First time deck plans

I'm attaching my deck plans I submitted to the county. Really had two big concerns. First, deck's 25" off the ground (9.25" beam, 9.25" post, 1" decking) leaves me 5.5" for a post, so I'm thinking of going without a post and just have a 5.5" concrete pier connected to the beam. I'm just concerned about getting it all level and even. Maybe an adjustable post base? Second, I have a bay window and a gas fireplace bumpout that I cant attach to. I thought about doing a free standing deck but there's also a French drain in the way that would overhang way too much or leave me digging through fill dirt. Does this seem like a sturdy deck? Not bouncy or wobbly? Please take a look at the attached jpg and let me know what you think. Any suggestions or criticisms are welcome.

 

Triple 2x10 trimmers around the fireplace is overkill. (2) 2x10 is all you need. The double header is only supporting three or four joists with what appears to be a little over a 3' overhang/cantilever (up to 3' allowed for your joist span), so not much load there. And I would extend the "trimmers" (double joists) all the way out to the front of the deck (like regular joists). As far as the posts, why not go with 6x6 posts and notch them? Less concrete, easier to get plumb/level, and IMO will result in a stronger base. As far as rigidity, I would install diagonal bracing across the entire deck and also blocking where the joists intersect the beams.

What is the 8" round footing for?

Have you thought of ground cover under the deck? Landscape fabric with stone is one option.

 

Edited previous post and deleted this one to eliminate redundancy.

 

I dont understand your footings, typ you need posts down below frost line, you dont show your location?

 

Here is a copy of code for decks to cross check your figures. http://www.awc.org/pdf/codes-standar...Guide-1405.pdf

I'm glad I re-read it first as I initially read 25 feet off the ground. LOL At 25 inches off the ground, you should not have to worry about sway. I agree that 6x6's notched would be more DIY friendly set on your footers with base stand offs anchored in the cement. I don't think you have any other option other than to go free standing as there is no house to really attach to in your set up. Assume that your joists will be oriented north/south per your attached diagram and deck boards parallel to the house. Spend some extra time on the math so you don't have any sliver cuts on your deck boards. Speaking of deck boards, wood or composite? May have a bearing on the spacing of your joists if using composite. Blind or hidden fasteners do not in my opinion add much lateral strength as much as face nailing or screwing.

 

Thanks everybody for the replies. Point taken about the triple trimmers, looks like if you're under 8'6" (I'm at 5'8") you can just do double, and I'll run them across to the other beam, rather than run a separate joist. I do plan to do blocking between the joists at the beams. I'll definitely run some 2"x4"s diagonally on the bottom sides of the joists. Thanks for the tips. The 8" round footing is to account for too much over hang, since I can't attach to the bay window and I'm over 3'. I would just put a joist on that extra footing. Max overhang is 3'5" with 2x10 joists @ 16" OC and 3'1" @ 12". I plan on doing composite decking which calls for 16" joist spacing, but 12" for commercial. I would rather overbuild. I thought about detached, but with the French drain, I'd have to dig footings into the fill dirt next to the foundation. As far as the post, I was shying away from it because once it's notched I'd only have 5.5" post left which people have said would be prone to splitting with so much hardware going into it, just because it's so short.

 

I remember reading the same, but then I read somewhere else that the rule changed and it is now 1/4 the backspan of the joist, which in your case would be 3' (12/4). May want to check again to be sure.


If you notch the posts, the top of the post will be even with the top of the beam (14.75"). I was suggesting putting the posts in the ground and backfilling around, which would give you another 2' of length and a sturdier base (because the earth is supporting the post laterally, not just a bracket). Also, much less concrete to mix and pour, and you wouldn't need any forms. Dig your holes, fill with gravel base, pour footing, install anchor, secure post, backfill. Offset your carriage bolts to minimize the possibility of splitting.

 

Regardless if these are the maximum overhangs for the species of lumber, I believe you are still restricted by the 1/4 span rule. With your current design, that is 3'. Some counties (mine included) limit the overhang to 24". I would double check with the county building department to be sure. If it's 24", then you may been to rethink your beam placement.

Also, it looks like you can get away with one less post per beam. Space them 7' apart as opposed to 6' and you can have up to 1/4 overhang on the beams as well (almost 2'). Less digging and even less concrete