roof load increase?

System · January 2012

Hello,

I am considering having a pole barn built. On top of the barn I would like to put solar panels. I will either do it myself or find an energy company to lease the space.

Do I have to worry about having the roof beefed up to a certain load for panels to be safely installed?

Thanks in advance.

BB. · January 2012

Re: roof load increase?

In most areas of the US, you will need a civil engineer to sign off your plans--So, you might want to check with your current designer/engineer and see if they can give you more information.

-Bill

System2 · January 2012

Re: roof load increase?

rather than speak to an engineer who rarely would deal with this, I thought I would ask people who probably have more experience with this. or at least I thought they should.

solarvic · January 2012

Re: roof load increase?

it depends on what your local building codes are. In Pa. you have to have everything inspected before power company will let you connect. Lots of red tape. solarvic

westbranch · January 2012

Re: roof load increase?

leon phelps wrote: »

I will ..... find an energy company to lease the space.

Do I have to worry about ?

If you plan on leasing the space and the barn collapses, who do you think will be taken to court? the P.Eng. that signed off the plans, if it designed /reviewed ..... otherwise it is You...

BB. · January 2012

Re: roof load increase?

Building codes can be very location specific... You may have snow loads, Florida has wind loads, I have earthquake loads.

For the most part, solar arrays are not that heavy and "most" structures should be able to support a simple array. The bigger issue is usually the mounts, straps, and fasteners.

You should also talk with your "roofer"--They probably have better information as to which roof material and what mounting/flashing system will work best for you (many roofers I have spoken with spend a fair amount of time fixing leaking roofs for electrical contractors after they have installed the array--One roofer I used is looking into installing solar himself since he is already doing a lot of the roofing work).

-Bill

solarix · January 2012

Re: roof load increase?

Roof loading due to Solar PV is about 3lbs / sqft. which is not that much and there are rarely any roof failures due to solar.
However, few if any roofs were originally designed with solar in mind and getting a system permitted means adding this unintended load to your roof which means any building department will want independent analysis that the roof will be adequate. I've been in this same situation and take my word for it, start with having a local PE look at your structure.

SolaRevolution · March 2012

Re: roof load increase?

In Mendocino county, CA the building department almost always requires structural engineering for roof mounts.
In Sonoma County, CA (next county south) they almost never do.

Here is a install of Mitsubishis on a barn roof which came out to 2.91 lbs/sqft
Attachment not found.
I've found that doing a data sheet like this for your plans can either get you through the building department faster or save hours ($$$) on your structural engineering bill.
Attachment not found.

niel · March 2012

Re: roof load increase?

actually, in most cases the extra weight isn't the problem as roofs are under high stresses normally from high winds and snow loads pushing down on the roof structure even though i acknowledge it does need to be factored. the real problem most roofs are presented with when going to pvs is the lift the pvs can give when high winds hit them just right. many roofs don't handle high lifting forces well as is seen by tornado and hurricane damaged homes.

solar_dave · March 2012

Re: roof load increase?

It is pretty crazy here, Most newer roofs are trusses, with weight load designed to take Concrete Tiles for the roofing components. That means they are overengineered to begin with but when adding solar a structural engineer must sign off. 2 code reviews are done on site, structural and electrical.

westbranch · March 2012

Re: roof load increase?

don't know what the rules are down South, but here in BC you can renew your roof by just placing a second layer of asphalt shingles over the previous one ( Once) then you have to strip it all off for layer #3... so figure out how much a layer of roofing weights, bundle of shingles =~ 33 sq. ft and weighs ~ 80 pounds...

roof load increase?

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