When reusing barn beams in a new structure, what should I do about old mortices? I was thinking about making snug fitting wood plugs to glue in place as the original tennon would have, then cross drill it and drive peg through, and finsh the plug and peg flush to the beam. I do understand that old mortices should be oriented in areas of the beam that will see lower stress where possible. Do people do this when reusing barn beams or do they do something else?

Plugging up the hole is a good start but adding a peg is probably unneccessary. Also by doing so you basically cut through the wood fibers and therefore you actually weaken the beam further.
I would recommend turning the mortises up so that they end up under compression when the beam is loaded.
If there are mortises on both sides you might have to support the beam at say midspan.

I believe that piece of wood is called a "Dutchman".

Dave

Ah yes. That is what I was thinking- plug on compression side of beam. I would not be drilling a new hole, but reusing the existing hole from the original peg that wehn through the mortice. The new peg would fill the hole to give it more strength as well as cosmetically making it not stand out so much. Thank guys.

brad,

I don't think you will be able to regain much strength by filling holes. Especially in a beam. If more strength is needed, your best bet is to get another bigger or sounder piece of wood. An engineer is a good person to have on your team if there is any doubt (and there usually is or at least should be).

Now, if you don't like the looks of the empty holes, then plug away. I personally would rather look at legacy joinery than contemporary dutchmen.

gook luck with your project,

Gabel

What is legacy joinery? trying to use existing mortices? It may be possible every now and then, but the new structure will be a very different design.

I plan to compensate for the morticed areas of the beam by upsizing the beam size to compensate. I had the plugging in mind for looks and maybe to get a small percentage of the strength back (in compression).

And I am an engineer (ME). I'll be refreshing myself in truss/statics loading analysis and stress analysis. I'll also definitely have my worked checked by another professional with this type of experience. The more cross checks the better. Being able to do much of the calculations myself will allow me to experiment with designs and get close with the minimum sizing of members.

I've plugged old beams on several projects and I like to use old tenon tips. I'll trim them off salvaged beams and save them for this use. As far as strength goes , don't rely on an old beams for support structurally ! They should be used as a decorative feature and be required to carry there own load only. Most old timbers are stronger than new sawn ones , but mortices and notches can obviously weaken the timber. When in doupt over build. There are also several methods for re-iforcing a spanning timber from above(if head room allows) to eliminate posts.

brad,

Legacy joinery is joinery from a previous life, and I didn't mean to imply that you can reuse the joinery in a new structure -- there are way too many variables to allow that to happen often. I will repeat that I think trying to regain strength by plugging old mortises is a losing proposition.

As for aesthetics, I have done it both ways -- filling the holes with carefully chosen color/grain/hewing pattern-matched dutchmen, as well as leaving the old mortises open. It's all up to the client.

Being a framer with a history problem, I like to be able to see the hand tool marks inside the old joinery myself. I can see how they did things and what tools they used, and it seems that I often see things I've never noticed before.

Tell us a little more about what your planning to build-- sounds like it will be fun.

gh

Being somewhat foreign to most of your terminologies used, I do have to ask: Why are the plugs called dutchmen?

When I do plug or "dutchman" I like to think I'm adding my own history to the pieces and it will drive someone else nuts trying to figure why that darn thing was plugged. We sometimes leave a message or coin or what not inside too. Every timber project is a mystery for someone in the future to puzzle over. Yeah why are they called dutchmen ! Gotta go my typing finger is cramping up.