I’m an occasional visitor here, but mostly I’m a crossover from Knots. I’ve been comissioned (by my wife) to build a piece of furniture called a porch. It’s 14 feet wide by 12 feet deep. I’d like to have it supported at the outermost corners by notched 8X8’s rather than having an additional carrying member underneath. This will make it easier to walk under and make it look nicer (to my eye). Can you folks comment on the structural integrity of the design shown in the attached sketch? Is the doubled 2X12 sufficient to carry the load on the outer edge. Is there enough stability to prevent racking? Any advice is greatly appreciated.
Edited 3/22/2008 12:30 pm ET by Quickstep
Edited 3/22/2008 7:55 pm ET by Quickstep
Replies
I am a little confused...
The drawing shows notched 8x8 posts, and 2x10 joists, but you speak of notched 2x8 joists?
The drawing looks fine, except that I would add solid blocking midspan between joists, but the text description sounds undersized. It depends a bit on your location and snowload requirements.
Also, the drawing does not detail how often you would attache the ledger to the house with the bolts or what size the bolts are.
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he shows ipe in 5/4x6, does it come in these dimentions?
5/4 X 6 Ipe is pretty much what's available around here. It dresses out to about 1-1/8" by 5-1/2.
Yes
Actually it would easily span a framing layout of 24"OC if he is not in a snowload area. Shoot! the Ipe can stand more than that, but the framing would be getting questionable if expanded to 24" OC with 2x10But I don't know where the job is.
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It has been a while since I used IPE and then we could only get it in 1x4
I can't type. The text should have said 8X8's; I was referring to the posts. I've corrected it.
don't you think he should put a beam midway out from house? Might be bouncy otherwise. And I'd use doubled 2x for the rim joist, covering it with Azek anyway, why spend extra money on laminated beam.
no need for glulam but the doubled 2x12 fits my thinking 2x8 would span OK for 12' in the south with no midbeam, so the 2x10 makes it stiff enough to eliminate bounce
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Edited 3/22/2008 7:34 pm ET by Piffin
updated the tag line huh:)
it always reverts to text only when I do an edit. This site is set up to work with explorer and i use mozilla
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Good to see you here Paul. Did you get some mail from me?The best reward for a job well done is the opportunity to do another.
c-note gone postal;)
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Forgive me today, I'm exhausted. Would that be a yes?The best reward for a job well done is the opportunity to do another.
i use mozilla too, stops all the pop ups. Maybe I'll do a tag line, been here long enough.
I used Explorer to create the tag line for the WYSIWYG feature
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Use three piers, do not use the retaining wall for support.
Good catch on the retaining wall. I had been visualizing that as a log house wall for some reason, even though it is as clear as a bell on the drawing
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if he is worried about headroom, do you guys think that the 2x12's for beams are just a little overkill. I'm not sure about snow country but here in the south I would be o.k. with 2x10's to span 7 feet or so.
But, then again I would'nt need 2x10's for rafters to span that.
dug
EDIT- My bad after looking at the picture again I see that thats a floor system, heck I thought that was a roof for his porch. LOL, Carry on....
Edited 3/22/2008 6:41 pm ET by dug
First, if this is a porch, do you plan to have a roof as well? If so, you may need wider footing than the straight pier footing, and I would not tie that one corner to the retain wall since the retain wall can move. With a roof, even 12 inch pier may not pass as adequate footing.
I believe notching the post is ok to accept one thickness of 2x. Glulam is certainly not necessary unless you want more headroom under and you have to use treated glulam. Notching is not needed at all if you use post connectors.
For that height, I would either sacrifice the access with a cross brace or at least corner braces to connect the post to the beams. If you will have a roof, you may have to engineer the bracing system.
If you can step back the carrying beam, you can use 2x8 without the bounce. If you will have a roof, and want to keep it simple, you should have the beam right under where the roof rafters will rest to distribute the weight.
By the way, my town inspector allowed one story addition on piers with 8 feet spans and 18 inch footing under the frost depth, using double 2x10. This is part of my kitchen and have no problem, although digging was too easy and I put 4 feet spans, on average. I just wanted to over-do this part of the addition.
I would definitely get a permit for this and lean on the inspector for more structural information. My town engineer did allow me to make the drawing on my own on an I beam that needed more posts. This is one family house. That saved me some money on his inspection visit. But that was 2002 and since then the town became bureaucratic and stopped the HO involvement in that.
Hope this helps.
Looks OK, but I'd definately go with the 2X instead of the gluelam. And I'd lay the ipe on the diagonal to stiffen up the deck. Either that or add diagonal braces on the underside, but I prefer to lay the decking on the diag.
Mike Hennessy
Pittsburgh, PA
Thanks for the input from everyone. To answer some of the questions - yes, it should be designed for snow load since It's Maryland, though we haven't had any substantial snow in years. It will not get a roof, but for obvious reasons, it will get a railing, I was just too lazy to draw it.
I agree with others on not using the retaining wall as support unless it is footed below frost or on a frost-depth rubble trench.
The framing is adequate, but unless you're using 8x8s for the aesthetic, 4x4s are all that would be required and can be extended up past the notch (no more than 1½") to become your railing posts.
This makes a more integral structure and the railing will offer some rack bracing to the posts. Also, if you embed the posts a foot or so into the concrete piers, you can avoid the need for any rack bracing. Also, by embedding the posts, you can keep the concrete at or below grade and keep the look much cleaner.
With the structure as you've drawn it, it would need some bracing.
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Edited 3/24/2008 2:50 pm ET by Riversong
I don't want to start any arguement here on this ( we can save that for where it counts - ) but maybe you could clarify your thinking on the posts. If he notches a double joist into a 4x4 post, he only has a half inch left to extend up through for the posts of the railing.And I still would not use the retaining wall even if it is founded deeply. That horizontal wood can absorb moisture to shrink and swell with the seasons, moving that corner up and down.
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If he notches a double joist into a 4x4 post, he only has a half inch left to extend up through for the posts of the railing.
I said no more than 1½" on the notch, which means only the inner joist header. I do this with all my decks. It makes a much cleaner and sturdier deck and railing.
And I would agree on the retaining wall, but it looked like it might be planned to create an exit to ground from the deck.
Riversong HouseWright
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Edited 3/24/2008 6:56 pm ET by Riversong
I normally use a 6x6 for this sort of deck, not that it is necessary for the vertical load. Just looks right proportionally to sizes of houses.
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That is how I build my ext. Decks when I dont want the beam hanging down.
The last one, that I needed engineer on (Township Requested engineer sign off since it was not prescriptive), I have a triple 2x10 on a 15 foot span with center post so about 7 foot clear between 6x6 posts.
I believe 2@ 2x12 should work ok.
Tougher to build if you are by yourself but can be done.