Kids playdeck...help!

[pslamp32]

So I thought I'd build my son a little playdeck / swing / slide. I built the deck about 4.5' off the ground and the deck is about 8'X8'. I used 4 posts which are 4X4s and the deck 'framing' (not sure if this is the proper wording) is made from 2X6s. I added 3 - 2X6 joists and the framing is covered with 5/4 X6 decking. Everything looks great and feels solid when I walk on it but then I got paranoid that I should have used 6X6 for posts or maybe added at least 2 more 4X4 posts for support. It's too late to add the extra posts. I've never built anything like this before but it seemed pretty simple although I didn't really think too hard about it obviously. Am I getting paranoid for nothing? Thanks!

Here's a picture from my crappy camera phone to give you an idea what I'm talking about. This is before I added the decking obviously.

I still need to add railings, a slide, a ladder and swingset off the side of the deck. All that weight makes me a little nervous.

 

[TXnNC]

Peter,

Wife and I built this one out of 4x4s last fall and so far no problems. As long as you anchor (quikrete) the legs well, it shouldn't be a problem. Yes, it will swing some if the kids start playing hard, but never anything to cause concern.



Ken

 

[LeftyTom]

Should be plenty sturdy.

 

[TracyP]

4X4'S Shouldn't let it go anywhere, looks like a fun place to play!!

 

[cptully]

Peter,

Being a Materials Engineer by training, I've been working through Bruce Hoadley's Understanding Wood text - essentially one of my college texts rewritten for wood instead of metal! :gar-Bi

That and a quick Google of "lumber span chart" give me the confidence to say you are fine with the design you've chosen. The allowable span for 2x6's 24 in OC in house floor is approximately 8 feet. You can get longer spans on decks because there is typically less loading (live and dead). Based on the pick you sent, you've used about 24 in spacing. I would probably add four more joists to stiffen the floor (span at 12 in OC goes up to 10 + feet for 2x6).

As for the 4x4 versus 6x6 question keep in mind that wood is a lot stronger in compression than tension. Roughly quoting Bruce Hoadley, this means that a 1/4 in dowel is enough to support the weight of a typical sitting person, if it were used as the leg of a Windsor chair; however it cannot resist the side loads, which is why we make chair legs larger than 1/4 in dowels! As long as the 4x4's are securely anchored in the ground for at least 1/3 of their length, you should be fine. Since this is a play structure, I would bury the concrete about 2-3 in below ground (to protect the kids), and slope the top of it away from the post (to protect the post). Also, put about 4 in of 3/4 gravel in the bottom of each post hole before placing the posts and pouring concrete, to allow the post to drain.

Chris

 

[McRabbet]

Peter,

Chris has hit on several things of importance; I've built several decks that conform to the NC Code (Appendix M of 2002 NC Building Code; also see 2006 Amendments Residential Code Appendix M) -- 4 x 4 posts are fine if properly embedded and spaced. NC Code requires 42" deep embedding in 12" diameter holes for decks; 2 x 6 joists on 16" centers can span 8'. If posts are more than 8' from ground to structure, they must have diagonal braces.

Here are pictures of a 9' x 12' deck I built in 2006
The braced posts support a 2 x 6 beam that hold 9' joists. Only the front corner post required braces, but I braced all for balanced appearance. All bolts are 5/8" galvanized by code. Platform beyond deck is for stair landing shown below.


Finished deck and stairs.

 

[pslamp32]

Thanks all! I feel a little better now. Maybe I'll add a few more joists. Rob, are you sure it's 42" deep? When I had my main deck built in the spring, the code office told me 18".

 

[dave "dhi"]

deck footings need to be 12 inches deep, 16 inch square with at least 8-10 inches of crete(1 1/2 bags of 80 pound cret). i dig plenty of them in a years time!!:BangHead: dave

 

[McRabbet]

Rob, are you sure it's 42" deep? When I had my main deck built in the spring, the code office told me 18". (pslamp32)

deck footings need to be 12 inches deep, 16 inch square with at least 8-10 inches of crete(1 1/2 bags of 80 pound cret). i dig plenty of them in a years time!!:BangHead: dave

It all depends on your local inspector and the size of the deck. Dave's 16" square footer will support a post for 70 sq ft of deck area. I had proposed 24" deep in 12'' holes on the deck I showed and they replied that I needed to have them at 3'-6'' deep. Yes, I agree that is is overkill because my deck was not freestanding -- at least they didn't require 6 x 6 posts (see paragraph 8.C. in Appendix M)!

 

[Steve W]

McRabbet, your building inspector in town must be a transplanted Yankee :rotflm: Being one myself, I've seen 12" to 18" depths quoted around here -- never 42" since I left Massachusetts. The reasoning is to get the footing below the frostline. Possibly because Hendersonville is in the mountains and it gets colder there?

Man, 42" is a lot of heavy clay to excavate!:elvis:

 

[pslamp32]

No, I live in Asheville right next to Rob. My inspector said 18" deep and 18" square. My deck was 18' X 12'. Weird.

 

[McRabbet]

McRabbet, your building inspector in town must be a transplanted Yankee :rotflm: Being one myself, I've seen 12" to 18" depths quoted around here -- never 42" since I left Massachusetts. The reasoning is to get the footing below the frostline. Possibly because Hendersonville is in the mountains and it gets colder there?

Man, 42" is a lot of heavy clay to excavate!:elvis:

I tried to get him to change, but he wouldn't budge -- it took two of us an hour to dig the seven holes with a 2-man auger and then it took me six hours to shovel out all of the dirt into my truck! We don't have frost here like NY where I'm from or New England where you're from, but the deck won't be falling down anytime soon!