Expert: Dan Griffin - 8/11/2009

Question
QUESTION: Hello, I recently began building an enclosed porch/sunroom off of the side of my house.  There was originally a screened in porch on a concrete slab there but I tore it down as it was in bad shape and not big enough for the jacuzzi I want to put inside.  I extended the concrete slab and put in a proper footer 36" deep around the perimeter.  The outside dimensions of the new room are 18'-8" Long by 9'-8" Deep.  It is standard 2x4 wall framing.  It has a "shed" roof style, 5/8 OSB, asphalt shingles.  The new room top plate is standard 8' high, and top of the ridge where the roof connects to the house is about 11' high, so it is just about a 4:12 pitch.  I used 2x6 rafters (which all of the tables I looked at said this was sufficient for my span - 9'8"), 16" OC which are joist hangered into a 2x8 PT header board which is lagged into the house studs & house brick every 16" or so.  I used 1/2 x 5-1/2" galvanized lags.  At the sunroom wall the rafters have birdsmouth's cut, are toenailed into the top plate and I also used a Simpson H-1 Hurricane tie on each rafter.  Now for my question:  Originally I was going to run ceiling joists from my top plate of the new wall to the house however I REALLY screwed up.  There are 3 windows on the house wall which will now be inside the sunroom and they are slightly higher than 8', so if I were to run ceiling joists they would go right into the glass if you get what I'm saying.  I am wondering if It is OK to have an open ceiling and just drywall over the rafters.  Do I need ceiling joists for structural purposes since this is a shed roof and not a gable?  I am worried about the extra stress of not having ceiling joists and extra dead load of the drywall on the rafters and am wondering if I undersized them for this application?  The other thing I was thinking about doing was putting collar ties about 2/3 the way up the rafters and attach them to the house with joist hangers.  That way I would have a sloped and then flat area on the ceiling.  I was planning on using 2x4's for this as it's only a 3' span.  I don't know if this would help structurally or not, and then there's the downside of adding the extra dead load of the 2x4's onto the rafters (although I know it would be minimal).  The only other solution I have is to tear out the 3 windows and lower them so that I can run the ceiling joists, although I'd really like that tall ceiling.  I think I covered all of the info you might need.  Any help would be greatly appreciated as I'm at a dead hault until I figure out what to do.

Thanks!

ANSWER: Mike, the 2x6 are ok.  YOu can  hang sheetrock on the bottom of what you have.  The problem is that you don't get much insulation and little or no venting of the "attic" space.  It sounds as if you have fastened the ledger to YOur brick veneer, not an ideal installation and prone to flashing and moisture problems.  If you are confident that your ledger is well fastened to the framing and not pressuring the veneer you may be all right.

YOu don't tell your location or climate.  I think I would create soffit venting and deepen the joists to use 6" insulation with venting in each bay that leads to a vented attic created by your collar tie idea.

Have you had an inspector look at this?

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QUESTION: Dan, thanks for your reply.  I've been doing alot of research and came to the same conclusion about the 2x6's - thanks for confirming.  The ledger (2x8 pressure treated) isn't mounted to brick veneer, it spans across the original house (which is solid brick) and an addition (which is wood framing).  The solid brick span is about 6 feet and I used 1/2"x5 galvanized lags into 3" lag sleeves.  Used the same type of lags into the wood framing framing, 1 into each stud in a staggered formation.  I'm also studding that wall so that I can drywall over.  Was planning on laying 2x4's flat against the house and nailing them to the existing house studs.  They will run all the way up to the bottom of the ledger, so in a sense, it physically have something under it and not just be relying on the lags.

I'm in southeast PA, snow load here is 30psf.  I was planning on having open soffit, using R13 so it will give me a 2" air gap between the insulation and roof sheathing - in the collar tie area there will be approx a foot of open air above.

Got a permit, but no inspection required because it's classified as an enclosed porch, and there was already a structure there - and I've asked the township twice about inspection to be sure.  My township's really laxed about that stuff.  To be honest, I kind of wish there was one required, for piece of mind, but then I think about the original structure I just tore down - The ledger for that was a 1x6 nailed into the house with literally 10 nails.  Rafters were toenailed in with 2 nails each, at the eaves no birdsmouths, no hurricane ties.

ANSWER: Sounds like you're in good shape.  It always amazes me how some old things ever did hang together, of course, some didn't.  I had a small porch that I wanted to come down, had to take it apart a piece at a time as it wouldn't fall.

---------- FOLLOW-UP ----------

QUESTION: Dan, thanks for your response.  I don't want to be a nucance, but I have 3 more questions and then I think I'm good.

1) I'm going to put the collar ties onto the rafters so I have a flat section on the ceiling. The roof is only a 4:12 pitch. and I'm wondering how long the collar ties should extend against the rafters.  Please see this pic:

http://i629.photobucket.com/albums/uu14/mpildis/collartie.jpg

I was thinking about making them 48" long so I get 2 of them out of an 8' 2x4.  That would give me a 16" against the rafter from the first point of intersection.  If I make them 52" long, they would stop right where they hit the roof plywood.  Making them longer than that and having to cut the roof angle on them would be a real pain and seems excessively long to me.  Does 3 10D nails staggered per collar ties sound sufficient?

2) Should I place little studs between each rafter at the half-way point to keep them from twisting since it's going to be an open rafter ceiling?

3) The rafters are toenailed into the top plate and have simpson h2 hurricane ties on the outside wall.  Since it is going to be an open rafter ceiling, should I place hurricane ties on the inside wall as well or is this overkill?

Thanks!

-Mike

Answer
Mike,
1.  Square cut the collar ties, they'll be fine.  10d nails will work, especially if you have them - I wouldn't bother buying them if you already have 16's.

2. I don't think you'll have twisting problems if you get them in and get them nailed.  Sunshine seems to be the primary cause of twisting boards and you're already in the dry.

3.  Many buildings have been up for generations before God or Simpson invented rafter ties.  Some builings lost roofs in high winds.  I wouldn't worry about it if you got a good bite with your toenails.  If things are iffy the tie downs are relaively cheap.  Yes, overkill.