Roof Mount and Open Beam Ceilings

[albert436]

Hi everyone, I have mentioned this issue in passing before but thought I would just start a thread on the topic.

It is for my mom's house, which has open beam ceilings.

There isn't any drywall up top, just sort of knotty pine type planks.

There is a huge beam in the middle of each room.

I'm wondering if roof mounting is possible, or if there are any particular challenges, or if roof mounting will damage the roof and ceiling.

Or put another way, what is the best way to do this ? I'm thinking if I have some info in advance, then I will be better prepared to discuss this with contractors.

Thanks ! ! !

[Mike90250]

at some time, it's going to need re-roofing, and that would be the time to examine the structure to see how to anchor and if there is enough frame to take the load of PV's.

Other than that, I have no suggestions

[posplayr]

I would add that anything you are missing is not adding any strength other than if you had it (i.e. drywall) the roof might have been designed stronger to support it. In other words the fact it has no drywall is really neither here nor there, what matters is if what is there can hold up the roof as is with a PV load.

[solarix]

Usually on any roof that isn't really old, there is more roof structure above the "open ceiling". You need to figure out if there is a layer of insulation or whatever. Can you tell from the eves how thick the roof is? Sometimes we pull out recessed light fixtures to get a camera peek at what is in a roof.... Skylights and roof vents can be a good source of clues as to what is up there too. Your typical "beam framed", open ceiling is going to have a layer of 24"o.c. framing above with osb or plywood decking on top. The beams are usually just for looks.
Personally, I'm ok with attaching solar just to the roof decking, as long as you use good fasteners. But any building dept is going to insist on fastening to the roof framing. Even with just plank and beam construction, you just screw into the beams and use rails able to handle the span between them. We like the engineered screws sold at HomeDepot called SPAX.

[albert436]

Thanks gentlemen.

Yes two times ago of new roofing insulation was put on top of the roof. It was that stuff which is like styrofoam sandwiched between two sheets of tin foil. OK that's not exactly what it is but that's sort of what it looks like.

The beams are fairly massive and I think they would support the tracks.

I think it would be easy enough to have a structural engineer come out to assess the roof to see if it can support the load, right?

PS New roof put on 2 or 3 years ago.

[J.P.M.]

Get someone who knows about structural design and solar attachments and roofing to advise you. Suit yourself, but building depts. and others who know about such things do not advise or allow simple attachment to roof surfaces for a reason. It's not a good idea.

[albert436]

Thanks JPM that's exactly my concern.

[J.P.M.]

Thanks JPM that's exactly my concern.

You're welcome.

[albert436]

Usually on any roof that isn't really old, there is more roof structure above the "open ceiling". You need to figure out if there is a layer of insulation or whatever. Can you tell from the eves how thick the roof is? Sometimes we pull out recessed light fixtures to get a camera peek at what is in a roof.... Skylights and roof vents can be a good source of clues as to what is up there too. Your typical "beam framed", open ceiling is going to have a layer of 24"o.c. framing above with osb or plywood decking on top. The beams are usually just for looks.
Personally, I'm ok with attaching solar just to the roof decking, as long as you use good fasteners. But any building dept is going to insist on fastening to the roof framing. Even with just plank and beam construction, you just screw into the beams and use rails able to handle the span between them. We like the engineered screws sold at HomeDepot called SPAX.

Thanks solarix, I just got a chance to read through your post a second time and I think I am getting my mind around it. I was looking at those tracks/mounts online and I had a look at the SPAX screws, though I can't tell exactly how those are different from regular lag screws. But as I mentioned the beams in the middle of each room are fairly massive. Is this the roof frame you are talking about, or do you mean also where the roof crosses the outside wall framing structure ?

OK thanks for your help.

[inetdog]

Thanks solarix, I just got a chance to read through your post a second time and I think I am getting my mind around it. I was looking at those tracks/mounts online and I had a look at the SPAX screws, though I can't tell exactly how those are different from regular lag screws. But as I mentioned the beams in the middle of each room are fairly massive. Is this the roof frame you are talking about, or do you mean also where the roof crosses the outside wall framing structure ?

OK thanks for your help.

Regardless of what it looks like on the underside, the pretty much has to be rafters running from the center ridge beam down to the outside walls. The roof sheathing would be on top of them and the ceiling boards would be on the bottom, with the option for putting loose fill or foamed insulation in between.
Your problem is that you cannot see from the bottom or the top where those rafters are located, unless you can detect the nails inside the groove of the tongue and groove boards.
If it is not T&G, look for screws or nails, possibly under filler, in the ceiling boards.

[albert436]

No joists, this is "2 inch" TG.

Edit: I'll be out there tomorrow morning, I'll try to remember to take some pics and post them to show you what it is.

[albert436]

Finally remembered to get the pics when I was out at my mom's house today, woohoo!

Let's see if I can get them uploaded in less that 14 attempts.



kitchen.jpg

[albert436]

momdining.jpg

[albert436]

momliving.jpg

[albert436]

mombed.jpg