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-   -   Fixing out of square deck posts (http://www.diychatroom.com/f19/fixing-out-square-deck-posts-70026/)

Starbuck II 04-28-2010 01:45 AM

Fixing out of square deck posts
 
Well I have discovered a problem with a deck I am building.
When I poured the 12" x 24" deep footings, I used the 3,4,5 rule, everything looked good. I dug the holes, put in concrete tubes, filled them with concrete installed the post anchors while the concrete was wet, checked 3,4,5 again, it all looked good. Left town for a couple weeks, it rained I heard while I was gone. I drilled the posts to match the anchors, mounted them up & began to build the sub floor. It was 3/4 of the way thru that I found that either the concrete shifted in the ground during the rains or the anchors moved slightly while curing.

Long & short of it is that on a 10'x12' deck, it is out of square on two spans by about 3" over 10-12'.

I am really frustrated because I was so careful to measure everything several times.

the deck is rectangular with a corner clipped so I have 5 posts & it appears that 2 of the posts nearest the block wall might have moved.

Is there anyway to square this up without starting over?
What is the likelihood of being able to dig around the footings & move or pry par the 200lbs plus footings the needed 3"? Or is that simply crazy?

Will I create more problems than I solve by now maybe loosing level as well? right now everything is very level.

Please advise.

Scuba_Dave 04-28-2010 08:32 AM

Where are you located ?
Pics of the issue ?
How far off the ground is the deck ?

Starbuck II 04-28-2010 09:37 AM

I don't have pics, the deck is only going to be about 8" off the ground, but there is a roof that will be over it using 4x10's & so that can't be forced to align.

Think of a rectangle with a corner clipped off.

Sides would be 12', 10', 8', 8' & 40"

the 12' side is 3" out of square by the end of the run.
the 8' side that connects to that 12' side is also 3" out of square.

any ideas how to straighten it?

tpolk 04-28-2010 09:46 AM

is that 3" on the diagonal? so only 1.5 to square it?

Yoyizit 04-28-2010 10:48 AM

Quote:

Originally Posted by Starbuck II (Post 434611)
dig around the footings & move or pry par the 200lbs plus footings the needed 3"?

And then pour more concrete in the enlarged hole. This might be the best option.

12penny 04-28-2010 11:18 AM

starbuck... I think I'd move the post bases/anchors. Not sure which ones you're using. If they're simpson bases just cut off your anchor bolt, drill another hole and install some kind of wedge anchor to hold the base down. Sure beats digging them out.

Starbuck II 04-28-2010 11:35 AM

The 3" is on the perpendicular.

The anchors aren't bolts. They are the kind where there is significant steel in the concrete. cutting them off would not work because there is steel embedded in the concrete where I would have to drill.

I wished that would work.

I have thought that maybe adding a short daughter post in the mount then attaching the real post to it with bolts. I am afraid that however wouldn't give me the load bearing value I need.

I wished I knew a better way than digging. Anyone got any other ideas?

Willie T 04-28-2010 12:19 PM

Quote:

Originally Posted by SB II
I used the 3,4,5 rule, everything looked good. I dug the holes, put in concrete tubes, filled them with concrete installed the post anchors while the concrete was wet, checked 3,4,5 again, it all looked good.

Contrary to popular belief, the method described is really not all that accurate, if not also checked by pulling diagonal measurements.

Seriously, the 3,4,5 rule (or the 6,8,10 rule) is good only for roughly getting you in the ballpark of a 90 degree corner.

Each time you turn a corner and reapply your 3,4,5 rule, you introduce an additional chance for error. And if the actual numbers used are not almost as long as the deck run, itself, there is still more chance for error.

Always use the Pythagorean Theorem to determine your true diagonal measurements. And double check just before cutting any boards.

It honestly is not all that likely that some rain, alone, caused this much of an error. And I say this because you wrote that you didn't check again when you returned home, but rather drilled to the holes where they lay... and the fact that everything is still 'very level', reinforces the premise that nothing moved. If the columns shifted, they would have done so by tilting and/or sinking, not by smoothly moving in a parallel and vertically plumb attitude.

I know this doesn't help you much with this current dilemma......... but I'm writing this for the next guy here who decides to just pull a 3,4,5.

Also.................. You will NOT be able to move the columns and retain level accuracy by digging down along side them, then trying to pry them sideways. The tops will move, but the bottoms will resist.... and they will scuff themselves deeper into the ground as you attempt to move them. This is not a big deal, as you can always make the posts for those columns longer... but keeping them plumb is going to be a monumental task.

Starbuck II 04-28-2010 02:05 PM

So is there any solution at all? is there anyway to fix this short of blowing it up & starting over?

Yoyizit 04-28-2010 03:13 PM

Quote:

Originally Posted by Willie T (Post 434763)
Seriously, the 3,4,5 rule (or the 6,8,10 rule) is good only for roughly getting you in the ballpark of a 90 degree corner.

No.
The arctan of 4/3 is 53.1 and the arctan of 3/4 is 36.9.
This totals to 90.0.
The remaining angle must then be 90.0.

3" out of 12' is a 1.2 error. This error magnitude may reflect ordinary effort, given the conditions you worked under. With extraordinary effort you might significantly reduce this error.

5:12:13 also works, and this seems more suited to your dims. Using aluminum angle to make this huge square will assure straight sides and high accuracy. And you can fold up the whole thing.

Surveyors, of course, would want much better, over a distance of 12'.
http://www.google.com/search?client=...UTF-8&oe=UTF-8

Willie T 04-28-2010 03:57 PM

Quote:

Originally Posted by Yoyizit (Post 434841)
No.
The arctan of 4/3 is 53.1 and the arctan of 3/4 is 36.9.
This totals to 90.0.
The remaining angle must then be 90.0.

3" out of 12' is a 1.2 error. This error magnitude may reflect ordinary effort, given the conditions you worked under. With extraordinary effort you might significantly reduce this error.

Surveyors, of course, would want much better, over a distance of 12'.
http://www.google.com/search?client=...UTF-8&oe=UTF-8

And you know anyone who can hold a drooping tape measure (perhaps two of them from two different directions at once) to within a tenth of an degree?

Sorry. Too many decades in the field dealing with this kind of error says it ain't gonna happen. :no:

Willie T 04-28-2010 04:00 PM

Quote:

Originally Posted by Starbuck II (Post 434805)
So is there any solution at all? is there anyway to fix this short of blowing it up & starting over?

It is really only a problem because of the steel fixtures. If you can get them out of the way, drilling in new ones in the existing columns would probably get things close enough.

It would shock you how many houses get built where the walls miss their intended relationship to the footings by as much as you are talking about here.

Starbuck II 04-28-2010 04:27 PM

Hmm,

but that would then place the post at the edge of the footing, not anywhere close to putting the roof load on the center of the footing so I would be afraid that the load could crack the concrete.

Also the anchors are fairly large inside the concrete so I would probably run into metal a few inches down.

any other approaches?

kwikfishron 04-28-2010 05:36 PM

Small deck, small roof, small footing, I’d be moving it, but that’s just me.

Starbuck II 04-28-2010 06:51 PM

moving what? the footing? the anchor point?
Please clarify


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