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View Full Version : Attaching two 6" x 6'" posts ??



Ben Davis
07-27-2008, 8:58 PM
Hello... I'm running into somewhat of a quandary in a project that I'm planing out. I need to vertically extend the current posts / columns on my deck by about 6 feet. Has anyone attached two 6" x 6" end on end?

The project will be a pergola that covers the deck, so the load is actually minimal. There is vinyl railing that surrounds the deck to about 36" about the deck surface, and the posts extend to about 40" with a decorative cap on top. I don't want to tear up the deck too much to do this.

My current plan is to create a half-lap joint and bolt the two members together. I don't know what size bolts to use though... 5/8"? Any help would be great!

Bob Moyer
07-28-2008, 7:26 AM
I am looking to do the very same thing, with 4 x 4 posts; is this an application where one could use a pocket hole jig?

Brian Effinger
07-28-2008, 9:30 AM
If it were me, I'd set the posts on each other and attach them together with some sort of metal post cap, like a Simpson Strong-tie BC6 ( http://www.strongtie.com/products/connectors/bc.asp ), and then sleeve the whole thing with 1x material so that it hides the connection and ties the 2 together even better. I've never tried this before, but if seems like it would work.

Greg Cole
07-28-2008, 9:44 AM
The old timers that built timber frame structures did this all the time with a 1/2 lap scarf joint and some pegged the joint together with a dowel for good measure.
Here's an excerpt from a pretty reliable source, Tommy Silva, I'd say if it's good 'nuff for him......;) I looked for a pic to tag along but seemingly found none in a quick look round the 'net. But the joint looks about like a childs rendering of a lightning bolt as to the zig zag shape.

"About half the posts in here were five inches too short," says TOH's general contractor as he sets the saw aside. "They looked fine until we replaced the structure that would support the floor and started to lower jacks holding up the barn. That's when we noticed the problem." The old barn floor had been built on two levels no one is sure exactly why. But years of accumulated debris and patchwork repairs had hidden the step-down. To lengthen the posts, which will be visible once the barn is finished, Tom splices in additional sections of equally worn and aged timber salvaged from posts he's replaced in the garage below. He uses a half-lap scarf joint, a beveled zigzag that's fastened with construction adhesive and locked tight by the weight of the barn itself no hardware needed."

Might not be the answer for you, but it's much more aesthetically pleasing as compared to a galvanized Simpson Strong Tie product.

Cheers.
Greg

John Schreiber
07-28-2008, 11:38 AM
I thought that was very interesting, so I Googled around and found these pictures of a scarf joint on the web.

http://lh4.ggpht.com/_oq0xfNMtIF0/RxL5Rw3S0lI/AAAAAAAAA28/pdE1YNFQBGw/IMG_0975.JPG

http://www.colonialbarn.com/images/craftsmen.jpg

http://www.palomar.edu/WOODWORKING/Media/TF2000-11.jpg

http://www.trilliumdell.com/vocabulary/img/scarf_joint.jpg

http://www.wealddown.co.uk/images%20magazines/timber%20repair%207.jpg

http://farm4.static.flickr.com/3116/2610040771_895a218d6b.jpg?v=0

Lee Schierer
07-28-2008, 11:59 AM
This is a really good time to consult the local bulding codes for what you are attempting to do and maybe consult a P.E. for guidance of your particular situation. Without more details, you may be asking for trouble extending your columns. Buckling becomes a greater factor when the column gets longer and you would put tremendous forces on your joint if the column even starts to buckle.

Greg Cole
07-28-2008, 12:21 PM
I've seen these joints holding in barns that had no right still being upright, listing 25% to one side etc.... the joinery stayed intact but some of the roof leaking was the downfall. I don't think I'll be second guessing the guy I quoted earlier either.;)
And yes, do your due dilligence about building codes etc.

Greg

Tim Morton
07-28-2008, 1:06 PM
I think there is a big difference between extending something 5" and extending it 6 FEET. I think I would get a professional opinion on this one.

Clint Jones
07-28-2008, 1:21 PM
The old timers that built timber frame structures did this all the time with a 1/2 lap scarf joint Cheers.
Greg

Yes this would be the way to go.

Ken Garlock
07-28-2008, 2:08 PM
Hi Gents.

I found this site (http://sawdustmaking.com/woodjoints/scarf.htm) that discusses attaching timbers end to end. In particular it describes multiple types of scarf joints along with drawings.

Ben Davis
07-28-2008, 5:09 PM
I am looking to do the very same thing, with 4 x 4 posts; is this an application where one could use a pocket hole jig?

Bob: I don't think that pocket screw joinery would provide enough stabilization to the base of the column unless it were exceedingly short. I would really look to other methods.


If it were me, I'd set the posts on each other and attach them together with some sort of metal post cap, like a Simpson Strong-tie BC6 ( http://www.strongtie.com/products/connectors/bc.asp ), and then sleeve the whole thing with 1x material so that it hides the connection and ties the 2 together even better. I've never tried this before, but if seems like it would work.

Brian: I looked at the link above, and it does look interesting. My concern is that it is designed to place beams across the top of the post rather than secure two posts end-on-end. I did plan to hide as much of the joinery as possible with 1-by "casing" so to speak.


The old timers that built timber frame structures did this all the time with a 1/2 lap scarf joint and some pegged the joint together with a dowel for good measure.
Here's an excerpt from a pretty reliable source, Tommy Silva, I'd say if it's good 'nuff for him......;) I looked for a pic to tag along but seemingly found none in a quick look round the 'net. But the joint looks about like a childs rendering of a lightning bolt as to the zig zag shape.

I know what you're talking about. My concern is that the length of the joint required would be quite long.. probably 2 - 3 feet (!) in vertical length to make enough zig-zags. I didn't see this particular show though.



This is a really good time to consult the local bulding codes for what you are attempting to do and maybe consult a P.E. for guidance of your particular situation. Without more details, you may be asking for trouble extending your columns. Buckling becomes a greater factor when the column gets longer and you would put tremendous forces on your joint if the column even starts to buckle.

Lee: The two columns end-on-end actually act as two separate columns, so the "long slender column" problem is not a huge concern. But I agree, you try and limit the length of the column to 20x the maximum diameter. The other side of it is that the structure is not going to carry a significant amount of weight compared to the size of the columns.


Hi Gents.

I found this site (http://sawdustmaking.com/woodjoints/scarf.htm) that discusses attaching timbers end to end. In particular it describes multiple types of scarf joints along with drawings.

Ken: Thanks for the site! Quite interesting to read. It looks like most of those drawings are of beams. The same theories should apply for compression beams though.

-Ben

Andy Hoyt
07-29-2008, 12:12 PM
A scarf joint and half lap are entirely different animals. The only vertical scarf for this application is one that you probably don't want to attempt if you don't want to take the chance of eventually having to replace the lower (already installed portion) due to a fubar'd effort on your part. Timberframing and I go way back and I chose not to attempt that very joint a couple of years ago on a fence project.

I have an eight foot tall white cedar fence and needed to replace all posts. Glommed onto some cedar 6x6x14s and life was good til I reached the last post in the run. I'd failed to account for a drop in grade for which I should have used a 16 footer. Had a long scrap of 6x6 PT kicking around and used an 18" long half lap joint secured with carriage bolts and urethane glue. The joint is half below grade and half above. So far so good.