# Mortising fence posts?



## NickB (Sep 24, 2013)

I'm going to build a small wood fence in our front yard. Something simple. I'm thinking a basic 3 rail like this:









What I don't want is something shoddy looking with boards nailed to the front of the posts like this:









So, I'm looking for advice on how to fasten the rails to the posts. I've considered just toe-nailing or even pocket hole screwing them, but I feel like they'll open up and look like crap. My thoughts are to mortise the posts to allow the rails to "float", but I'm not sure how well that will go. Mostly because it's challenging to level a post in a hole vs just setting it in and cutting it off at the right height later, but I guess it can be done.

I'm thinking about boring out most of the waste with a forstner bit, then using a chisel to square them up. Not sure if it makes sense to do this on the drill press or just on the ground with a corded drill. Or maybe something else all together?

Any thoughts?


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## shoot summ (Feb 21, 2014)

Not that hard to set the posts, set the first one, and the last in a line, then run a string between them on the top. All of the posts in between will have the top touch the string. Much like installing pickets on a fence. You need gravel in the bottom of the hole to keep moisture from the end of the post anyway, use the gravel to level the posts.

Depending on the number of posts, that will be a lot of mortises.

A couple of random thoughts...

Split the posts, dado out the mortise area, then glue/fasten them back together. Some sort of decorative metal 'strap" around them to hold them together.

This place has TONS of neat metal work supplies...

https://www.kingmetals.com/

Or some sort of half lap where the rails aren't necessarily mortised, but would look better than just running them as stringers.

ETA; looks like you can buy vinyl posts like your first pic, not sure if it fits your design/style, but it looks like they are pre-routed...


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## Brian T. (Dec 19, 2012)

Just outside my village, BKB Manufacturing is a mill producing split western red cedar products.
The fence posts are about 5" x 5" x 64". Laid on their sides, the mortices are drilled two at a time with the post moving a little such that each mortice is a compact row of 3 holes. The rail pieces have their edges near the ends rounded off but I didn't see how that was done.

You might need to ream out the mortice holes a little, the fences are more decorative than functional but look nice once weathered a silver gray. Up and down the district, I've found some stretches of very old fence which look to have been morticed with a drill of some sort.

I try to catch a few posts for wood carving before they get to the morticing machine. Also, I buy 24" WRC shake blocks from them.


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## NickB (Sep 24, 2013)

shoot summ said:


> Not that hard to set the posts, set the first one, and the last in a line, then run a string between them on the top. All of the posts in between will have the top touch the string. Much like installing pickets on a fence.
> 
> Depending on the number of posts, that will be a lot of mortises.
> 
> ...


Should have mentioned this is a low-budget project going on the Home Depot card, so it will be done in all PT pine. As much as I like the look of metal straps, I don't think I can justify the expense right now.

The half lap idea, though that may make more sense. Thinking a quick-made sled and a dado stack could make short work of those and look pretty good, too.


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## shoot summ (Feb 21, 2014)

NickDIY said:


> Should have mentioned this is a low-budget project going on the Home Depot card, so it will be done in all PT pine. As much as I like the look of metal straps, I don't think I can justify the expense right now.
> 
> The half lap idea, though that may make more sense. Thinking a quick-made sled and a dado stack could make short work of those and look pretty good, too.


Just realize there will be(a lot) of shrinkage, I would cut them tight, will probably have at least 1/8" gap when they dry out.


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## mmwood_1 (Oct 24, 2007)

I would disagree with the method of running a string from the first to the last one, if you actually want them level. You will not get a level reading with a string because it sags. The longer the string, the more sag. Use a rigid level. As long as you can read a level accurately, you can do pretty well.

As for splitting the posts, using a dado, then rejoining the posts, well, I wouldn't do it that way. I don't care for the method of splitting the support post apart. Personal preference, I guess.

Mortising is not a difficult thing to do. I think what I would do is to make a ply template which has a stop at the top end for the post, with the 3 mortise patterns on it. Drill out the bulk of your waste, then clamp the template on the post, run a long router bit and using a guide bushing, trim the mortises. Flip it over and do it from the other side. Your mortises will be neat and clean, all consistent distances from the top of the posts.


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## shoot summ (Feb 21, 2014)

mmwood_1 said:


> I would disagree with the method of running a string from the first to the last one, if you actually want them level. You will not get a level reading with a string because it sags. The longer the string, the more sag. Use a rigid level. As long as you can read a level accurately, you can do pretty well.
> 
> As for splitting the posts, using a dado, then rejoining the posts, well, I wouldn't do it that way. I don't care for the method of splitting the support post apart. Personal preference, I guess.
> 
> Mortising is not a difficult thing to do. I think what I would do is to make a ply template which has a stop at the top end for the post, with the 3 mortise patterns on it. Drill out the bulk of your waste, then clamp the template on the post, run a long router bit and using a guide bushing, trim the mortises. Flip it over and do it from the other side. Your mortises will be neat and clean, all consistent distances from the top of the posts.


I disagree, you pull it tight, and there is no sag. If there was an issue with sag then the 1000's of construction folks that use string for a reference are building sagging items everywhere. Just for grins I shot a laser on 150' of fence I installed. No sag on the posts, or pickets over 150'. The string method is way easier and faster when you are trying to plumb a post, as well as set it to a certain height. Guess we all have to find the method we like best.

I didn't think it was a great idea either, as I said, it was just random thoughts. The OP already indicated he didn't like it either.


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## Belg (Oct 2, 2011)

shoot summ said:


> I disagree, you pull it tight, and there is no sag. If there was an issue with sag then the 1000's of construction folks that use string for a reference are building sagging items everywhere. Just for grins I shot a laser on 150' of fence I installed. No sag on the posts, or pickets over 150'. The string method is way easier and faster when you are trying to plumb a post, as well as set it to a certain height. Guess we all have to find the method we like best.
> 
> I didn't think it was a great idea either, as I said, it was just random thoughts. The OP already indicated he didn't like it either.


I have used the string method for installing things level b4 on a level plane, and just wonder how do you handle this situation when your installing fencing on a rolling hillside or a slope? I'm thinking there are different techniques for that??


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## woodnthings (Jan 24, 2009)

*A built up" mortise ....*

Instead of hogging, drilling, routing away large amounts of material, consider a built up mortise. Imagine a 1 X 4 on it's flat. On top are sections of 2 x 4 located and spaced apart to form the mortises for your rails. On top of that in another 1 X 4 which make the lamination complete. I did something similar on this Mission Style headboard for the cross rails:

 



A weatherproof glue and some screws will hold it all together. A few passes in the planer or over the jointer and the glue line will be invisible.

The principle is the same here:
http://www.woodworkingtalk.com/f2/workbench-integral-legs-22946/


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## FrankC (Aug 24, 2012)

With the fence shown in the photo the post are set, then the rails are fed through the posts, how would a mortice and tenon style rail be installed?


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## NickB (Sep 24, 2013)

shoot summ said:


> I disagree, you pull it tight, and there is no sag.


My experience is like yours. I've used strings many times for jobs like this and never had a problem. If I were looking for truly level, I've used clear vinyl tubing to make a water level and that works quite well. 



woodnthings said:


> Instead of hogging, drilling, routing away large amounts of material, consider a built up mortise. Imagine a 1 X 4 on it's flat. On top are sections of 2 x 4 located and spaced apart to form the mortises for your rails. On top of that in another 1 X 4 which make the lamination complete.
> A weatherproof glue and some screws will hold it all together. A few passes in the planer or over the jointer and the glue line will be invisible.


Pressure treated wood is always so wet. I don't think I'd be brave enough try this method in this application. Especially since they're going to be in the ground. It's a clever method, though, so thanks for the input.



FrankC said:


> With the fence shown in the photo the post are set, then the rails are fed through the posts, how would a mortice and tenon style rail be installed?


That's a good question, FrankC. I guess I convinced myself that they'd go in one-by-one with the rails being installed as you go. Another option may be to make them through like you mentioned. 

At this point, I am leaning towards the lap joint idea, but I'm concerned with stability. PT wood is just so unstable to begin with and hogging that amount of waste on one side seems like it would cause the posts to buckle as they dry. 

I believe that the dadoes will cause the post to want to warp inwards towards the cut side (anybody know?). If that's the case, but the dadoes are filled by the rails, will this be enough to keep them reasonably straight? I mean, it's just fence, but still, I don't want a noticeable warp... Any thoughts?


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## shoot summ (Feb 21, 2014)

NickDIY said:


> My experience is like yours. I've used strings many times for jobs like this and never had a problem. If I were looking for truly level, I've used clear vinyl tubing to make a water level and that works quite well.
> 
> 
> Pressure treated wood is always so wet. I don't think I'd be brave enough try this method in this application. Especially since they're going to be in the ground. It's a clever method, though, so thanks for the input.
> ...


I really don't think it will cause any issues, you could alternate sides to create an interesting pattern.

I forgot to mention another option, although since this is a budget install it probably won't work.

I wrapped 2" steel posts with cedar to look like 6x6's. Would be pretty easy to incorporate the mortise into the wrap, much like woodsnthings mentioned.


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## NickB (Sep 24, 2013)

This project is finally DONE!

Here's the thread.

Thanks again, shoot summ. I went with your dado idea.


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## Brian T. (Dec 19, 2012)

What a beautiful result!
If you had cared only for a rustic split western red cedar post and rail fence, come and visit.
BKB Cedar has the most violent and ferocious mortice cutter machine that I have ever seen.
I did not know that such tools could be bought!

Stuff a rail into the tenon machine, what happens in there, I don't need to know.


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## NickB (Sep 24, 2013)

Thanks, Robson Valley. I've done a couple mortises with a plunge router jig and I can only imagine that in the form you're describing. Something I'd like to see, actually!


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