Use of Simpson Strong Tie Post Brackets

[Jjoness4]

Some time ago I posted about a building project the I am coordinating with a church camp in East Tennessee.  We had planned to use 7 inch posts for the construction and the project has a very limited budget.  I had a few 7x 7 inch posts already cut and was going to cut more to finish the project.  The structural engineer specified Simpson Strong Tie post brackets to attach the posts to an existing 5 inch thick concrete slab.  I was flabbergasted to find out that the 7 inch Simpson brackets are nearly $70 each.  The nominal 6 inch bracket (actual size 5 1/2")  which is very common is about $17.00 each at Lowes.  Now I am thinking about dropping back to 6 by 6 posts and beams for the project.  The engineer says that will work.  My question:  What are you guys using to attach larger posts sizes to concrete slabs.  Making you own??  I really would like to stay with the larger posts because it will just have more eye appeal, beefier. 

[Ljohnsaw]

If the engineer says that the 6x6 would be ok, what about trimming the end down to the nominal size?  Then you could make a skirt out of 1" board to cover the bracket.

[ChugiakTinkerer]

Is this something that needs a bracket, or can you use a Timberlinx?

http://www.timberlinx.com/cat_a475.html

These run $28 a piece and work with any timber.  Attach to a anchor bolt and finish it with a dowel in the hole so it looks from the outside like traditional joinery.

[Jjoness4]

Is this something that needs a bracket, or can you use a Timberlinx?

http://www.timberlinx.com/cat_a475.html

These run $28 a piece and work with any timber.  Attach to a anchor bolt and finish it with a dowel in the hole so it looks from the outside like traditional joinery.

Does the Timberlinx provide any standoff support to get the end of the post up off the slab to prevent rot.

If the engineer says that the 6x6 would be ok, what about trimming the end down to the nominal size?  Then you could make a skirt out of 1" board to cover the bracket.

This may be the approach I take.  Just a little more prep labor for the bottoms of the posts.

Thanks guys for your input.

[Don P]

This is another way if you have metal fabbing capability. The bottom plate with J hooks is embedded in the concrete. The knife plate and square tube is secured to the post. Stand up, drift around to correct location and field weld the post to the plate in the concrete. This gives you a standoff and the ability to drift around to perfect alignment. The engineer can specify knife plate dimensions and hole pattern. I've field drilled through post and plate once it is all down as well.

[Brad_bb]

Using Timberlinx, which is a good way to go to be more precise as you epoxy them into an existing foundation.  This allows for precision as opposed to brackets that are "wet set" and end up moving on you.  I did the Simpson straps once and they moved and we had to bend them to get them on the posts.  It was ugly. 

To separate the timber from the concrete make a 1/4 inch plexiglass plate that is 1/2 inch smaller than the timber(so it's not visible), with a hole in the center for the timberlinx.  Use 4 deckscrews or stainless screws to install the plexi on the post bottom.  You have to drill and countersink the 4 screw holes.  It's cheap and easy.

[Jjoness4]

This is another way if you have metal fabbing capability. The bottom plate with J hooks is embedded in the concrete. The knife plate and square tube is secured to the post. Stand up, drift around to correct location and field weld the post to the plate in the concrete. This gives you a standoff and the ability to drift around to perfect alignment. The engineer can specify knife plate dimensions and hole pattern. I've field drilled through post and plate once it is all down as well.

I wish I had that metal fabrication capability but I don't.  This is a neat way to anchor a post however.  I have an existing slab but the bottom plate could be attached with wedge head bolts into drilled holes.  The ability to move the plate and do field welding would do a great job but by the time I had someone fab up the bracket and then come and do field welding with a portable welder I can go with the Simpson tie, even the expensive ones.  All Simpson ties have an oblong hole in the base to allow for some adjustment before tightening it down to the slab.

Using Timberlinx, which is a good way to go to be more precise as you epoxy them into an existing foundation.  This allows for precision as opposed to brackets that are "wet set" and end up moving on you.  I did the Simpson straps once and they moved and we had to bend them to get them on the posts.  It was ugly. 

To separate the timber from the concrete make a 1/4 inch plexiglass plate that is 1/2 inch smaller than the timber(so it's not visible), with a hole in the center for the timberlinx.  Use 4 deckscrews or stainless screws to install the plexi on the post bottom.  You have to drill and countersink the 4 screw holes.  It's cheap and easy.

Using the plexiglass at the base of the post is a neat idea.  I have a fairly large sheet of scrap plexiglass which would make a lot of post bottom covers.

[Magicman]

Are the bottoms of the wooden posts going to have proper ventilation for drying if Plexiglas is used as a spacer? 

[Don P]

I usually rout a + in the post bottom with a 1/4" router bit to help, you could put some grooves in the plexi too I guess. On the last set of posts I did I used pieces of Trex, it has some texture but I'm not sure what its compressive strength is. Borate would help too.

For metal fabrication, cast the net, someone in that church has got to have those skills.

[Jjoness4]

Are the bottoms of the wooden posts going to have proper ventilation for drying if Plexiglas is used as a spacer? 

MM. Good point on the ventilation.  I have some porch columns on the front of my house that are decorative, that are made of redwood.  They are now 45 years old and are still  in great shape at the base.  They have a redwood base that has dadoes ( as per Don P comment) cut in the bottom of the solid base for ventilation.  These posts are box design and thus are hollow.  They breathe all the way to the top. 

On the camp building, I have decided to use the 6 inch nominal Simpson bracket and alter the bottom of the 7 inch post to fit the bracket.  I will be using 3/8', 4 inch long wedge anchor bolts to attach the bracket to the slab and a lot of care chalking out layout lines to make sure it all lines up. 
Thanks for all your input.

[florida]

The brackets get larger and are made with heavier steel every time you go up a dimension. I used some 8" x 8" ones on a house a few months ago that were $117.00 each. I'd certainly use the 6" X 6" if the engineer approves.

[Jjoness4]

Now another question, same project, different issue.  We are not using timber frame techniques ( ie mortise and tenon joinery.  I have not run this by the structural guy I was planning to use half lap joints to join the beams to the top of the posts and then to use 8 inch TimberLok screws through the half lap and well into the top of the post.  Sketch shows 7 inch posts but the dimensions will change but the idea is the same.  I wonder about uplift strength but I have built several sheds over the years with about the same configuration and the roofs stayed on with 60 penny nails not TimberLok screws.   I will run this by the structural guy but just wanting some forum input as well.  I could use a scab tee plate which will probably be the engineers requirement.

[ChugiakTinkerer]

The structural screws (Timberlok, etc) usually hold in tension much better when the screw is anchored across the grain.  It really depends on the wood, but in my experience you'd have a stronger screw connection with a Timberlok angled in at 45 degrees than you will with one driven vertically into the post.

As far as uplift goes, Timberloks are approved for rafter tie-down connections.  Fastenmaster has a video at http://www.fastenmaster.com/videos/timberlok-rafter-tail-truss-top-plate-connection.html

For the joint you have shown I would consider securing the right beam first with a timberlok on either side, angled at 45 degrees.  I'd then secure the left beam by driving two (?) Timberloks in vertically.  A single Timberlok has an uplift design load of 420 lbs in SPF and 620 lbs in Southern Pine.  It's about half that if the point end is aligned with the grain.  With four in that connection it ought to be adequate but some actual engineering work may be appropriate here.

[canopy]

It's not clear to me how grooving the bottom of the post solves any moisture entrapment concerns. With no grooves, the entire post base is flush against the pad. With a + routed in the bottom, there are now 4 smaller surfaces of the post flush against the pad. How is this solving anything?

I like to melt beeswax into the end grain.

[Jim_Rogers]

Creating a half lap directly over a post is not the best. You're asking your beams to be as strong as they can be (supporting your load) and then you cut half of them away.
If you need to have a joint over a post it would be better to support that joint with a bolster.



 

Jim Rogers

[Jjoness4]

Creating a half lap directly over a post is not the best. You're asking your beams to be as strong as they can be (supporting your load) and then you cut half of them away.
If you need to have a joint over a post it would be better to support that joint with a bolster.



 

Jim Rogers

Jim, We don't possess the skills to do an intricate scarf joint with a bolster as you suggest.  Maybe one of these days those skills will be acquired but for now the half lap is the best we can do.  With the full beam depth resting on the post and tied together with multiple  long timberlok screws at a angle as suggested by Chugiak and the beam span being only 10 feet, I think it will work for a shed type structure with low loading.  Jim thanks for your input.  I want to learn to cut a scarf joint like you do so well.

Chugiak,  thanks for the references and the video link.  They were helpful.  I will get the structural guy to look everything over before we execute.

It's not clear to me how grooving the bottom of the post solves any moisture entrapment concerns. With no grooves, the entire post base is flush against the pad. With a + routed in the bottom, there are now 4 smaller surfaces of the post flush against the pad. How is this solving anything?

I like to melt beeswax into the end grain.

Canopy,  I see your point.  I am planning to use the galvanized Simpson Strong Tie which holds the end of the post about an inch away from the concrete.  However anything that can be done to protect the wood long term should be done.  These posts will be a mixture of red oak, white and southern yellow pine, all prone to rotting if debri gathers around the base over time and it stays damp or wet.  I think the word groove is probably a misnomer.  I think it has to be a sizable dado to allow air flow and drainage to have any benefit.  But as you say you are diminishing the bearing area and increasing the chance that the end grain crushes under compression.

[Dave Shepard]

I think Jim's pic was to show the bolster, not the scarf. Bolsters were common in heavy timber mills where there was little to no traditional timber frame joinery.

[Jim_Rogers]

I think Jim's pic was to show the bolster, not the scarf. Bolsters were common in heavy timber mills where there was little to no traditional timber frame joinery.

Yes please disregard the scarf joint in the above timbers.

Jim Rogers

[Jjoness4]

I think Jim's pic was to show the bolster, not the scarf. Bolsters were common in heavy timber mills where there was little to no traditional timber frame joinery.

Yes please disregard the scarf joint in the above timbers.

Jim Rogers

I think Jim's pic was to show the bolster, not the scarf. Bolsters were common in heavy timber mills where there was little to no traditional timber frame joinery.

Oops!  I totally missed the point.  Thanks guys for the clarification.  I still want to learn how to do a scarf joint. :P

[Phil H.]

Creating a half lap directly over a post is not the best. You're asking your beams to be as strong as they can be (supporting your load) and then you cut half of them away.
If you need to have a joint over a post it would be better to support that joint with a bolster.



 

Jim Rogers

Jim,

Would a butt joint and spline combo (pegged) also work instead of the bolster?  Any idea on the strength difference?

[Jim_Rogers]

Creating a half lap directly over a post is not the best. You're asking your beams to be as strong as they can be (supporting your load) and then you cut half of them away.
If you need to have a joint over a post it would be better to support that joint with a bolster.



 

Jim Rogers

Jim,

Would a butt joint and spline combo (pegged) also work instead of the bolster?  Any idea on the strength difference?

That's an engineering question, that I can't answer. Sorry.

Jim Rogers

[Brad_bb]

Are the bottoms of the wooden posts going to have proper ventilation for drying if Plexiglas is used as a spacer?

As I wrote the plexi is 1/2 inch smaller than the post.  But this should not be a concern as end grain is typically sealed with Anchorseal.  The timber should be drying out the sides of the timber.  I'm assuming that we're talking about timbers that are "indoors".