Post connection to the concrete foundation

[73RR]

This is mostly pointed at currently practicing Engineers and Architects and a few of the brighter GC's building post-frame structures. It may be a bit 'deep' for the casual reader.

Although I have been retired for some time, I still get industry related reading materials. One of the more interesting in this weeks mailbox is related to how to connect your laminated building posts to the foundation.
The National Frame Builders Association article discusses some new designs to simplify the post-to-slab/plinth connection and may be useful for those contemplating a new building. Pass it along to your EOR.

http://www.nfba.org/uploads/Rigid_Connections-Jan_2017_FBN.pdf

 

[readhead]

Interesting read. I have always thought that something like this would be better than placing wood in the ground. I have built similar brackets. I used a piece of flatbar on both sides of the base to restrain the post.

 

[kbs2244]

The resistance to uplift and the stress at the floor "hinge" point is one of the least recognized advantages of post construction.
Lift/settlement is resisted by the friction along the side of a well tamped hole.(Done correctly, no concrete needed. Look at the millions of power poles installed without concrete.)
The floor hinge weakness is resisted by the strength of the continuous post.
The cost and complexity of all that hardware is eliminated.

If you want a concrete floor in your pole building, the best sequence is to build it with a dirt floor.
Then form your floor at the outside of the poles and pour so the concrete surrounds the pole and will be under any interior walls.
At construction time you have the advantage of doing the pour inside.
It can be done in the rain or cold.

 

[lakeroadster]

Most of the major barn manufacturers offer these "column to slab" style connections as an option.

The resistance to uplift and the stress at the floor "hinge" point is one of the least recognized advantages of post construction.
Lift/settlement is resisted by the friction along the side of a well tamped hole.(Done correctly, no concrete needed. Look at the millions of power poles installed without concrete.)
The floor hinge weakness is resisted by the strength of the continuous post.
The cost and complexity of all that hardware is eliminated.

Well said. If the prospective buyer had issues with posts in the ground... build a stick building.

If you want a concrete floor in your pole building, the best sequence is to build it with a dirt floor.
Then form your floor at the outside of the poles and pour so the concrete surrounds the pole and will be under any interior walls.
At construction time you have the advantage of doing the pour inside.
It can be done in the rain or cold.

Warm climate, non expansive soils, yes this will work.

Depending on the use of the building, and the geographic location, frost heave can be an issue and thus the slab moves in relationship to the columns (poles). If you build the walls on top of the slab, and attach the walls to the columns, then the frost heave will try to lift the columns out of the ground.

But if the walls are designed as floating walls, this will not be an issue.

 

[matt_i]

Interesting. It would take some very precise placement of the rebar out in the field to make sure everything lines up, and ensure it isn't knocked out of line during the pour.

I did something vaguely similar in my build for inside corners supporting a header but I relied on epoxied anchors.

The general idea was to use the knife plate idea, heavy steel and big bolts to gain as much friction as possible without crushing.

It was kind of a pain for 2 columns, a whole building would get a little tiring

 

[kbs2244]

Thanks for the details, lakerodser.
I have just seen 1/2 Cellotex used around the pols as a spacer to allow slab movement in my area.
But these were unheated equipment storage buildings.

 

[tlmartin84]

Very interesting..........

Mine is a hybrid design that I designed myself. Mine had movement until I place the steel truss on, once it was up everything is nice and snug.

View media item 44405
This one shows the location for the anchor bolts I use 4 per column/plate. I had to make plywood templates and fasten them to the forms to keep the bolts in alignment.

View media item 42965

 

[ard]

I just go with what the guys at Home Depot recommend....

 

[billgreenwood]

It was recommended by morton to put the building on top of the slab due to the rocky conditions of the subsoil. I ended up not going with morton for budget reasons, but I did use their idea for the brackets.

I used sturdi-wall drill set brackets for my building. I went with the drill set instead of wet set because I didn't want to have problems with having them set wrong. The bracket is bolted to the slab using 5/8x6" concrete bolts. The post is held in the bracket by two 10" through bolts and two 2" lag screws on each side of the pole.

Overall I am very happy with the quality and "performance" of the brackets. I put my building up as a DIY project and learned a few things along the way. I still have to put the through bolts in but even without them the poles have not moved at all with the lag screws holding them in place.

https://www.permacolumn.com/drill-set-models




Sent from my SM-G920V using Tapatalk

 

[bjcouche]

They used the same type of brackets to install my posts to my 8' tall concrete wall. One problem with these is that they don't have a proper brackets for corners. They have two L brackets that you are supposed to use. Unfortuneatly they don't make a left and right version, so when you drill the bolt holes for one bracket, it directly crosses the bolt holes for the other. I called the bracket manufacturrer and they said to just drill the bolt holes at a 45 degree angle so they wouldn't interfere... Looks like ****... The other problem was that the PE that designed the building didn't know that the concrete bit that is used to drill the anchor bolt holes cannot drill through the rebar he had placed in the wall. If you build with these brackets have the bolts set in the concrete before the pour, DO NOT let them try and drill holes for concrete anchors later.
Brian

 

[billgreenwood]

They used the same type of brackets to install my posts to my 8' tall concrete wall. One problem with these is that they don't have a proper brackets for corners. They have two L brackets that you are supposed to use. Unfortuneatly they don't make a left and right version, so when you drill the bolt holes for one bracket, it directly crosses the bolt holes for the other. I called the bracket manufacturrer and they said to just drill the bolt holes at a 45 degree angle so they wouldn't interfere... Looks like ****... The other problem was that the PE that designed the building didn't know that the concrete bit that is used to drill the anchor bolt holes cannot drill through the rebar he had placed in the wall. If you build with these brackets have the bolts set in the concrete before the pour, DO NOT let them try and drill holes for concrete anchors later.
Brian

I have the same L brackets on my corner poles. Instead of using the through bolts I just got some 3/8x2.5" lag screws and put them in opposite holes (one high/one low). I also had the issue of the rebar getting in the way of the drill bit. Some of the brackets ended up twisted a tad, but I was ok with it.

Sent from my SM-G920V using Tapatalk

 

[kbs2244]

I have posted this before, but this is the best pole construction book I have found.


http://www.pole-barn.info/pole-building-construction.html

 

[lakeroadster]

It was recommended by Morton to put the building on top of the slab due to the rocky conditions of the subsoil.

That's because they want to use a Bobcat with an auger to drill the holes for the columns... which doesn't work in rocky soils. Structurally posts in the ground would be a much stronger design... and a mini excavator would have worked for digging the holes.

The other problem was that the PE that designed the building didn't know that the concrete bit that is used to drill the anchor bolt holes cannot drill through the rebar he had placed in the wall.

I doubt this. The PE knew that re-bar cutting concrete bits are readily available. Whoever did the installation didn't follow the specifications.

This should have been caught by the building inspector and rejected during final inspection.

I have the same L brackets on my corner poles. Instead of using the through bolts I just got some 3/8x2.5" lag screws and put them in opposite holes (one high/one low).

If the design drawings call for a through bolt, use a through bolt. Lag screws into a piece of wood are an inadequate substitute for a through bolt.

This too should have been caught by the building inspector and rejected during final inspection.

 

[matt_i]

At the corner you probably should counterbore the holes slightly from the outside, enough to hide the bolt-head and then use a SAE washer in the counterbore.

That doesn't eliminate the issue of the identical brackets likely having the holes at the exact same height so the thru-bolts would interfere with one-another. One would either have to use a spacer on the concrete side or drill new holes on the other side (ideally they would come in a corner-set as you mentioned, pre-designed to eliminate this very condition)

 

[AZ Pete]

The resistance to uplift and the stress at the floor "hinge" point is one of the least recognized advantages of post construction.

Lift/settlement is resisted by the friction along the side of a well tamped hole.(Done correctly, no concrete needed. Look at the millions of power poles installed without concrete.)

However if there is significant uplift on the power pole, as when they are placed lower than the two adjacent poles, down guys are engineered into their placement.




Sent from my iPad using Tapatalk

 

[billgreenwood]

That's because they want to use a Bobcat with an auger to drill the holes for the columns... which doesn't work in rocky soils. Structurally posts in the ground would be a much stronger design... and a mini excavator would have worked for digging the holes.




If the design drawings call for a through bolt, use a through bolt. Lag screws into a piece of wood are an inadequate substitute for a through bolt.

This too should have been caught by the building inspector and rejected during final inspection.

As far as augering the holes goes, I understand they would want to do it the easiest way. I also understand that doing something other than their normal practices passes extra cost along to me. I have attempted to dig holes in my yard for other projects and have encountered large individual rocks as well as expansive shelves of rock.

In regards to the lag screws, I did not want to deal with counter sinking the bolt heads into the pole in order for my metal siding to be flush to the pole.

I know I will get some flak for this but I live out in the county so there are no inspections or permits required. That being said, I do my projects as safely and within codes as I can. I know some things are not done to code to a T, but I would not do something that would put my family in harms way.


Sent from my SM-G920V using Tapatalk

 

[73RR]

As far as augering the holes goes, I understand they would want to do it the easiest way. I also understand that doing something other than their normal practices passes extra cost along to me. I have attempted to dig holes in my yard for other projects and have encountered large individual rocks as well as expansive shelves of rock.

In regards to the lag screws, I did not want to deal with counter sinking the bolt heads into the pole in order for my metal siding to be flush to the pole. I know I will get some flak for this but I live out in the county so there are no inspections or permits required. That being said, I do my projects as safely and within codes as I can. I know some things are not done to code to a T, but I would not do something that would put my family in harms way.


Sent from my SM-G920V using Tapatalk

A good option for this concern is to use a carriage bolt. The short-round head should not interfere with the siding.
And, for those concerned with the shear strength of 'common' carriage bolts, you can always use a larger diameter.

 

[Falcon67]

Anybody replicating the recommended deal in the OPs post note that the hole schedule in Figure 12 of the PDF has A and B reversed - as far as I can tell.

 

[lakeroadster]

As far as augering the holes goes, I understand they would want to do it the easiest way. I also understand that doing something other than their normal practices passes extra cost along to me. I have attempted to dig holes in my yard for other projects and have encountered large individual rocks as well as expansive shelves of rock.

In regards to the lag screws, I did not want to deal with counter sinking the bolt heads into the pole in order for my metal siding to be flush to the pole.

I know I will get some flak for this but I live out in the county so there are no inspections or permits required. That being said, I do my projects as safely and within codes as I can. I know some things are not done to code to a T, but I would not do something that would put my family in harms way.


Sent from my SM-G920V using Tapatalk

How good is the lateral bracing on your building? I thought of you today when I saw this... http://www.garagejournal.com/forum/showthread.php?t=353084