Water Shedding Mortises

Got a new trick for whomever is interested.

Been dealing with frames that can receive driving rain onto knee braces. From there water travels down kneebrace and gets into post mortise.

With a 4" tenon that usually bears level in the post I have created a slope. Essentially a 3/12 pitch. 4" over level 1" up plump.

The neat part that is that the Makita mortiser's angle on the third canted setting is this exact angle. You can layout a line 1" up from bottom of mortise for guidance and plunge with Makita. 4.5mm on the ruler aligned with the bottom of mortise should get you to the right place. I plunge the rest of the mortise with Mafell.

Creates a nice plumb to slanted mortise for water extrusion, in theory that is.

Cheers.

I like it Mo! I have in the past taken a V-Tool to carve a swale like divirter under such circumstance, and will add this bit of thinking to mortises which could see wind driven rain in the future.

Doing restoration with regularity, such causal roots of rot are always high in my mind. I see posts lost to pinhole leaks directed into brace mortises with some frequency, this incubation often exacerbated by shredded materials introduced by mice when setting up nests in that empty square part of a brace mortise above the tenon.

As an aside, when sucked into the whole slope vrs no-slope debate, I have pointed out this potential and how I have seen leaks in brace mortises without such sponge-like nests (often scribe era sloped ones without room for such - Yes they do exist) fare far better - And have suggested that I always put slopes in barns (every Barn hosts mice) for this reason.

This sounds similar to the way I've done porch braces / struts before, in hopes of helping the water get out of the post:





Is this what you are describing?

Will, that is good food for thought (pun intended)! Have not thought about the triangular void before. Where do you use your v gouge? I was also thinking of the same tool to create a diversion trench on the upper side of the brace before entering the post. Like a V that sheds to each side.

Mike, yes exactly like that! No chiseling required as the makita mortiser chain cuts on entering and leaves a nice true facet where it matters!

Funny that not 2 weeks ago I was pondering the same dilemma while making a pair or lamp posts with braces. I considered the sloped brace mortice but took the lazy way out and caulked around the brace.I even thought of drilling a 1/4" diagonal drainage hole.
How did the Makita behave when plunged at an angle? Was kickback an issue?

Ray. I have thought about the drainage hole too.

Mortiser was fine. I would recommend plunging the rest of the mortise first. That third canted setting works just fine. You are using the tool as intended. Works great!

Edit: now that I think about it, not exactly as intended. But with a decent clamping effect, no issues with kickback this far. I did take my time with the cut.

Mice can get into the oddest places. I am adjusting a room in my basement, the washing machine was plugged into an outlet with no face plate, I was removing the whole thing and noticed a string hanging out of the box, it was a dried mouse tail the rest of the mouse was inside the box, I wonder if it got fried?

I don't use a chain morticer, but this could also be done with a bored hole by shimming the machine and using bevel square. Also use a durable wood like black locust when posting out in the open.

Mo, I tend to do the divirter on the back of braces low enough to catch and divert most of the water which might hit it, but high enough that any flow runs down high enough that capillary action will see it spread and then evaporate and not just be drawn into the mortise - 6" or so.

I've done the V and just a diagonal slash towards the shoulder side, thinking that likely to introduce less water into the depth of the mortise.

In considering weep holes it seems they would soon fill with sluff, dust and insect leavings, and water were it somehow directed towards them, would simply fail to flow and be held in that sponge.

In this area of Indiana, sloped brace mortises are the common rule (though you do find a few square mortises) When this is the case, in all such barns I have surveyed I do not often see the brace mortises as a location of post failure.

Usually, post failure in our barns occurs at the foundation -especially when the old boulder foundations were 'upgraded' to concrete footers, and the concrete causes the bottoms of the posts to fail. It is also fairly common to find posts failing where a through mortise holds 2 heavy girts. But post failure isn't the issue I see most of the time, usually I see roof failure and plate failure, resulting in a structure becoming unstable and the forces becoming unbalanced, causing the structure to tilt and collapse (and leading most people to incorrectly identify the problem as a foundation issue)

David -

I wasn't intimating that Brace Mortise wettings were the most common form of Post failure, just that it is not all that uncommon.

Often when it is an issue, the outside faces appear sound and the only telltales are water-stains and fungus in the area of the Brace to Post connections.