Carpentry people: Deck questions

[Gunslinger08]

I'm having a deck built. It's going to be 24'x14' and free standing. The contractor is a respected deck builder in my area who has been doing it for 20+ years. I trust him, but I just want to be sure that I'm having him build a stable deck.

He has dug 8 post holes, 4 against the house and 4 at 12' out, leaving a 2' cantilever. I live in Virginia (snow) and I'm using composite decking (heavier but more flexible). The deck is approximately 9' off of the ground. What sizes of posts, beams, and joists should I be looking for? What spacing on the joists? How much will bracing add to the stability? I don't want the deck to feel spongy or unstable when I have family and friends over.

 

[VulgarDisplay]

I'm confused? Is the deck attached to the home? If so why are there posts next to the foundation? If anything it sounds like he's overbuilding so i wouldn't worry.

For a 12 foot span I would want 2x12's to try and eliminate some of the bounce that may be in the deck. It's kind of a no brainer, but look for pressure treated lumber, and keep an eye out for a few things. Look for 45 degree angle lumber underneath going from your posts up to your outside beam to eliminate sway, and make sure that your railings have a continuous plate that goes over the top of them. It makes them stronger than just sections between the posts, and gives you a great place to set down your beer. Also, make sure the ledger board is attached to the house with lag bolts, and has flashing over the top of it to make sure that ice isn't able to heave it off the house.

As for the beam, I am not a fan of setting the beam on top of the posts and then joists on top. When I was framing for a living we always put our 2x12 beams on opposite sides of the posts and then bolted through the whole thing.

Finally, check what type of fasteners are being used. Treated lumber is extremely corrosive to plain metal fasteners. Read here for more information:
http://woodworking.about.com/od/safetyfirst/p/SafeACQLumber.htm

 

[Anubis]

did something similar this summer, Vert Posts are 6x6s that are notched with either 2 2x8s or 2x12s on them and 2x8 for the decking supports sitting on those

 

[Gunslinger08]

I'm confused? Is the deck attached to the home? If so why are there posts next to the foundation? If anything it sounds like he's overbuilding so i wouldn't worry.

I have a finished basement, so he couldn't tell whether or not I have a solid endplate at the end of my floor joists. I suspect that I do not, as all of my floor joists are engineered. I also just feel better with actual supports at the house vs. just a ledger board. He still puts a ledger on to provide lateral support, but its not structural/load bearing.

I'm mostly just concerned with the 12' joist span and what spacing I would want for good stability. I'm not even sure what size posts he is using. I think that 4x4 would meet code, but I think I'd feel better with 6x6.

 

[skyking]

The size of the post is not as important as the shear bracing. Make sure it has plenty of that.

 

[SearchMaster]

4x4 will be fine unless you're planning a hottub.

 

[grohl]

sounds like you are pretty handy, or at least knowledgeable enough. why didnt you do it yourself?

 

[Gunslinger08]

sounds like you are pretty handy, or at least knowledgeable enough. why didnt you do it yourself?

Lazy and I just wanted it done without having to think very hard. It's definitely nice to just pay money and see progress when I get home each day. I finished my basement and built my own fence. I'm just tired of all the ancillary crap, like shopping for and transporting materials, borrowing tools from my dad, researching code requirements, cleaning up, etc.

 

[Greenman]

2x8 joists will be fine, assuming pressure treated doug fir joists.

 

[Humpy]

What standards does the contract indicate the deck will be built to? How do you know what you are paying for?

A 2x8 joist is NOT acceptable for the span with an overhang as described. A 4x4 post is NOT acceptable for the deck as described.

If for some reason anyone hires a deck builder that they don't trust and need reassurance then read this: http://www.awc.org/publications/DCA/DCA6/DCA6-09.pdf

Any contractor should already be familiar with the information in the document. That is the basic stuff they are paid to know. If they don't, you have a problem.

 

[VulgarDisplay]

2x8 joists will be fine, assuming pressure treated doug fir joists.

He wants a deck not a trampoline.

 

[MagnusTheBrewer]

This needs more MS Paint or, diagram, sketch, whatever, with some dimensions. We can't answer how high is up questions without details.

 

[edro]

1. 6x6 posts are now being required by many building codes. 4x4s have been used for a long time though.

2. According to the book I bought when I built my deck, a 2x8 joist made of Ponderosa Pine (Southern Pine is stronger) can span 12'1" when spaced 12" on center. (southern pine can go 14'2")

3. Composite decking usually requires 12" joist spacing because they are much more flexible than wood planks. Make sure you see what the manufacturer recommends. If he uses wider joist spacing, it will definitely result in a bouncy deck. 16" spacing is standard for wood.

4. Make sure he puts in some 2x8 blocking between the joists. Halfway across the joist span, put blocks between the joists. This helps tie them together and stiffens everything. The deck boards do this as well, but the 2x8 blocks will be better and is recommended by every resource I have seen. (books, websites, etc)
http://www.decks.com/deckbuilding/Deck_Blocking_And_Bridging

 

[jupiter57]

I built this on my house this spring:

It is 14' x 20', on 4x4's, using 2x8's @ 16" O.C. for joists.
4 - 4x4 posts on each side, 3 on the South end, 4 on the North end (For handrail). Centered one in the middle of the deck with 2- 2x8x 14 on either side & used Joist Hangers.
Ran my joists parallel with the house, splitting them at center to utilize 10' joists (much stronger), and used 14'- 5/4" decking run perpendicular.

It is only 4' at its highest, but if I were going with a 9' height, I would surely use 6x6's!

 

[Greenman]

He wants a deck not a trampoline.

It's in interesting thought, but 2x8 DFPT joists @ 16" O.C. are compliant. Deflection should average 4/10" with 40 pounds per foot live load.

 

[Humpy]

I built this on my house this spring:

Nice. Running the decking as you did is more traditional (think boardwalks and covered porches) and much better looking IMO. Plus, some argue that overall function is improved as run off is potentially channeled away from the structure.

 

[MagnusTheBrewer]

It's in interesting thought, but 2x8 DFPT joists @ 16" O.C. are compliant. Deflection should average 4/10" with 40 pounds per foot live load.

Yet another reason why being "up to code" isn't good enough.

 

[edro]

Perhaps a more important questions is: How wide and deep are his footers for the posts?

 

[Greenman]

What standards does the contract indicate the deck will be built to? How do you know what you are paying for?

A 2x8 joist is NOT acceptable for the span with an overhang as described. A 4x4 post is NOT acceptable for the deck as described.

If for some reason anyone hires a deck builder that they don't trust and need reassurance then read this: http://www.awc.org/publications/DCA/DCA6/DCA6-09.pdf

Any contractor should already be familiar with the information in the document. That is the basic stuff they are paid to know. If they don't, you have a problem.

That's a very informative document. The span tables are about 10% shorter than what my reference material has listed.

 

[edro]

Post and joist sizes are so easily upsized and the cost is almost nothing.
I don't see why anyone would want to skimp in that area.

If the contractor hasn't started the joists yet, tell him that you want 2x10s with 12" spacing. The material and labor increase will be relatively small.

 

[Greenman]

Yet another reason why being "up to code" isn't good enough.

Actually, it is good enough. I've been in the industry for 35 years, and I've never seen a code compliant deck fail do to meeting code. I've never even heard of it happening.

 

[Humpy]

That's a very informative document. The span tables are about 10% shorter than what my reference material has listed.

They are a little more conservative than the floor joist charts in the IRC. In my area it has become the de-facto code for building decks. Anyone who pushes the fact that it is not the official, legal code gets a quick lesson in building inspector relations management.

The link is a pretty good guide for anyone building a deck, whether a permit is required or not. With variance in lumber quality from tree farms and the potential for sudden collapse that is somewhat unique to decks, it is not a bad idea to overbuild.

By the way, for anyone who is interested, most current building codes are freely available for download from https://bulk.resource.org/codes.gov/ and/or http://archive.org/details/publicsafetycode. If someone wants to DIY under the radar while still "meeting code" it is nice to have access to the rules without having to shell out a couple hundred bucks to buy the books.

 

[Humpy]

Actually, it is good enough. I've been in the industry for 35 years, and I've never seen a code compliant deck fail do to meeting code. I've never even heard of it happening.

The critical area of the ledger connection to the structure is under addressed in code IMO. Specifically with flashing, it seems to leave the execution up to individual interpretation. Nearly all code compliant deck failures that I am aware of are due to water intrusion and rot at the ledger board.

Free standing decks, like the OP is having built, are ideal because they avoid the issue almost entirely.

 

[Greenman]

Here in the land of fruits and nuts, we have a plethora of standards to meet. I have plans sitting on my desk right now that site ten different codes/standards that have to be met. It's getting out of control.

 

[VulgarDisplay]

The critical area of the ledger connection to the structure is under addressed in code IMO. Specifically with flashing, it seems to leave the execution up to individual interpretation. Nearly all code compliant deck failures that I am aware of are due to water intrusion and rot at the ledger board.

Free standing decks, like the OP is having built, are ideal because they avoid the issue almost entirely.

I think the OP is in good shape with his contractor because he was smart enough to realize that the box sill was most likely plywood and opted to not rely on it to support the ledger board. I'd stop sweating it because your contractor seems to know his craft.