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hidden post anchors?

sleepydad's picture

hidden post anchors? (post #192821)

sleepydad on Thu, 08/26/2010 - 05:53
in

I was planning on using auger (18”) and pouring 48” up to grade.  Then using 12” block to come up to 48” and finish it off with a cap.  This should leave me with a ledge for a thin stone veneer on the pier.

I need to anchor 2 8”x8” oak posts on top of the pier.

Would like something that is hidden from view?  Anybody have any recommendations on hidden post anchors?

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I have a bunch of them around (post #192821, reply #1 of 11)

by DanH in reply to sleepydad [original] on Thu, 08/26/2010 - 06:16

I have a bunch of them around somewhere, but I can't find them.


This country will not be a permanently good place for any of us to live in unless we make it a reasonably good place for all of us to live in.  --Theodore Roosevelt

yes I know (post #192821, reply #5 of 11)

by sleepydad in reply to DanH [original] on Fri, 08/27/2010 - 06:41

I was at your place and took them.  jesh you need to do some cleaning because your place was a mess.

Answer depends a lot on what (post #192821, reply #2 of 11)

by rdesigns in reply to sleepydad [original] on Thu, 08/26/2010 - 07:18

Answer depends a lot on what the posts will be expected to do:  Will they need to resist wind uplift? Do you really want the oak to contact the concrete pier? Will this be inspected? (Not that un-inspected work should be sub-standard, but some BI's tend to have tunnel vision that only allows for a very limited variety of applications.)

pictures are worth a bunch or words (post #192821, reply #4 of 11)

by sleepydad in reply to rdesigns [original] on Fri, 08/27/2010 - 06:39

Will it be inspected yes.

I have permits/plans and red stamps so yes it's all on the up and up so far.

I have never done this type of construction so I'm on new ground.  but that being said I have done some timber framing so I'm comfortable with the idea of doing the work myself.

the first attached just show what I was shooting for... yes I know it's not finished.

I have the white oak logs and I need to line up a lumber grader so I can use the beams we cut but once that is out of the way it should be pretty easy.

I would think the lumber direct contact wouldn’t be a problem 48" up from grade? white oak is considered resistant?  I could imagine some ways to get the timber up off the pier if need be.

I was planning to cut a narrow mortis with my chain mortise and then drill holes in the 1/2" strapping.  counter sink some 1/2" galvanized bolts and cover after inspection.

so maybe there is an easier way or a premade bracket but I'm guessing because I'm cutting my own 8x8 beams I'll have to fabricate everything myself?

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Often a bracket is made to go (post #192821, reply #3 of 11)

by Clewless1 in reply to sleepydad [original] on Fri, 08/27/2010 - 05:41

Often a bracket is made to go up inside the post. If there is uplift loads you'll need to have a hole in the bracket to install a bolt. Then plug your bolt holes if you don't want the bolts exposed. The bracket is a piece of rebar, a plate for the post to sit on and then a 'blade' that goes into the post.

There ain't NO free lunch. Not no how, not no where!

take a look (post #192821, reply #6 of 11)

by sleepydad in reply to Clewless1 [original] on Fri, 08/27/2010 - 06:46

I posted a reply with more detail on what I was thinking.  I was just wondering if there was something pre-made that might make it easier.

I think I might go spend some time with northern lights timber framing...(minneapolis,MN)  I might have to pay Clark Bremmer for some design work.  the city I live in is pretty stringent on stuff.

    Any reason you (post #192821, reply #7 of 11)

by JAlden in reply to sleepydad [original] on Fri, 08/27/2010 - 11:09

 

 

Any reason you couldn't use a round steel pipe? It's a lot easier to bore a round hole in the bottom of the timber than the chainsaw slice.

If you need to pin it for uplift, use a square steel tube (with holes) sized to fit in a round hole.

 

 

well (post #192821, reply #8 of 11)

by sleepydad in reply to JAlden [original] on Sat, 08/28/2010 - 05:49

That would work.. could actually use a square tube and just drill the hole a bit oversized.

I have one of these(see Attached ) so making a slot in the end of the timber will be a piece of cake.  clamp it to the timber and you get a nice squared slot.  with a drill I might wander around a bit; especailly in end grain.

the flat bar or square tube would work pretty much the same.  square stock might be a bit cheaper.  but it's only 2 pieces of steel.

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I'd give consideration to (post #192821, reply #9 of 11)

by MarkH in reply to sleepydad [original] on Sat, 08/28/2010 - 09:02

I'd give consideration to using a steel column and box it in with oak, instead of using an 8x8. 

Knife Plates (post #192821, reply #10 of 11)

by Ron_Trebbi in reply to sleepydad [original] on Sun, 08/29/2010 - 05:48

 

Clewless gave you good advice.  We do this concealed detail all the time and call it a knife plate.  Your chain mortise looks like exactly the right tool for it.  The knife plates are typically a piece of ¼” steel plate with two holes in it for thru bolting the plate once it’s in place inside the heavy timber.  This detail works well for connecting the timbers to the beams as well.

Two details to consider:

In the column / pier connection, the plate would be cast into the top of the pier and should have shoulders to support the bottom of the plate.  I would typically hold the plate an inch off the finished surface of the pier to keep water from wicking into the end grain of the post.  Snow is not much of an issue for us so you might deal with the stone wood contact issue a little differently.

For though bolting, we generally use all thread and a Forschner or really large paddle bit to cut a recessed hole the size of the washer and the depth of the washer and nut on each side of the plate.  It looks very clean when finished and is the same on both sides of the member rather than having a carriage bolt head on one side and the nut on the other.  We generally don’t plug the holes.  My feeling is it’s like an architectural grade, concrete pour with exposed snap tie dimples.

Let me know if you need some typical knife plate details and I’ll email you a couple from one of our recent projects.

Good Luck

RON

Ronald G. Trebbi

Architect  /  General Contractor

TREBBI CUSTOM CONSTRUCTION LLC

Award Winning Design and Construction of Residential and Light Commercial Renovations and Additions

Probably the easiest (post #192821, reply #11 of 11)

by davidmeiland in reply to sleepydad [original] on Sun, 08/29/2010 - 13:21

is to use a Simpson CPS base.... which is nothing but a piece of plastic that serves to protect the bottom of the post from moisture. The detail relies on a piece of all-thread or rebar epoxied into a hole drilled up into the bottom of the post. Attached detail photo shows the plastic base and the rebar stub waiting for a 6x6 post to be installed. You get pretty good uplift values from this if you follow the instructions. You could probably make your own base for your 8x8s.

We have also done the knife plate detail a number of times. I usually have a welder make the bases and then get them hot dip galv'd. In the second photo you can see the prep for this, and one of the bases is barely visible in the lower right corner, already attached to the concrete. After the post is set we drill from the side and install bolts thru the metal. If you have a chain mortiser you're ahead of the game.

You probably need to know the engineering values required and have the right method spec'd for you.

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