Monday, September 1, 2014

Lock Notches, Why and How

I have to say that log cabin building is not as straight forward as most would think. Get some logs cut some notches and pile them up. How hard could it be? Everyone did it 150 years ago and just with hand tools. No chain saws.

Well if you have been following the construction of cabin #3 you know there is more to it than meets the eye. Lock Notches are just that. Take a look at the picture below of the first one in this cabin.
Can you see it? Well lets take a look at the why and how of Lock Notches...

With the log sitting on the rough notch and the final notch scribed in orange you can see that if cut this deep (over 1/2 of log diameter) it would weaken the log at the notch. The solution is to cut a  Lock Notch. This will be a block of wood left in the notch. The orange horizontal line going through the middle of the notch shows the size of the block to be left in the notch. About 3 inches in this case.

With the log rolled over the notch is cut to the depth of the block to be left in the notch.

After being cleaned out the width of the block to be left is laid out. The material on either side of the block (marked by X's) can now be chiseled out as per final scribe.

Next the receiving notch for the block is laid out in the lower log.

Both halves of the lock notch cut and ready.

Walla! Now do you see the lock notch?


  1. Never knew the detail. I have done some timber framing but never a log cabin. It is fascinating to witness the process, not sure how much fun it is to build.
    Michael in Maine

  2. Very clear pictorial, thanks for posting! However, isn't the main purpose of the lock notch to make the joint resist movement in both the X and Y directions? I can see how cutting the full notch would weaken the log though, so that's a good reason too.