How do I repair posts bowing on 104 square foot deck?

Question

I have a 104 square-foot second-story deck that I built with a friend last year. It's supported by four 4x4x16 posts on solid concrete pilings that go 6 feet into the ground. The deck is stable, but I have noticed that in the last year the 4x4 posts (pressure treated pine) have twisted and cracked a bit -- due to wooed being cut when it was wet, a common problem -- and two of the outer posts have bowed about 1 inch away to either side of the deck. Do I need to replace these posts, and if so -- how do I do that without taking down the entire deck? Should I consider replacing them with 6x6 posts, perhaps out of another wood like Cedar?

Answer 1

Bowing, twisting, checking, these are all common traits of treated lumber....
Most treated lumber does not get the same amount (if any) of kiln drying that non-treated gets. (usually 6to 8% moisture content). It would be a bit of a waste of time to draw the moisture out of the treated lumber.... only to steam cook the stuff to put the copper nitrate, or other chemicals into it. The 'treated lumber' is literally sopping wet, after it has been commercially treated. So, no matter what size treated posts you use, it will likely twist, bow, or check/split.
Most treated lumber also comes with a warranty on it... its usually that little tag on the end of the board.... hopefully you saved those. You may have a possibility of getting them replaced, if they are deemed defective.

Myself, I always tend to overbuild... If I can use a 5x5, or 6x6 where most folks would put a 4x4, I will. That doesnt necessarily mean your posts must be replaced. You don't say if the bow is at the top of the posts, or down farther towards the middle. If it is just bowing out in the middle, then you can 'pull' them back in place, using either a hydraulic puller, or a 'come-along', and attach a cross brace, to hold it in place. Actually, you could do something similar if it is at the top too...

Should you decide to replace the posts.... you can support the deck with temporary posts, while you remove the old ones. A hydraulic jack would be handy too...to raise the deck an inch or so, to make installation easier. If you take two temporary posts per corner, you could span the underside of the deck, across the corners, thus supporting all sides of the deck. I would also, for safety reasons, tie these temporary posts together, by crossbracing.

Your best bet, to prevent twisting supports in the future, is to 'laminate' some timber together. For example, glue and screw 3 - 2"x6"x16ft together, making one post out of them. This would be an extremely stable post, and would resist twisting, etc. I would also use an untreated lumber... fir, would be good, and either stain and treat it, or paint it, myself. (you can even get that copper treatment, if you want)

6ft pilings -- my commendations! Ive seen too many people skimp on the foundations to their later frustrations, heheheh

Remember - Safety First! Whatever you decide to do... do it carefully, and with thought.

Answer 2

My God there are some word-y answers here! You had it right all along. Divide your square foot area by .5 or multiplying by 2 is the same answer. 3600 linear feet is a little too much I think. 3300 should cover it.This is for your estimate only. Most of the other information is more applicable to your builder than yourself, but I think an eighth inch is a little light on the spacing, but no more than a quarter - I've never seen the spaces on a deck get smaller, but starting too small will just cause the deck to fill up with organic crap. The boards will shrink in the elements more than expand. If you use synthetic, they won't shrink, so the gap should be large enough to wash dirt through easily.

Answer 3

I would replace the post, you can use a jack or blocks to hold up the deck while you replace those two. I would stay with the treated ones,and maybe that is an area that has more weight on it. Maybe think about using a 6x6 or two 4x4's put together on each side. I hope this helps.

Answer 4

It depends on the amount of weight the posts are supporting. If you there is any sway in the structure, then you may want to think about replacing the posts. If you don't care about how they look, you can also shore up the structural integrity of the posts by bolting additional posts to the existing ones. This will also keep the old posts from bowing any further.