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How To Square Floating Deck

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[OP]
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Jul 30, 2005
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How To Square Floating Deck

Going to be building my first wood base for a shed tomorrow and one problem I have a feeling I’m going to run into is the base not being perfectly square, which according to the instructions (and other people on RFD) for the lifetime shed is critical.

The Plan:
Base is going to be made out of 2x6s, 148”x93.5”. Going to be building it on deck blocks. Instead of laying the 2x6s directly on the deck blocks I’m going to be cutting up 4x4 posts and setting them vertical on the deck blocks, then attaching the 2x6s to the 4x4 posts with carriage bolts. This is to make the whole levelling process easier, I won’t have to try and level 9 deck blocks all to one another. I’ll use deck screws until all 4 sides are up and level and then install the carriage bolts. Next it will be the joists, 16” centres hung with hoist hangers. Lastly blocking in the zig zag down the center (still contemplating this, might be overkill).

The problem I’m going to run into I think is once I have everything nailed together and anchored to the 4x4s, if I measure corner to corner and they are not equal how do you correct that?

I read that on a “true” floating deck where it’s just sitting on flat cement stones, you can use ratchet straps on the long diagonal and literally pull it square, But mine will be attached to 4x4s sitting on cement blocks I don’t think it’s going to let me twist it?
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Jan 25, 2007
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Paris
Build the outside “box” which would be 4 pieces of joist material, measure it and make it square by nailing a 2x4 across the face after squaring, then add in your supports after. As you add each support, just do a square check.
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Dec 9, 2003
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When the diagonals are the same it is square. Tie a rope to the two long corners and twist.
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[OP]
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Jerico wrote: Build the outside “box” which would be 4 pieces of joist material, measure it and make it square by nailing a 2x4 across the face after squaring, then add in your supports after. As you add each support, just do a square check.
Interesting, so square a box off of the 4x4s first and then essentially lift it into place and secure it to the posts?
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Jan 25, 2007
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Paris
adblink182 wrote: Interesting, so square a box off of the 4x4s first and then essentially lift it into place and secure it to the posts?
I’d build it on the ground in place and then yes... just lift into place and attach to 1 4x4 and square from the one attachment point.
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Nov 17, 2012
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Using carriage bolts to fasten your joists to the posts is not ideal. All the load is on the bolts, not the lumber. The posts should be notched.

I know it's a PITA. I built a 9x12 bunkie on a PT 2x8 base which sits on simple footings with concrete blocks etc. to level it. I need to tidy them up a bit, jacking up a corner and replacing it with something nicer looking.

I started on one long side, from the highest footing and worked around keeping it level and mostly square. Then some nudging to get it square, a diagonal temp 2x4 brace and then plywood sheathing.

At that point I should have re-done the piers to make them nice looking before continuing, but I got in the framing zone and finished the basic framing in a weekend. It took another year to finish it completely but I managed to get it sheathed and ice/water shield on the roof before the fall.
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[OP]
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JWL wrote: Do you have a plan for cutting off the 4x4's after you have your rim joists level?
Hmmm I didn’t think it would be an issue so didn’t plan anything specific. Sawzall probably? Hand saw if needed?
[OP]
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torontotim wrote: Using carriage bolts to fasten your joists to the posts is not ideal. All the load is on the bolts, not the lumber. The posts should be notched.

I know it's a PITA. I built a 9x12 bunkie on a PT 2x8 base which sits on simple footings with concrete blocks etc. to level it. I need to tidy them up a bit, jacking up a corner and replacing it with something nicer looking.

I started on one long side, from the highest footing and worked around keeping it level and mostly square. Then some nudging to get it square, a diagonal temp 2x4 brace and then plywood sheathing.

At that point I should have re-done the piers to make them nice looking before continuing, but I got in the framing zone and finished the basic framing in a weekend. It took another year to finish it completely but I managed to get it sheathed and ice/water shield on the roof before the fall.
Very nice looking building. I hear what your saying on the notching the 4x4, but you have a lot more weight on those then I will. Mine is just a plastic shed, sure will have some lawn mower type of stuff in it but should be enough no?

So you did it differently? You built one side at a time and fastened it to the posts as you went? Not a box then lifted and attached to posts?
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Jan 25, 2007
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Paris
adblink182 wrote: Hmmm I didn’t think it would be an issue so didn’t plan anything specific. Sawzall probably? Hand saw if needed?
I did the way easier approach. Measured what i thought I needed and then cut on the mitre saw. So long as you have at least 2/3rds of it beside the joist, and obviously not above the top you are golden. You should have at least an inch to work with of up/down to make it right.
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Oct 14, 2010
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Having done this once, working alone, I learned a few things from my mistakes. Your deck (12x~8) is a little bigger than the 8x4 I did, but this procedure should let you build it single handed.

I would assemble the outer 4 sides of the box together. Next I would screw down a 1/2 sheet of plywood (4x4) to one of the corners which will assure you that the box is square, and will stay that way when you move it. I prefer this over the measuring and cross bracing, because there is no chance for an error during measurements. At this point the assembly is still light enough that you can drag it into the location you wish to build at.

Place the box in the location you want to build in. Mark the four corners on the ground, and then pull the box away again. Prepare the ground at these four points to accept the deck blocks. Ideally level the ground and place a 24" patio stone, centered in the area where the deck block will be. I like to use a laser level at this point to make sure all the patio stones are at the same level. Trying to level this later when the weight of the wood is added is extremely awkward and difficult.

You will be placing the box directly on these deck blocks (without 4x4's) so make sure these corners are a few inches higher than any of the ground in the middle, so that you have the space to add a deck block and a short 4x4 post in these middle locations. Optionally if you want to make the deck as low as possible, you can dig out the high areas in the middle and "sink" the deck block to make the required space.

Now place the box back in the final location over the patio stones. Lift each corner in turn, and slide a deck block under the corner. I would not use 4x4's at these corners because the notches on the deck block will help to keep everything square and level. Note that you would never be able to put all four deck blocks in the perfect location beforehand and then place the box on top of them, so slide them in, one at a time.

Now that the frame of the box is square and level, start adding the joists. I won't make any suggestions as to which direction to place the joists, or how many additional supports (4x4's) that you will need, but I suggest you add the supports immediately as the joist is installed, and not wait until after all the joists are installed. This gives you the benefit of having room to stand or squat on the ground and prepare the ground for the deck block, rather than trying to level soil and move deck blocks while laying on your belly and reaching between the joists.

Of course you will need to remove the plywood as you get closer to that side, but the box will remain square at this point.
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adblink182 wrote: Very nice looking building. I hear what your saying on the notching the 4x4, but you have a lot more weight on those then I will. Mine is just a plastic shed, sure will have some lawn mower type of stuff in it but should be enough no?

So you did it differently? You built one side at a time and fastened it to the posts as you went? Not a box then lifted and attached to posts?
Mine isn't on posts at all - the rim joists (doubled up) sit directly on the concrete blocks/wood etc. No posts, just built up piers. I'm just saying you don't want the weight of everything in your shed supported by a few carriage bolts if you can avoid it.
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Thanks for all the tips. I've working on it for 2 afternoons so far, it's been going fairly well.

I made the outside box on the ground first, squared it up and then temporarily screwed diagonal supports to all four corners. That held it square for all of the blocks to be dug, 4x4s cut and fastened, and joists installed. I was surprised how well it went, everything ended up very level despite the box being built on uneven ground.

We used scrap wood as leveling blocks to see how high the box was going to be from the deck blocks so we could cut the 4x4s to length as Jerico mentioned.

I went with 8 blocks total instead of 9, went both 2 in the middle instead of 3.
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