Mortise and tenon

= Mortise and tenon is a building technique that allows frame building to be done without any nails or screws. Instead two boards are joined by fitting one inside of another and holding them together with a wooden peg.

The sections below provide examples of mortise and tenon construction at Rancho Mastatal.

The table below shows a demonstration piece created to display the mortise and tenon concept that applies the square rule. The square rule is a method that allows one to work with timber that has two square sides (sides that are flat and at a 90 degree angle with each other).

Image	Description
	This is an image of two blocks fitted together using the mortise and tenon technique.
	This is how the blocks look apart.
	This is the tenon piece. The tenon is inserted into the mortise. The part that fits into the mortise has a smaller width than the rest of the timber, because of the square rule (described above table). Only two sides of the timber are square, but the four sides of the tenon are made square by slightly reducing its size. A flat notch is made in the mortise piece (shown below) that is just big enough to fit the tenon piece.
	This is the mortise piece. The tenon fits snugly inside the mortise.
	The mortise and tenon should be prepared so that they will share square sides. The square sides of the timber should be positioned to face the outside or insulation side of the structure if conventional insulation material is used. This is because insulation material adheres better to a flat surface.
	A hole is drilled into the tenon that will be slightly above the holes drilled into the mortise by about 1/8". Holes are also drilled into the mortise. The holes should be about 1/8" below the tenon hole. This 1/8" offset is to ensure that when the peg is hammered into the holes the mortise and tenon pieces are pulled together by the peg. If they were offset in the opposite direction than the weight of the structure would rest on the peg rather than the frames, which would make it a very fragile joining.

The table in the image to the right was made using the mortise and tenon technique and took more than 200 labor hours to build. It is a very stable and grounded table that is expected to last for a long time. The gallery below displays a few images of the joinings used to make the table.

The list below links to other structures at Rancho Mastatal that use the mortise and tenon technique.

• Rancho Mastatal Starboard Cork house
• Rancho Mastatal composting toilets
• Rancho Mastatal showers