The Forestry Forum

General Forestry => Timber Framing/Log construction => Topic started by: PeterJackson on June 14, 2021, 03:56:43 PM

Title: Question about oak beams on a post joint
Post by: PeterJackson on June 14, 2021, 03:56:43 PM
Thanks for having me in the forum.  I've been lurking for a while and reading all I can.  Thanks also to the folk that take their time to respond and build this great community.

I'm building a simple backyard structure around a green oak frame which is approximately 4.2m x 2.7m using 150mm square timber.  It will have a flat roof from OSB.

I would like to have the beams meeting on the same plane on top of the posts.  I know there have been many threads about this and believe me when I say I have read them all.  But, it would still be wonderful if someone could offer some guidance.  I've settled on two possible designs and would greatly appreciate any feedback on them.  I hope you're OK with mm.  If not I can upload with inches.

The first is a pegged joint I've seen here before.   The tenons are 40x100x70.

(https://forestryforum.com/gallery/albums/userpics/66837/oak2.jpg?easyrotate_cache=1623700004)

The second is based on a half lap, but to keep more timber in the long beam, I have given it 2/3 instead of 1/2 of the depth.  The tenon is 30x80x60.

(https://forestryforum.com/gallery/albums/userpics/66837/oak.jpg?easyrotate_cache=1623700167)


In each case, I will add pegs through the tenons, and I will add braces on each corner - so 8 in all.

Which of the two do you think is better?

Thanks Peter
Title: Re: Question about oak beams on a post joint
Post by: PeterJackson on June 16, 2021, 11:44:30 AM
I seem to have started the least popular thread ever on this forum   :D
Title: Re: Question about oak beams on a post joint
Post by: doc henderson on June 16, 2021, 12:09:17 PM
sorry Peter, I am not a post and beam guy, but some are.  it appears you have failed to create any huge controversy.   :)  welcome!  from where do you hail?  I see mm.  what is your experience, and age group?  you may want to add to your profile.  
Title: Re: Question about oak beams on a post joint
Post by: PeterJackson on June 16, 2021, 01:26:42 PM
Thanks for your reply Doc Henderson - I have done as you suggested.  

I'm in my early 50s, living in Wiltshire UK, a computer programmer by profession, and enthusiastic to take on new projects.  I've done plenty of woodwork before but never an Oak frame.  The structure I'm building now is a precursor to a bigger project to build a workshop in the garden.   We had an Oak framed extension to the house a few years ago, and my current project is a simple garden shelter that will complement it nicely.

Title: Re: Question about oak beams on a post joint
Post by: doc henderson on June 16, 2021, 01:48:55 PM
@Brad_bb (https://forestryforum.com/board/index.php?action=profile;u=6191)   @Jim_Rogers (https://forestryforum.com/board/index.php?action=profile;u=95)  @Don P (https://forestryforum.com/board/index.php?action=profile;u=17) 
Title: Re: Question about oak beams on a post joint
Post by: Jim_Rogers on June 16, 2021, 07:30:53 PM
Your timbers need to sit on the post, but your exploded drawings don't show how much is sitting on the post.
I totally don't like the second one at all.

Jim Rogers
Title: Re: Question about oak beams on a post joint
Post by: PeterJackson on June 17, 2021, 06:48:21 AM
Hi Jim.  Thanks for looking.

I have 25mm of the short beam (closest to the viewer with the SketchUp logo) resting on the post.

The other beam does not rest fully on the post - just the 125mm that's left after removing the 25mm.

Hopefully the measurements are clearer in this image:

(https://forestryforum.com/gallery/albums/userpics/66837/oak2_28229.jpg?easyrotate_cache=1623926847)
Title: Re: Question about oak beams on a post joint
Post by: bannerd on June 17, 2021, 12:02:26 PM
Yeah, I don't like the second one at all either.  Maybe if the column was moved over out of the pocket.

The first one should work fine, shrinkage would be trivial.
Title: Re: Question about oak beams on a post joint
Post by: PeterJackson on June 17, 2021, 04:29:22 PM
Thanks bannerd.  I'm happy with the first version.  I'll start cutting at the weekend unless any else sees a problem with it.
Title: Re: Question about oak beams on a post joint
Post by: Brad_bb on June 18, 2021, 01:01:28 AM
Most timberframers try to avoid all those joints occurring at the same place.  Why do you want them doing this?  Often you drop the tie beam down below post to plate or post to rafter joint.  If you're putting a floor over the tie, you would install your floor joists on top of the tie and they could be in the same plane as your plate top or bottom if desired.  In your case, instead of a floor, it would be joist for your roof in the plane you want.  Why not do it traditionally to achieve what you want.  Maybe you want a "modern" look?
Title: Re: Question about oak beams on a post joint
Post by: PeterJackson on June 18, 2021, 08:47:19 AM
Hi Brad.  From reading other threads, I'm aware that framers try to avoid a 3-way joint like this.  At the same time, I've seen it on so many garden structures.  Yes - I think it looks more modern and that's the look I want to achieve.
Title: Re: Question about oak beams on a post joint
Post by: tadamson on June 29, 2021, 05:14:03 PM
I struggled with the same type of joint.  I received some great feedback from the forum and ended with this design.  Fabrication is in progress.  I've struggled with if I need to basically house the plates on the post to account for varying lumber thickness and to help hide what might not be a perfect joint.  As of right now, I'm opting for no housing.

My plan initially was to use the same type of joint you have in your first drawing, but I struggled with how to actually assemble it.  I'll likely be doing the assembly myself, so a lapped joint will make it easier for me.

Both plates will rest fully on the post at least 2".


(https://forestryforum.com/gallery/albums/userpics/66106/Joint7~0.jpg?easyrotate_cache=1625001132)
 
(https://forestryforum.com/gallery/albums/userpics/66106/Joint8.jpg?easyrotate_cache=1620825123)
Title: Re: Question about oak beams on a post joint
Post by: PeterJackson on July 10, 2021, 04:45:49 AM
Thanks tadamson.  I saw your discussion, and I've seen that joint on the timberframehq website.   I think it will work well with larger timbers but I'm only using (6").

I don't fully understand your joint though.  In the 1st picture, the red beam is resting fully on the post - as shown by the vertical line on the red beam that follows the post line.

But in the second picture, the full-size red beam looks like it is flush with the post - as shown by the post being on the same line as the cut-out in the red beam.