My new deck is out of square

[FS7]

Sigh. I just build a 12'x40' deck, mostly ground-level (from ground level to about 16" above, actually, corner to corner). I did this because I like wood and both pavers and concrete were much more expensive and more work. I had a ground-level deck at my old place that lasted 20+ years (still going strong) despite having little airflow so I have no concerns in that regard. Many people tried to talk me out of it.

The home's foundation isn't a smooth surface (stamped brick-type concrete) so it wasn't the most ideal reference point. I used plumb bobs from my existing second-story deck (12'x20') to mark reference points, put in stakes, and then used those along with the house as a reference point to extend the other 20 feet. I checked for square along the way, but what I ended up with is a parallelogram with 89 and 91 degree angles. Corner to corner the difference is about 5 inches, which is pretty minor, but the 1 degree difference works out to about 4 inches over the 12 feet of decking. Since it's a flush beam design and I couldn't put footers right next to the house, I decided to have the boards perpendicular to the house with the joists parallel. Now I have to cut a one degree miter in the end of every board. 

It's not like it will ever be noticeable, but it is a pain. Why oh why did I ever assume that existing things were square? It's my own fault, I know, and in retrospect I could've planned for closer joist spacing to allow for 45 degree deck boards to hide the problem.

[CLETUS]

 Why oh why did I ever assume that existing things were square? 

I don't know... that is one of the fundamentals of building anything.

[JGrout]

Pulling a diagonal on the frame would have shown your error at the post stage when it would have been easier to fix 

And frankly at this point it may be worth the effort to figure it out than to proceed..

JMO

[FS7]

I don't know... that is one of the fundamentals of building anything.

Not around here it isn't.

Pulling a diagonal on the frame would have shown your error at the post stage when it would have been easier to fix 

And frankly at this point it may be worth the effort to figure it out than to proceed..

JMO

I checked at the corners but not the diagonal, which would have been better, especially since I was apparently rushing on the corners. Nonetheless, I don't feel there's any real point in doing anything now other than mitering the board ends for a neat appearance. The opposite sides are parallel and the deck is level, so I am not concerned about anything structural. I know how it happened - my point of reference was not square, but the existing second-story deck boards are parallel to the house, which hides the problem. The deck is not racked - it is simply out of square.

[Phil Thien]

Aren't you better off maintaining the same error as on the other deck?  Had you made the new one square, I'd think the other deck would have looked wonky?

[FS7]

Aren't you better off maintaining the same error as on the other deck?  Had you made the new one square, I'd think the other deck would have looked wonky?

You're probably right, even though the other deck is nine feet higher. I have to imagine standing on the edge at the bottom where two sides of both decks are parallel it would be obvious that they aren't aligned. I hadn't thought of that.

Then again, standing on the other corner makes it somewhat apparent that the side of the deck is slightly off with respect to the house, but that's probably a lot less obvious due to the uneven brick/concrete formations as well as the naturally sloping grade going up that side of the house.

This actually makes me feel a lot better, because there isn't a great solution to this beyond what I did.

It just amazes me how often things are square, but it amazes me even more that I was surprised by it. In my old house, I was acutely (haha, I'm such a comedian) aware that absolutely nothing was square or level in that house. Hell, in the process of doing this, I realized that the door threshold on the basement is not level, though the deck joists and trim underneath it are perfectly level. It's just kind of odd for me as I'm working on two projects - a crib for my daughter, which I'm trying to make as perfect as possible, and the deck, which is as "construction" as it gets, so the shifting gears sometimes don't catch up.

[Foggy]

Any thoughts on putting the deck boards in an angle. Seeing as you have to trim the ends anyway it would not be much more work. I did an eight foot deck that looked neat that way. Stronger too. I chose the angle by using ten foot boards and just trimming the ends. You can hide a lot of irregularities this way. I estimated that there was about two boards lost in trimming the shorter pieces for the corners.

[FS7]

Any thoughts on putting the deck boards in an angle. Seeing as you have to trim the ends anyway it would not be much more work. I did an eight foot deck that looked neat that way. Stronger too. I chose the angle by using ten foot boards and just trimming the ends. You can hide a lot of irregularities this way. I estimated that there was about two boards lost in trimming the shorter pieces for the corners.

The deck is 12' wide, so I would need 17' boards (at 45 degrees) without adding additional blocking to support butt joints. It's a lot harder to find 20' lumber, and it would increase waste quite a bit in my case. Also, I would have designed the joists a bit differently if I were going to do 45 degree boards. I know it looks nice (very nice) and it is one of the best ways to hide irregularities and if I could do it over, I might very well go that route and just have a huge pile of 20' boards delivered rather than picking up the 12' boards myself.

That said, I could use 16' boards at a slightly lower angle (say 30 degrees). I wonder how that would look - I may check it out when I get home.

[DaveHo]

Maybe I'm missing something, but this doesn't seem like a big deal.  Where the boards meet the house, butt them as tight as you can.  Nobody will notice the small gap being 1 degree off at one edge of the board.  At the outside, run the boards long, snap a line & cut off with a circ-saw such that the board ends follow the framing.

[Roly]

Remember if you install the decking at a angle you are also increasing the span distance for the decking. 16" centers become 22.6" centers if at 45 degrees. Roly