, the corrugations will mean tha actual contact area with the roof is very small...

Just screw it on, if you screw into the "high" parts of the corrugated iron and through to the purlin below and then apply silicon to the holes you will be fine, rain goes down the "low" parts of the corrugations

If you are wanting to use a price of wood to increase airflow, thats fine, but again screw right through it and the panel to the roof below....

Cody64

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#1709739 26-Jan-2017 08:02

Can you use brackets that can be screwed down by removing some of the existing nails then use sealer and long tek screws in their place? As the screws are on top of the corrugations there is less chance of leakage.

timmmay

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#1709743 26-Jan-2017 08:18

Ok, sounds like I'll have to actually screw it on if I want it outside. Right now it sits inside the shed in the window, gathering only a little bit of sun. I might have to get mounts and have someone else mount it to roof for me - I think I know a guy who can do that.

MikeAqua

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#1709753 26-Jan-2017 08:43

Regular silicon is more of a sealant than an adhesive. Modified silicon is a bit more adhesive.

3M make a product called 5200. It will hold just about anything to just about anything. It's also often used as a gasket between two materials that are screwed together to avoid point loading.

I would be slightly concerned about only using screws for your solar panel.

Roofing steel is quite thin, so generally you only have 1 - 2 threads gripping it. It's easy for a screw to gradually rock out over time. At the very least you would want screws with wide threads and plenty of them.

Ideally you would use roofing 'tek' screws and fix into the purloins underneath the roofing steel. They have excellent holding power. That's how the professionals installed the brackets for our solar water.

Mike

timmmay

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#1709755 26-Jan-2017 08:50

That kind of product is more what I'm talking about I think, a silicone based adhesive. But it could put a lot of load onto the paint that's on top of the roofing iron.

Sounds like the best option might be to use some spare roofing screws to screw some metal rails or feet to the roof, then use some kind of bolt system to attach those to the panel. Like these.

tieke

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#1709805 26-Jan-2017 09:32

I attached a small panel to a corrugated roof by attaching some pieces of wood onto the roof for the top and bottom of the panel. I also didn't want to make any new holes, so just unscrewed two existing roof screws for the end of each bit of wood and then rescrewed these through the top of the wood with rubber washers underneath. I countersunk the holes so that the screws wouldn't poke out, and also drilled holes through the wood so that it could sit flush over the in-between roof screws.

timmmay

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#1709809 26-Jan-2017 09:37

Would I need longer / wider screws if I take existing screws out and want them to go through 1-2cm of wood? Otherwise the screws won't go down as far as they did before and may not bite into good solid wood.

Sounds like a pretty good compromise solution. I could also use some of those metal brackets in the current holes, if they line up properly, which seems unlikely.

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richms

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#1709812 26-Jan-2017 09:43

The normal way to install panels is to put rails across the outside over where the wood is, and then the panels are held onto those with holddown clamps. Looks expensive for just 1 panel to go to all that effort. I would see if some L brackets would line up with the roof screws and the side of the panel at all.

Richard rich.ms

timmmay

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#1709818 26-Jan-2017 09:45

I guess I could attach the Z brackets to the roof wherever suits, then screw into the panel frame wherever I like. Should be easy enough actually.

SCUBADOO

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#1709844 26-Jan-2017 10:08

Don't use silicon!

FWIW

No screw or rivets involved. (-;

I have 2 x 300W 23kg solar panels mounted on the fibreglass roof of our motorhome on 6 aluminium right angle 250mm brackets made from 50x50x3mm extrusion.
They are attached with Sikaflex 11FC sealant/adhesive.
Allow an air gap between your roof and the panels to improve output in hot weather.

2 years later, 40000km and frequent 100km/h speeds. They are still there and operating perfectly.

blakamin

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#1711303 29-Jan-2017 13:09

We used an industrial version of this from bunnings for holding ACM to sign frames and trailers. Your panel would go nowhere.

Edit: What the post above mine said, basically, but with a link.

Besides the rivets holding the checker-plate on, those big panels are held on with the same type of stuff... this is a racing car trailer.

timmmay

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#1711306 29-Jan-2017 13:15

I might use the Z brackets with the existing roofing screws anyway, with the panels bolted on. Seems like the easiest way. If I'm feeling paranoid I might put some of that onto each side of the Z bracket, but then getting it off could be next to impossible.

blakamin

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#1711308 29-Jan-2017 13:27

You can cut it with a razor blade.

SCUBADOO

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#1711328 29-Jan-2017 14:29

Piano wire works well also.