Thread: Help with butt joints for 100x100 posts

Use housing joints.

Originally Posted by China

Use housing joints.

Well, I've learnt a new term. A little research, and behold, what I thought was a trench, and later found out was also called a dado, is also a housing joint!

The Americans call them Dado's because. well, they are Americans, the trench is the female part of the joint the entire joint is called a Housing joint.

I did a little more research and according to Wikipedia, they are called a Dado in the US and Canada, Housing in the UK and a Trench in Europe. (I guess it's a joint not used anywhere else in the world!)

Originally Posted by EB42

Dear experts,

Relative beginner question here. I am building a “chunky” outdoor sofa, mostly using 100x100mm (i.e. 4”x4”) cypress pine posts.

Because of the length, I need supporting posts in the middle as well as on both sides. This means that I need to be able to butt joint horizontal posts on both sides (left and right) of a vertical post.

I assume that pocket screws won’t be strong enough for such heavy pieces. I am thinking of blind dowels, but fluted dowels only seem to come in 10mm diameter, which seems way too small for a 4x4 cross-section. I assume that making my own dowels out of bigger round moulding won’t work as it won’t be fluted so it will be too hard to bang in, plus I couldn’t use a doweling jig so accuracy is likely to be an issue.

I don’t have the skills or tools to achieve mortise & tenon joints in this size timber, especially as the tenons would have to “miss each other in the middle”.

What do you suggest? Can I get away with just dowels & glue, and maybe a few pocket screws for good measure?

Use a half-lap joint. Glued, these are very strong and relatively easy to cut ....





Regards from Perth

Derek

Thanks for the suggestions re half-lap and housing joints. However I’m unsure how this could work given that I need to make TWO butt joints to the same piece.

To make it clearer, I need to end up with a T shape: a vertical piece, with two horizontal pieces butt-jointed right to the top of it, one on the left-hand-side and one on the right-hand-side.

It seems to me that both the half-lap and housing joints would end up removing all the “meat” from the vertical piece since I need to make cutouts for both horizontal pieces joining at the same point.

Also, there is the aesthetic issue: the wife wants the vertical pieces to look “complete” all the way to the top, i.e. not to have visible chunks cut out of them!

lag screws on an angle

is this the type of "joint" you're trying to build?

joint.jpg




if so maybe look at some sort of castle joint... can also try "half lapping" the two horizontal pieces and just drive a few screws (plus glue) through both of them into the vertical piece

joint2.jpg

Originally Posted by EB42

Thanks for the suggestions re half-lap and housing joints. However I’m unsure how this could work given that I need to make TWO butt joints to the same piece.

To make it clearer, I need to end up with a T shape: a vertical piece, with two horizontal pieces butt-jointed right to the top of it, one on the left-hand-side and one on the right-hand-side.

It seems to me that both the half-lap and housing joints would end up removing all the “meat” from the vertical piece since I need to make cutouts for both horizontal pieces joining at the same point.

Also, there is the aesthetic issue: the wife wants the vertical pieces to look “complete” all the way to the top, i.e. not to have visible chunks cut out of them!

I hope this does not come across as rude; it is meant to be objective - give up on this project. You are insufficiently experienced for it. It is too complex for you.

There is a minimum standard of joinery needed if you want the sofa to last longer that two minutes. You cannot keep dumbing down the joinery. Find another design, or buy it.

Regards from Perth

Derek

Good on you Derek for saying what most of us were thinking, just to add EB42 find yourself a book or books on furniture construction, and start with some less complicated.

Hmm, really not what I was expecting to hear. Just because I haven’t dealt with a particular issue before makes me unworthy to even try something new?

I always believed that people improve their skills in something by trying something a bit more challenging than what they did last time. As an example, I built a perfectly good garden bench that has survived fine for several decades of use, it just used thinner timber and so the joinery was simpler.

I thought that a forum like this would give encouragement to less experienced people to push themselves to the next level, rather than telling them to give up because they asked a dumb question. Anyway, I’m sure your intent is good, so thanks, my mistake, apologies for wasting your time.

I don't think you wasted any ones time, but there comes a point when advice over a forum becomes inadequate.
Advice was was forth coming and you di not seem to comprehend.
Therefore advice to seek advice is appropriate.

Originally Posted by EB42

Hmm, really not what I was expecting to hear. Just because I haven’t dealt with a particular issue before makes me unworthy to even try something new?

I always believed that people improve their skills in something by trying something a bit more challenging than what they did last time. As an example, I built a perfectly good garden bench that has survived fine for several decades of use, it just used thinner timber and so the joinery was simpler.

I thought that a forum like this would give encouragement to less experienced people to push themselves to the next level, rather than telling them to give up because they asked a dumb question. Anyway, I’m sure your intent is good, so thanks, my mistake, apologies for wasting your time.

It did not give me any pleasure to make those comments. However, you stated at the start that mortice-and-tenon joinery (which is the mainstay of tables and chairs) was beyond your expertise, then then proceeded to reject increasingly simpler, alternative joinery. It gets to a point where the joinery is inadequate for the task.

If you wish to grow as a woodworker, you need to be prepared to take on more complex joinery … not find more complex designs and dumb them down.

Perhaps you need to post a photo of the sofa you are wanting to build, and we can comment more directly.

Regards from Perth

Derek

Originally Posted by EB42

Hmm, really not what I was expecting to hear. Just because I haven’t dealt with a particular issue before makes me unworthy to even try something new?

I always believed that people improve their skills in something by trying something a bit more challenging than what they did last time. As an example, I built a perfectly good garden bench that has survived fine for several decades of use, it just used thinner timber and so the joinery was simpler.

So you posed a question to the experts you received a reply you then proceed to tell the expert it won’t work, you are then told by the expert to build something else, you say that’s not what you want to hear.

You also say that you have used thinner timber previously so the joinery was simpler, however joinery is joinery 50mm, 100mm or 600mm
a picture or drawing is always a good idea when posing a question as we cannot see ‘your’ idea.

you say dowels and pocket screws then why not make a jig out of ply or masonite and use 4 or 5 dowels on each join.

without a picture or sketch of your sofa we can to and fro all day - you state because of the length you need a central support - in my mind a 100mm post would traverse horizontally a very long way without support - so you can see what we picture from what you type can and most always will be different.

you assume glue and screw won’t be strong enough, yet you don’t give any information as to the sofa if it is going to move every day or stay put, glue and screws can be strong enough you just need the right size and quantity with an appropriate glue, for what you can see you are trying to achieve.

In relation to joinery use woodworking books (or Pinterest, web searches) to find images of what you are building so you can zoom in and see what joins are used. Type woodworking joints and “how to” into Pinterest and that is a good start.

Cheers

Originally Posted by derekcohen

Perhaps you need to post a photo of the sofa you are wanting to build, and we can comment more directly.

Thanks Derek for the positive reply - I'll take up your invitation and try one more time with more information, as I do think there have been some misunderstandings along the way.

1. What am I trying to build?
   Something similar to the attached photo (sorry a bit blurry & need to zoom in, snapshot taken from a video).
   However aiming to make it shorter - approx. 3200mm length, 750mm depth, 550mm height.
   Planning to use 100x100 cypress post stock, rather than the even more chunky sleepers used in the photo.
   It will probably remain fixed in one spot (too heavy to move).
2. What is the T-shaped joint I'm talking about?
   See basic sketch below. I've drawn this with dowels, just as an example.
   To give an idea of weight, the horizontal pieces would be ~1450mm length, obviously supported on both sides.
   Note how the horizontal pieces attach on the side of the vertical piece, rather than sitting on top of it (aesthetic preference, I realise this makes it harder, but the wife is always right).
3. How was I thinking of doing these?
   My original question was really to test whether dowels would be sufficiently strong.
   I assume that 10mm commercially-available dowels would be far too small, so I was thinking about cutting them out of bigger dowel mouldings (e.g. 25mm?), making them long enough to go half-way into each piece (i.e. 100mm long), and using several per joint.
   However I'm still not sure whether this would be strong enough, and I'm concerned that large unfluted dowels may be impossible to properly insert (lack of air escape, lack of glue flow).
   Any advice on this would be appreciated.
4. What's wrong with half-lap or housing joints?
   It's not that I am unable or unwilling to do them. It's that I'm not sure how they can work when two pieces are being joined in the same spot - i.e. I would end up removing all the "meat" from the vertical piece.
   As someone has suggested, I could of course do this and glue/screw the resulting pieces into what remains of the vertical piece. I can do this as a fallback, but as per comment above, I'm trying to avoid cutting into the vertical piece for aesthetic reasons (i.e. I'd like it to have a proper "top" if possible).
   If I'm missing something here, please let me know - I'm happy to try something new.
5. What's wrong with mortise & tenon?
   I'm happy to learn & give it a go.
   However I don't think I could cut mortises all the way through (e.g. router won't plunge that far), so I don't think I can replicate the pegged M&T look in the photo.
   I could use blind mortises that only go say 4-5cm into the stock, if the advice is that this should be strong enough.
6. What do I have?
   Circular saw, plunge router
7. What don't I have?
   Table saw, router table, drill press
   Experience cutting a good mortise & tenon (but happy to learn)

I hope this helps, thanks in advance.

Photo of similar design.JPGT joint sketch.jpg