Attaching large log posts to concrete piers?

oklalogdog · July 19, 2012, 07:30:31 PM

After cutting around 500 ERC logs and doing a bit of dozer work we are
ready to start on our log home. Problem is I am going to be attaching
some large round posts to concrete piers. These posts will be at
least 20" at the base and some will be 18' tall.

I have scoured the internet and found a number of ways to do this but
anything with uplift protection seems to be unsightly such as with
straps on the outside and the like. In our area "Tornado alley" we
have some very strong storms at times so I will need some uplift
protection with whatever method I decide to use.

My question to the forum is this. Does anyone know of any methods to
attach these posts that would be hidden from sight and still supply my
needs?

I have thought of 2 pieces of steel plate welded together to make an
upside down "T" with the base of the T attached to the pier and then a
single plate going up through the center of the log post and pinned
with through bolts. Any help would be appreciated

logman · July 19, 2012, 08:28:52 PM

Check out Timberlinx. We used them all the time to hold down posts on timber frames.

oklalogdog · July 19, 2012, 08:50:33 PM

Thanks Logman for the reply - I will do that.

jander3 · July 20, 2012, 06:47:27 AM

For the Stump Ranch, I added some rebar to the piers and drilled matching holes in the bottom of the log piers.

thecfarm · July 20, 2012, 06:52:56 AM

Going to take us along for the build? ;D Good luck.

jander3 · July 20, 2012, 06:55:35 AM

If the posts are vertical and will support a ridge or porch or something else, attach with a screw jack to account of settling. The base of the post is wrapped (with metal) to hide the jack, but allow access to crank it down as the building settles.

Here is a source for screwjacks
http://www.loghelp.com/c-40-log-home-screw-jacks.aspx

Jim_Rogers · July 20, 2012, 07:11:47 AM

At a guild raising event, I saw this guy cut a slot into the bottom of some posts with a jig he made to hold his chain saw bar at the correct position.

Here is a shot of the upside down "T" that he was fitting into each post:

Here is a picture of the post standing and welded:

They set the plate in the concrete and under the plate is another similar bar going down with "J" hook attached to it and wrapped around the rebar.

This barn is in the mountains of NH and not likely to see strong winds.
But that was the method they used when they did that back in 2003.

Jim Rogers

oklalogdog · July 20, 2012, 07:40:00 AM

"Stump Ranch" - your cabin looks great - thanks for the photos.

oklalogdog · July 20, 2012, 07:45:31 AM

"Jim" - your photos of the upside down T are very similar to what I had envisioned. I could make the upright portion a little larger and use 4 bolts. That should provide about as much strength as you could realistically get.

Thanks for the pics.

oklalogdog · July 20, 2012, 07:54:34 AM

"Jander 3" Thanks for the link. I have two neighbors "brothers" who built log homes here about 27 years ago. One of the brothers built stick homes for a living. The homes were built out of native ERC and the logs sawn into 'D' logs. They left space for settling on the first home but there never was any settling. He showed me a few weeks ago where he had left the settling space above a window and the space is still there.

The second brother didn't leave space for settling and has never had any problems. The only thing I can think of is that ERC dries pretty fast and after the logs have been cut for a couple of years and in our climate here in western Oklahoma - maybe they are done and have already shrunk as much as they are going to.

jander3 · July 20, 2012, 11:59:26 AM

Green logs will shrink about 3/4" per foot of wall height. Logs dry and settle in about 3 years. If building with green you need settling space.

Ironwood · July 20, 2012, 08:16:15 PM

I like the slot the guy cut and the method, BUT I would do two things, larger washer/straps at the bolt location in the log, AND make them from stainless ALSO move the log UP to give some AIR under even if you had to make two "T" flanges, one for concrete contact and one for wood contact. You can forge the stainless washers and such so it looks "not stainless" but retains the rust proof nature.

Ironwood

oklalogdog · July 21, 2012, 10:43:24 AM

"Ironwood"

I believe I understand what you are saying about the double "T" but am a little fuzzy on the larger washers/straps part. Sounds very interesting but could you explain a little further?

Ironwood · July 21, 2012, 06:59:09 PM

Well, the only weakness is "pull out" from the wood contact (minimal), so if you can stand the look, increase contact area of the fastening by:

1. using a strap to connect multiple bolts (vertically), now the wood in between the bolts is helping hold to, OR

2. still have the bolts/nuts individual, but increase the surface size of the washer contacting (holding/compressing), countersink with a forsner or something and then a big stainless washer/nut subsurface.

hope that helps, Ironwood

oklalogdog · July 21, 2012, 10:34:34 PM

Ironwood - so basically you are talking about steel straps outside the log and welded to the base with bolts going through the straps and the steel tenon in the center of the log- or just larger washers on the outside of the log and behind the head and behind the nut of the bolts. The former obviously would give more strength. If it's a fair question - What would you do if it was your home?

Ironwood · July 21, 2012, 10:52:04 PM

You dont need the outer straps welded to the "T" (s), the bolt will provide that connection (thru the metal tenon inside the log). I would use the double "T", with an air gap to let the wood breathe and stay dry at the joint. Remember that will be the "draining" point of anything that contacts the upper and flows down. I would lightly forge the stainless straps to give them character and not so shiny color, 1/4 x 1 1/2" flat bar, you could even hammer them to a radius similar to the outside of the log, over their length for more contact, OR router in a "flat" on the log to mate them and then just leave them flat. I have "floated" numerous columns on either large stainless lags (making a foot, and an air gap), OR with aluminum flat plate, isolating the masonary/concrete from the wood fibers. Both applications have situatons where driven rain can gain access to the lower joint, thus the need for the air gap.

Ironwood

oklalogdog · July 22, 2012, 09:39:55 AM

Good info here folks - thanks a lot!

Jim_Rogers · July 22, 2012, 10:00:30 AM

The frame I showed was enclosed so those posts weren't exposed to rain.

But I believe they still put a piece of ice and water shield between the wood and the metal plate, with the sticky side up to secure it to the bottom of the post.
This was to prevent any moisture from entering the bottom of the post.

I know we did that on another frame.

Jim Rogers

thedoublejranch · August 15, 2019, 02:58:47 PM

Good information, I was just looking to do the same thing, but unable to find any info, will to the T plate, maybe a knife cut in the log with my chain saw. I have MIG welder, hypertherm plasma cutter, oxy acet and chop saw, will build my own. I was just thinking of having it set in the pier vs bolting to the top, otherwise, the plunge or knife cut and 2 large bolts is what I had in mind.

On another note, found an old snag on my back 40 I never saw before I had it comercially thinned which exposed it (could now see it) and cut it down to find gorgeous solid wood, its old growth ponderosa pine. Locals call it pitch wood or yellow wood, no buts, stains, nothing. I need to get this to a mill. ;D