My new deck is out of square

[packerguy®]

The first few times I built things I just assumed things were plumb, level and square if it looked right. 

I learned my lesson, and now can hardly hang a picture without a level. 

[FS7]

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.

You're correct, it really isn't. I'm just a little bit too much of a perfectionist to let it slide. Of course, I tend to over-engineer and over-design everything, so I installed all the trim (the frame) at deck height so I could install the lights. After all, I needed to wire it up before I put the boards on. This slightly complicates trimming with the frame as I have to raise it slightly. Nonetheless, it seems to be working out OK. Of course, if I were a normal person who didn't do lights, I would be able to lay them all flat and trim them that way. I should note that 24 boards in, the angle (thanks to the inherent variance in deck boards) is more or less 90, so I can just butt them now anyway. Then again, I know the angle is the same on the other side, so that's no fun.

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

This is why I didn't go 12" on center. Once I had committed to perpendicular boards (and wood), this let me go to 16" on center for the joists. I would have done 12" for 45 degree boards or composite.

[jamesglenn]

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.

A few years back I had a similar issue when I modified the layout of and installed new decking on my existing deck. I checked the framing for square and everything and found it to be a mess. It also had a octagon gazebo at one corner which was not close to equal sides.

I didn't want to spend the money for the 20ft deck boards either, plus I had already bought the 12ft composite boards, so I created a accent color square in the center where the longest boards would be needed. I figured the location where I could get a full 12ft deck board when laid at a 45d angle, and then set up the accent square by establishing the other side in the same manner. Also, when at an angle you can maximize the coverage of the decking by paying attention to how you cut the longer pieces and use the shorter leftover for the smaller boards at the corners.

It looks great and I have only had one designer and/or contractor friend figure out why I did it.

[geek2me]

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.

What is "square"?  What is the tolerance on the measurement?  Nothing can ever be truly "square", and there is a tolerance on the measurement.  A one degree error on a 90 degree error is well within tolerance for essentially any construction standard.

Are you not using a shoe molding over the end at the house, and trimming the free ends of the decking after completion?  Not sure why you would need to cut a one degree miter.

[George Denecke]

I thought it was against the building code to be perfectly square.

[Foggy]

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.

For 12' wide use 14' boards and trim just the corner off each end. The angle will be whatever it is. Or have the boards butt together to form a V at the center of the deck. If you don't think 'square' the possibilities are endless.

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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.

See how you like the angle using 14' boards. Or possibly butt the boards  together to form a V in the center of the deck. 
once you go beyond thinking 'square' the possibilities are endless.

[FS7]

For 12' wide use 14' boards and trim just the corner off each end. The angle will be whatever it is. Or have the boards butt together to form a V at the center of the deck. If you don't think 'square' the possibilities are endless.

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See how you like the angle using 14' boards. Or possibly butt the boards  together to form a V in the center of the deck. 
once you go beyond thinking 'square' the possibilities are endless.

When I designed everything I did all the joist span calculations and planned on doing 12 footers, with five 8' x 12' sections. The total area is around 12'3" x 39'6" or so (with trim) so there are four equal 8' sections and one middle section that's slightly shorter. I did 16" joists since that was more than adequate for 5/4 SYP decking, which is what I used, even if I decided to go 45 degrees. To save on materials, I decided to do perpendicular boards, but the orientation is such that any imperfections show up.

What I ended up doing was cutting one degree miters in the boards to have them all butt up neatly at the house edge for the outer four sections. The middle section is done at 45 degrees, which will hide the fact that it's not a square (otherwise there would be a wedge or oddly tapered piece). It looks pretty good and I doubt people will notice. It ends up working as an accent (the upper deck is 12' x 20'), since it serves as a transition between the exposed part and the shaded part (exactly half of the angled section is under the existing deck).

I think if I could do it all over again I'd probably do it all at an angle. But, live and learn. Someday it'll need replacing, and then I can do whatever I want.