reenforcing roof trusses

[Mike 134]

This is a question to those that have done multiple installs. Have you had to do any reinforcement of the existing roof trusses before adding the new panels and framing?

[Ampster]

This is a question to those that have done multiple installs. Have you had to do any reinforcement of the existing roof trusses before adding the new panels and framing?

I have had solar installed on four homes in California. Only one had roof trusses and the installer did not have to do any reinforcement. The other installs were traditional framing and I pulled two of the permits myself. The calculations were all about uplift since the weight of the panels was insignificant for my structures. In the designs I had control over I wanted to reduce penetrations so in those cases I used heavier rail that was able to have longer spans and I never encountered a situation where the framing members had to be reinforced. In those cases the roof rafters were at least 2x10 on 16 inch centers with spans of no more than 20 feet.

With trusses typically constructed of 2x4 on 24 inch centers I can imagine the engineering would in some cases require some additional reinforcement. I think a lot depends on wind and snow loads and other local jurisdiction requirements, In all my situations, snow and wind loads were not factors.
Are you adding new framing?

[PVAndy]

This is a question to those that have done multiple installs. Have you had to do any reinforcement of the existing roof trusses before adding the new panels and framing?

We have to do reinforcements in about 1 of 10 installs

[foggysail]

We have to do reinforcements in about 1 of 10 installs

Would you elaborate? I am trying to get a better understanding of an install because I am going to try doing my own----if I can get the permits.

Sure, I understand the structural advantage of trusses but not all homes here in Massachusetts have them. The reason for my question is asphalt shingles are HEAVY and code allows two layers. NOw I am not advocating installing panels ontop of two shingle layers, I only mentioned two shingle layers to show modern roofs should be able to carry a panel load. Consider 440 watt panels, one installed above the other with each having a weight of about 50 pounds each for a total of 100 of course for a vertical pair. But the widths of the panels are unimportant in my analysis because they are supported by a rail system. So the weight problem as I see it can be distributed by judicious placement of the rail supports.

Even with a good understanding, it will do me little good because I will be forced to get a structural engineer's report before I can get a permit. Thanks for taking the time to even read my post if you get this far.

[foggysail]

I have had solar installed on four homes in California. Only one had roof trusses and the installer did not have to do any reinforcement. The other installs were traditional framing and I pulled two of the permits myself. The calculations were all about uplift since the weight of the panels was insignificant for my structures. In the designs I had control over I wanted to reduce penetrations so in those cases I used heavier rail that was able to have longer spans and I never encountered a situation where the framing members had to be reinforced. In those cases the roof rafters were at least 2x10 on 16 inch centers with spans of no more than 20 feet.

With trusses typically constructed of 2x4 on 24 inch centers I can imagine the engineering would in some cases require some additional reinforcement. I think a lot depends on wind and snow loads and other local jurisdiction requirements, In all my situations, snow and wind loads were not factors.
Are you adding new framing?

Ampster--- Most of California is relatively warm so most likely there were no snow loading worries..... is this correct for those installations you mentioned? Thx

[Mike 134]

Would you elaborate? I am trying to get a better understanding of an install because I am going to try doing my own----if I can get the permits.

Sure, I understand the structural advantage of trusses but not all homes here in Massachusetts have them. The reason for my question is asphalt shingles are HEAVY and code allows two layers. NOw I am not advocating installing panels ontop of two shingle layers, I only mentioned two shingle layers to show modern roofs should be able to carry a panel load. Consider 440 watt panels, one installed above the other with each having a weight of about 50 pounds each for a total of 100 of course for a vertical pair. But the widths of the panels are unimportant in my analysis because they are supported by a rail system. So the weight problem as I see it can be distributed by judicious placement of the rail supports.

Even with a good understanding, it will do me little good because I will be forced to get a structural engineer's report before I can get a permit. Thanks for taking the time to even read my post if you get this far.

I'm like you wanting to do a DIY solar install and it's been a learning experience. I likely have an advantage because of being a retired licensed electrician I'm well aware what a PITA the permitting process can be.
You need to be sure to find a structure engineer that is up to speed on the building code calculations in regard to solar panels and how it effects snow loads on a sloped roof. (I found not all are) Also the elimination of live loads under the solar panels. The first guy I talked with doing just some "out loud thinking" thought I'd need to buy about $1600 in additional lumber to reinforce the truss roof. Add to that his cost for stamped drawings and the labor to add the additional framing. Fortunately I found a guy who specializes in solar installs so I ended up not needing any new framing and he was well aware of all the little details found in the most recent building codes. He pointed out you need to stagger your point loads to as many framing members as you can because that is what is carrying all the weight of the panels and mounting system on the roof. You don't want one rafter having 4 mounts on it while the one next to it has none.

Have you used the Iron Ridge design tool? Makes it really easy to design your mounting system. Gives you all the load calculations I should add I'm near Chicago so have 30PSI ground snow load and the new ASCE7-16 wind code of 107 MPH for uplift

[J.P.M.]

Ampster--- Most of California is relatively warm so most likely there were no snow loading worries..... is this correct for those installations you mentioned? Thx

If local codes are followed, which, in the U.S. anyway, mostly follow and take guidance from ASCE 7-16 et seq. and will account for all expected or code mandated external loadings as well as the expected or design for combinations of those external loads.

[Ampster]

Ampster--- Most of California is relatively warm so most likely there were no snow loading worries..... is this correct for those installations you mentioned? Thx

All I can tell you about the two installations I did in California was that it was uplift caused by wind which was the biggest factor. That determine the depth and number of fasteners. I am not an engineer but relied on the engineering calculations by the racking companies.

[foggysail]

THANKS GUYS!!!!

Mike--- I am also retired, have a BSEE that I needed for electronic circuit design and Massachusetts journeymen & master electrician license that I let expire in 2016. Had the licenses before going for my degree in my 30's. After leaving engineering I teamed with a friend to build 4 homes and reconstruct old tenement buildings in Rhode Island. Partner is gone, new homes gone but I retain the LLC and 10 of the 19 apartment units. Had over 15 guys working for us at one time.

GREAT FORUM for sharing, important needed knowledge!

J.P.M.----I will follow your suggestion and get a copy of ASCE 7-16 et seq.

Ampster---WIND! I had no clue that wind could be a problem but of course.............it can be! I will also look into racking.

Wifey is adamantly against solar, I am working on that problem as well! But our Governor Baker fell in love with sola and is sticking it to the electric companies such as Eversource who is now sticking it to their customers. Sure, the electric cost is reasonable, mine is 12 cents/KWH but distribution is 15 cents for a total cost of 27 cents/KWH and about to soar. The electric producers must increase renewable's use by 3% a year and I just received a notice from Eversource for a cost adjustment starting next year. The progressives are making life expensive for everybody but that is a different topic and not suited for this forum.

Thanks again everybody, I will be back with more questions as my quest for solar continues

Foggy

[J.P.M.]

THANKS GUYS!!!!

Mike--- I am also retired, have a BSEE that I needed for electronic circuit design and Massachusetts journeymen & master electrician license that I let expire in 2016. Had the licenses before going for my degree in my 30's. After leaving engineering I teamed with a friend to build 4 homes and reconstruct old tenement buildings in Rhode Island. Partner is gone, new homes gone but I retain the LLC and 10 of the 19 apartment units. Had over 15 guys working for us at one time.

GREAT FORUM for sharing, important needed knowledge!

J.P.M.----I will follow your suggestion and get a copy of ASCE 7-16 et seq.

Ampster---WIND! I had no clue that wind could be a problem but of course.............it can be! I will also look into racking.

Wifey is adamantly against solar, I am working on that problem as well! But our Governor Baker fell in love with sola and is sticking it to the electric companies such as Eversource who is now sticking it to their customers. Sure, the electric cost is reasonable, mine is 12 cents/KWH but distribution is 15 cents for a total cost of 27 cents/KWH and about to soar. The electric producers must increase renewable's use by 3% a year and I just received a notice from Eversource for a cost adjustment starting next year. The progressives are making life expensive for everybody but that is a different topic and not suited for this forum.

Thanks again everybody, I will be back with more questions as my quest for solar continues

Foggy

You can get a copy of ASCE 7-16 but it'll set you back $240. For solar array external loads (of which wind is only one) for both structure and ground mounted, there are other non official but still useful guides that can be as good for ASCE 7-16 compliance, but only as a primer for compliance with that code. The code will govern in all cases. Many such discussions, meeting minutes and tutorials are on line.

ASCE 7-16 will only specify which loads are to be considered, in what ways they are applied to a structure, and their required combination(s). ASCE 7-16 will not tell you much about actual design methods to meet those loads.

BTW: The best way to hold down increasing electric bills is via use reduction and conservation. A good way to have some control over energy destiny. Also, for those with a woody for power companies, it's also a good way to get back at the POCOs.

What's making life expensive isn't the solar tree huggers, it's people's profligate use of electricity.

[foggysail]

Yes! I did look at ASCE.... multiple $$ books. Heck, I already talked to my town's building inspector who is going to require an engineering drawing which means I will need to pay for engineering. In the meantime I am searching and gathering as much info as I can. Also spoke with the town's electrical inspector. He told me that If I can get the building permit, he will allow me to pull an electrical permit.

I want to be as knowledgeable as possible before starting. I have to wait anyway until around August to get my bucks together. I had them until a family emergency swallowed most of them. I want this to be a cash event. Without an analysis, my guess is the roof should be OK. It is just short of 30 degrees (28.8) with 2x8 rafters 16'' on center with a single layer of asphalt shingles.

As to the cost of electricity, my comments here are not intended to start an argument....... There are more important things in life than punishing the entire country to be green. And today's WSJ has an excellent article ''Be Afraid of Nuclear WAR, Not Climate Change!'' that I firmly am concerned about. Another thing we should be concerned about is also discussed in their Opinion section which is America's Declining Military.

[Mike90250]

how old are your existing asphalt shingles ? Maybe consider replacing them before you clutter the roof up

[foggysail]

They are about 6 years old Mike. But at my age now, I doubt I will outlast their life. Someone else can worry then. And I did make a mistake when I had the re-roofing done!!! I wish I had gone with a steel replacement rather than asphalt shingles.

[bcroe]

I did make a mistake when I had the re-roofing done!!! I wish I had gone with a steel replacement rather than asphalt shingles.

Metal roofs have issues too. 3 buildings with them here. Some styles are
extremely slippery, need special shoes, not possible when wet. I have
antennas up there, will need to construct a safety rail on house to hook onto,
traction strips near antenna mounts. Wire guides will need to bolt onto seams.
Penetrations should be avoided. More on that in a year.

My panels are ground mounted. Bruce Roe

[peakbagger]

BTW, in Mass you either pay to put solar on your roof or pay (via your bills) for your neighbor. That now incluces having a home battery. Even if the supply side stays flat, distribution is going to keep increasing to pay for increased RPS percentages an incentives for Clan Peak and other battery incentives. I thank all Mass ratepayers for paying for my salary for last 8 years building Combined Heat and Power plants that were awarded large front end and ongoing incentives. The only way to win is not to play and that means moving out of state or installing renewables and batteries.