I need you construction types to lend me your opinions. I'm in the planning stages of a complete outdoor deck revamp to accompany our exterior house makeover. The rotten wooden deck is being replaced by a poured concrete / flagstone patio. Part of the plan is an outdoor structure to act as a grilling and cooking area and a hangout around the wood stove in the winter.
I plan to have all the Concrete handled professionally and I'll build the structure. I want you guys to check my plans, specifically the spans and lumber selection. Here's my initial sketches.
what we have here is a 12'x12' structure with open sides and a roof. Posts are 6x6 and are 10' on one side and 7' on the other to give a roughly 3/12 pitch flat roof. The headers are 2x10s that are doubled and mortised into the post tops. 4x4 knee braces kick off the posts and come up between the header boards. Rafters will be 2x8s on 16" centers to carry the 12' span with 2x4 purlins and corrugated tin. Rafters will tie to headers with metal ties. All wood is treated. Posts are sunk in ground with concrete. Central Georgia, so no snow load to speak of but tropical storm level storms occasionally.
my main concerns -
- will 2x10s doubled this way be enough to carry the weight and allow for the 48" free span on one side? I could drop a center post instead of knee braces but I'd rather not.
- are 2x8s enough to carry the roof span?
After sleeping on this idea, I think making a 2x10 beam out of two boards glued and screwed together might be easier than the spaced beam and mortise cut posts. That would mean one cut per post instead of 2.
any thoughts?
Just bumping this back to the top since some of our construction minded members are around
2X10s glued-screwed together is overkill for the weight it will carry, your call. 2X6s glued with 3/8" ply in between makes a lambeam set up, sturdier. I used 2X12s when I jacked up the upstairs of my house! (of course supported from the basement and up through the walls) More span requires more depth of wood, use 12 or 14 not 8 or 10s, load bearing is in the bottom of the board I'm told.
I would knee brace all 8 corners just for stiffness, and if it just looks cooler it's a win win.
You know pics are required?
Dan
A little overkill is normally how I like things I build lol.
I had thought about doing a lambeam but originally ejected it when I was thinking about spacing the boards around the knee braces, but I also worry about weathering if the ply. Although I plan to roof it there's still the possibility of rain exposure.
I didn't understand your comment about 12 or 14 not 8 or 10s...?
i wasn't planning on running beams on the sides, only the rafters because of the slope. So it would be knee braced on the front and back but not the sides.
this project is likely a couple months out. But here's a pic of the current deck area:
And here's the current layout sketch.
You are gonna walk into your knee braces on the low side. They are only 4' off the ground. (You didn't draw the low side- you faked yourself out by drawing only the high side).
Overall, it looks very good. I built a pergola last year with the exact same detailing- notched posts, spaced between, bolted connection. It worked excellent. Honestly, you probably don't need the knee braces on the front nd back if you do the joinery this way.
Consider adding knee braces at the ends, even if it's just the high side. You've got a potential wind load on the bottom of the roof, which could lay over the structure. If not knee braces, then a welded bracket connection between the girders and the posts.
How deep were you thinking of setting the posts?
The low side won't be a transit path. In fact the plan is to do a half wall with reclaimed windows above it that will be top hinged to swing out. Possibly the right hand side wall as well. The idea is to be able to open it up in the summer and close it up in the winter, at least on 2 sides.
so I don't have a girder on the sides bolted to the posts running up the slope. Just the rafters. Should I add one? And if so, what does the join between front/rear girder and side girder look like with the angle in play?
post depth... I was thinking 3' on the tall side, 30" on the short?
ultraclyde (Forum Supporter) said:
I didn't understand your comment about 12 or 14 not 8 or 10s...?
As loads increase, the beam has to be taller, 12" or 14" vs 8 or 10".
A lambeam for your application is overkill, but well sealed with a clear, it would look cool.
In reply to 914Driver :
Oh, right, gotcha.
im still leaning toward glued and screwed double 2x10s for the rafter support beams
I'm m also thinking about doubling the rafters over the posts and adding knee braces to reinforce front-rear loading after SVRex's comments.
