Pole Outbuilding Potential for Structural Failure

Trimmer · Jul 21, 2017

I'm a trim/finish carpenter. My crew started work on a ceiling today for a friend of mine on his outdoor pavilion. After looking at it, we came to the conclusion that the design was seriously flawed and was just waiting to fall over in a storm. We are trying to come up with some suggestion on how the building can be fixed. As built, the entire structure shakes just pushing on the support beams.

(Pictures attached, I don't know how to include them in the post itself/provide captions).

Specs: 20'4"x30'. The foundation wall is 6" thick and about 3-4 feet deep on a footer (Not absolutely sure on the wall height as it is backfilled already).

Roof is supported by four 8x8 treated posts, that rest on the footing and are notched 2" over the edge of the wall. They have two angle brackets on either side of the post from 1/8" steel. Each bracket has a single bolt in the 6 inch foundation wall (which as you can see from the pictures is a drive in anchor that broke through the wall). It has a single leg bolt and a screw into the post. So to be clear, there is a single bracket on either side of the post at the bottom of the wall and then a single on either side at the top of the wall. The post is just sitting on the footing, not on a concrete pier. There are no angle braces.

Bottom of the beams are 8' above a to be finished floor.

It currently has no truss/hurricane anchors. The trusses are simply toenailed.

The owner had pictures of a project in California of the same style, but when I looked it up, it was built with steel posts set on 6' concrete piers.

Any thoughts short of replacing the posts with steel posts on piers?

TommyK · Jul 21, 2017

At a minimum you need diagonal bracing at each post in each direction.

bbirder · Jul 21, 2017

The contractor that put that up should be shot. U can try installing guy wire braces diagonally between posts and crossing the ceiling but can't guarantee it.

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bbirder · Jul 21, 2017

Although mine is a steel bldg this is what I meant. Use some 1/4" galv cable from top to bottom on one side and criss cross some cables across your ceiling. Should help stabilize it

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Ironcrow · Jul 21, 2017

The wood columns end in dirt? Buried in the pad? Since these columns need to be AT LEAST heavily revised you might as well take them out and replace with...steel or concerte columns...

BADSIX · Jul 21, 2017

A friend of mine has almost the same setup ,only he framed 4' from each corner and sheeted it with 5/8 siding. makes a nice place to put things and still leaves it open his is very sturdy. toe nailed to the top plate was the only way it was done before hurricane clips. I don't think the clips are any better other than making you wallet lighter. the post thing is a little shady but if you frame out 4' on each corner you could anchor them down to the slab.
Jay D.

Trimmer · Jul 21, 2017

TommyK said:
At a minimum you need diagonal bracing at each post in each direction.

The owner was trying to avoid that (replicating the design he saw elsewhere) but that was our first recommendation. We thought maybe he could have a 1/4" steel U shaped wrap from top to bottom of the post and pour a pier around the post with steel reinforcement.

I'm just a trimmer, so I don't know if that would provide sufficient lateral strength. And it might be the same cost/labor as just replacing the whole post to begin with.

As far as the suggestion about the wires for support, its probably a good idea, but I know the owner won't like his fancy outdoor eating area with wires across it.

Trimmer · Jul 21, 2017

We are wrapping the trusses with cedar and putting in a vaulted wood ceiling. The inspiration was this pavilion by Gaylor Design.

Trimmer · Jul 21, 2017

Ironcrow said:
The wood columns end in dirt? Buried in the pad? Since these columns need to be AT LEAST heavily revised you might as well take them out and replace with...steel or concerte columns...

I kind of figured that would be the only real reliable fix that would leave the building with the external appearance that the owner wants.

bczygan · Jul 21, 2017

Here you go...

https://www.garagejournal.com/forum/showthread.php?t=353084

Bill

Trimmer · Jul 21, 2017

bczygan said:
Here you go...

https://www.garagejournal.com/forum/showthread.php?t=353084

Bill

That's the post that led me to the Garage Journal. Found it in a google search...

6768rogues · Jul 21, 2017

It needs diagonal braces to stop it from racking.
Also, it needs hurricane ties or straps to hold the roof down. An open building is more likely to blow away than an closed building. With the wind going through and over it, it resembles an airplane wing. The air has to go further to get around the roof going over than going through. That stretches the air and lowers the pressure. Low pressure on top and higher pressure on the bottom resembles an airplane wing and goodbye roof.
I am also concerned about the connection of the poles to the slab. Who knows if they have enough strength to resist pullout?

The Tool Tyrant · Jul 21, 2017

Well...well...well...looks like another fine mess caused by the 'Low Bidder'.

As mentioned above, there are a few different 'band-aid' fixes, but if this was mine, I'd do it right. You need to remove the 'moment' in both directions AND sufficiently anchor the building to the foundation to resist whatever uplift the building may have to endure (earthquake, tornado etc) As I said, if it were MINE, I'd sufficiently shore up the entire roof, leaving enough room to sawcut the slab around each post to allow a 24" auger access to auger at least (depending on soil conditions and frost line, if applicable) 6' below grade. Then I'd use 8X8X .250 wall square steel tube with a 12x12x1/2" base plate with 4 holes for 3/4" anchor bolts welded to the bottom and a Simpson column cap welded to the top. Install the 3/4"x 18" anchor bolts, with nuts on top and bottom. Be sure you have a minimum of 3" of concrete below the bottom of the anchor bolts. You will have to remove whatever roof sheathing required to gain access so you can lower the column down into the hole. Raise the column so the column cap contacts the bottom of the beam and bolt it in place. Plumb the post and brace as necessary. Form-up a box around the steel column, flush with the slab height, Using a roto-hammer, drill into the side of the slab to allow you to epoxy 4 (2 ea. side) short rebar dowels to tie the box-out to the slab. Pour the concrete, using a ******** to ensure all voids are filled. Sounds like a lot of work, but like I stated...this is how I'd do it if it were mine...and FWIW, I sleep VERY well at night. :beer:

theoldwizard1 · Jul 21, 2017

I like Tool Fool's answer !

Trimmer · Jul 21, 2017

Thanks to all for the recommendations. I think the best thing looks to be replacing the posts if the end product is to look like the inspiration and be structurally sound. That will be our recommendation then. We will see what happens. Even if we put up angled bracing, i think the 4 concrete anchors and 1/8" thick angle brackets holding each post to the 6in foundation wall is insufficient.

Bluedodge · Jul 21, 2017

A lot will depend on where you are Sir.
You mention California pictures. Southern Cal? Northern Cal?
Snowbelt regions in West Michigan or Western New York?
No (low) load area like Georgia?
High wind area like Vermont or Florida?

Where are you?

ard · Jul 21, 2017

+1 on lakeroadsters post- was thinking of that as I read. The very funny to find that was what led Trimmer here.

Good advice above- but at the end of the day, whoever builds it, owns the results. you touch it now, then you are on the hook. Unless you can properly engineer the retrofit, you take the risk.

Show the owner the other post/thread and pictures....

Ironcrow · Jul 21, 2017

Trimmer said:
I kind of figured that would be the only real reliable fix that would leave the building with the external appearance that the owner wants.

I know you said you didn't want to "re-column" it, but by the time you figure out diagonal bracing, add shear walls, large gussets, whatever it is likely to cost as much as replacing with steel columns AND be ugly too.

Trimmer · Jul 21, 2017

Bluedodge said:
A lot will depend on where you are Sir.
You mention California pictures. Southern Cal? Northern Cal?
Snowbelt regions in West Michigan or Western New York?
No (low) load area like Georgia?
High wind area like Vermont or Florida?

Where are you?

Northern Indiana, so it has to handle snow loads as well as high winds. Just before they put this up a storm went through that took down a tree right at the edge of the clearing for this place.

Trimmer · Jul 21, 2017

ard said:
+1 on lakeroadsters post- was thinking of that as I read. The very funny to find that was what led Trimmer here.

Good advice above- but at the end of the day, whoever builds it, owns the results. you touch it now, then you are on the hook. Unless you can properly engineer the retrofit, you take the risk.

Show the owner the other post/thread and pictures....

We definitely aren't planning on doing the repair. The contractor needs to fix it and they really need an engineer to do the design so they can have a long lasting safe structure.

n20junkie · Jul 21, 2017

How far down into the ground do those posts go? If they go down a good 4' then some 1/4 thick steel plates for the beam connection at the top will probably be fine. Post and beam can do a lot with proper connections.

If the main support posts only go down a few inches, then there are big problems.

bczygan · Jul 21, 2017

You need triangulation to transfer loads into the vertical columns. Wood columns are OK, but you need metal T shaped steel plates to connect the columns to beams on both lateral directions. This will give you the triangulation in the joints.

Then you need to connect the bases of the columns to the slab so no lateral movement occurs there.

And yes, an engineer to make sure the numbers work and to take responsibility. They can also give the owner the most cost effective solution that meets codes, whether it be a major or minor fix.

Bill

Mikeske · Jul 22, 2017

The easiest thing to do is do not touch it.

Musicinabottle · Jul 22, 2017

Red lights flashing all over the instrument panel.

ard · Jul 22, 2017

FWIW

I did something similar- large roof, just a post w no diagonals.

I fabbed 5x5 steel posts, -.25" wall, onto a 14" square 1/2" thick steel plate. 4 holes. 3/4" threaded J bolts place in concrete, formed with 24" sonotubes. 1/2 to 1 yard per hole, down 3-4 feet. Top I welded on a Simpson colum cap, like this:

So imagine a 5x5 post butted into the bottom of that...then a base with four 3/4" bolts into a mass of concrete.

Each of the 'joints'- the ground-to-post and the post-to-beam provide support, shear and uplift.

CJ7VFR · Jul 22, 2017

Trimmer said:
That's the post that led me to the Garage Journal. Found it in a google search...

The pictures in that thread speak for themselves. There is a right way and a wrong way to do this. Do it the right way, and it will stand for decades. Do it the wrong way and something like this might/can happen.

Physics is physics. You can't get around it.

Jim

Trimmer · Sep 3, 2017

Well, its been a while since I started this thread but I thought I would give the resolution to the problem in case anyone was interested. An engineer got involved because we said we wouldn't trim the building unless it was fixed. The contractor paid us to use the stamped engineered plans to fix the building and it is now a structurally sound pavillion.

What we did:

1. Dug out the base of the four posts. When we dug it out, we found that each post was anchored to the wall with just 4 bolts: Two brackets on each side of the post, with as little as 16 inches in between the brackets. Basically, this was a pivot point which greatly increased the instability of the original structure.

2. We added 2x10 treated boards to both sides of the posts, that ran bottom to top. We filled in the gap with 2x8 treated also running bottom to top (no splices or cuts). This was fasted with glue and spax screws.

3. We moved the brackets as far up and down the post as possible while still having good concrete to anchor into and added a third bracket in the middle so each post ended up with six anchors.

4. We added 1/2 rebar U's around the posts anchored into the foundation and filled the 24"x24" plus sized holes with concrete.

5. Added 1/4 inch steel T brackets to the inside and outside of the posts.

The building was good and solid at that point and we trimmed it out.

Mikeske · Sep 4, 2017

So now a the structure is sound and safe. You got to wonder what some folks are thinking of when they build stuff that is not safe or structurally sound. Good job bringing the building up but you got to wonder the cost as it probably doubled as it had to have all the rework to correct it.

ard · Sep 4, 2017

Nice job, looks great.

Any blowback from contractor or owner? Or did you get a (deserved)
'thanks'??

Trimmer · Sep 4, 2017

ard said:
Nice job, looks great.

Any blowback from contractor or owner? Or did you get a (deserved)
'thanks'??

Thanks. The contractor ended up saying he didn't know how to build pavilions and the owner was extremely grateful for the finished product. So I think everyone is happy now...

66cj225 · Sep 4, 2017

I thought it was pretty neat to evaluate a pavilion with all the garage lift talk that goes on this forum. Basically a pavilion is two 2 post lifts with a somewhat similar load in the air regulated by entirely different standards, the building industry and the industrial folk. It's kind of interesting to see how the two compare. Lift industry would just include snow load and wind loading in the safety factor where the building industry considers these as a given.

GMCGarage · Sep 4, 2017

Trimmer said:
I'm a trim/finish carpenter. My crew started work on a ceiling today for a friend of mine on his outdoor pavilion. After looking at it, we came to the conclusion that the design was seriously flawed and was just waiting to fall over in a storm. We are trying to come up with some suggestion on how the building can be fixed. As built, the entire structure shakes just pushing on the support beams.

(Pictures attached, I don't know how to include them in the post itself/provide captions).

Specs: 20'4"x30'. The foundation wall is 6" thick and about 3-4 feet deep on a footer (Not absolutely sure on the wall height as it is backfilled already).

Roof is supported by four 8x8 treated posts, that rest on the footing and are notched 2" over the edge of the wall. They have two angle brackets on either side of the post from 1/8" steel. Each bracket has a single bolt in the 6 inch foundation wall (which as you can see from the pictures is a drive in anchor that broke through the wall). It has a single leg bolt and a screw into the post. So to be clear, there is a single bracket on either side of the post at the bottom of the wall and then a single on either side at the top of the wall. The post is just sitting on the footing, not on a concrete pier. There are no angle braces.

Bottom of the beams are 8' above a to be finished floor.

It currently has no truss/hurricane anchors. The trusses are simply toenailed.

The owner had pictures of a project in California of the same style, but when I looked it up, it was built with steel posts set on 6' concrete piers.

Any thoughts short of replacing the posts with steel posts on piers?

The owner should have a serious discussion with the contractor and engineer of record.

ard · Sep 4, 2017

GMCGarage said:
The owner should have a serious discussion with the contractor and engineer of record.

Did you actually read the thread???

GMCGarage · Sep 4, 2017

ard said:
Did you actually read the thread???

Yes.

NUTTSGT · Sep 4, 2017

So looking at the pics and description, how far where the posts in the ground ? Maybe like 24" ?

johnnyradiant · Sep 4, 2017

Not knowing how to build a pavilion? Really? Not only is that evident even looking at a snap on a phone screen but one really has to wonder what does the original contractor really understand about structure especially in a wind and snow load region. I guess his 'structural' work is usually covered up with drywall, plywood or siding, cement or dirt? Or his structural work is normally geared more towards holding up a couple hundred pounds on a stair? The amount of remedial work needed to make it sound is so far off of what was provided in the first place can you even call the first attempt structural?

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matt_i · Sep 5, 2017

To the O.P. good job recognizing the fail in the structure. The property owner should take you out for a steak dinner.

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