Stretcher to Post Joinery
Posted: Sat Jan 23, 2016 2:24 pm
A request was made to talk about the joinery options and detailing for connections between post and stretcher. As I started drawing, I reflected that this is a slightly involved topic, and not something I think can be explained all that well in brief. That said, I don't feel like spending the rest of the day on this either, so instead, I'll chip away at it and people can throw in comments or heckles as they see fit.
I think the following drawing outlines the main conditions where we have to devise joinery between stretcher and post. The post section is 'a', the stretcher section is rectangular, measuring 0.33a x a:
I have centered the stretcher on the post face in each case.
At the bottom, we have the stretcher terminate at the post, though it can also pass completely through the posts and continue to some extent. The main thing is that it does not connect to further structural members beyond the post. It could also connect to the top or bottom post end.
In the middle we have a stretcher which meets the post and passes though, connecting to other structural members beyond in each direction. The stretcher itself can be one-piece as it passes through the post, or it can be two-piece, each of which joins to the other inside of the post. One could also have the end of the stretcher splice continue beyond the bounds of the post if desired.
On the top of the drawing we have a stretcher meeting the top of a post. Once again, the stretcher can be one-piece or two-piece. The post may connect to another member above the stretcher. This is the weaker form of connection mechanically as it bears on a minimum of 3 surfaces in the joint, one of which is end grain, while the stretcher passing through the post somewhere must meet at least 4 faces in the joint, two of which are end grain surfaces. Essentially this is a bridle joint, an open mortise and tenon. Not the strongest, and reliant upon glue for integrity, but there are some better ways to deal with this connection.
All these joints are strongest if the stretcher is one piece instead of two piece.
Stretchers may also meet one another at a post at a right angle, and again, the respective stretchers might terminate at the post, might pass through the post to some further point of connection, and may be one-piece or two-piece:
Now, it should be acknowledged that the above examples are dealing only with orthogonal relationships between the parts. The members could also meet at varying angles in relation to one another. Some joinery options will work for such cases, others won't.
So, there is a considerable range of possibilities to look at. And the above is only considering situations where the stretcher is 1/3 as wide as the post. All the same connections can be considered for stretchers that are 2/3 as wide as the post, 1:1, or even where the horizontal members are larger sections than the post. So, I'm going to stick to the 1/3 case for now.
I think the following drawing outlines the main conditions where we have to devise joinery between stretcher and post. The post section is 'a', the stretcher section is rectangular, measuring 0.33a x a:
I have centered the stretcher on the post face in each case.
At the bottom, we have the stretcher terminate at the post, though it can also pass completely through the posts and continue to some extent. The main thing is that it does not connect to further structural members beyond the post. It could also connect to the top or bottom post end.
In the middle we have a stretcher which meets the post and passes though, connecting to other structural members beyond in each direction. The stretcher itself can be one-piece as it passes through the post, or it can be two-piece, each of which joins to the other inside of the post. One could also have the end of the stretcher splice continue beyond the bounds of the post if desired.
On the top of the drawing we have a stretcher meeting the top of a post. Once again, the stretcher can be one-piece or two-piece. The post may connect to another member above the stretcher. This is the weaker form of connection mechanically as it bears on a minimum of 3 surfaces in the joint, one of which is end grain, while the stretcher passing through the post somewhere must meet at least 4 faces in the joint, two of which are end grain surfaces. Essentially this is a bridle joint, an open mortise and tenon. Not the strongest, and reliant upon glue for integrity, but there are some better ways to deal with this connection.
All these joints are strongest if the stretcher is one piece instead of two piece.
Stretchers may also meet one another at a post at a right angle, and again, the respective stretchers might terminate at the post, might pass through the post to some further point of connection, and may be one-piece or two-piece:
Now, it should be acknowledged that the above examples are dealing only with orthogonal relationships between the parts. The members could also meet at varying angles in relation to one another. Some joinery options will work for such cases, others won't.
So, there is a considerable range of possibilities to look at. And the above is only considering situations where the stretcher is 1/3 as wide as the post. All the same connections can be considered for stretchers that are 2/3 as wide as the post, 1:1, or even where the horizontal members are larger sections than the post. So, I'm going to stick to the 1/3 case for now.