Dear Jerod,

This is an excellent question and one to which I have given some thought over the years.

Braces without pegs:-

I bet that these are all made from quite small section probably 3" x 4" and made from a good hardwood (typical Ohio barn - Rudy Christian please comment). These braces simply don't have a lot of room on the tenon to drill peg holes and still leave sufficient end relish on their tenons to make pegging a practical consideration. Thus brace number will be increased, probably to every available position along the length of a building. Braces of this size would not be appropriate on cross frames much over 8ft wide and also setting braces this size back into a housed mortise would further reduce the available tenon length and thus the reasons for non pegging become more apparent.

Bare faced tenons :-

Provided the brace stock material is of good straight and fairly thin section then an offset tenon is the quick and easy answer. If the brace stock material is twisted or of non uniform cross section then it is better to work from centre lines snapped on the timbers and hence a centrally mounted tenon might be more practical to layout and cut but the distance between the tenon and frame outside face needs to be kept about the same width as the tenon so fair facing of frame members will not necessarily be achieved and hence a move towards offset or centrally mounted braces is precipitated.

Centrally mounted tenons :-

Generally as previously advised this is the approach taken on big section material where offset tenons could allow for a gap opening up on the side of beam /post furthest from the tenon due to offset draw bore forces as the joint is pulled up.

Pilton barn has centrally mounted tenons cut into 10" wide cruck blades (see UK today).

Deep Section Braces :-

Braces which are 8" and deeper tend to be employed when two pegs are to be used per tenon. In England the braces on medieval buildings are often curved and are about 8 - 9" deep. This provides a even greater ammount of effective tenon width inside the mortice to help resist relish failure and help reduce joint/peg stress levels or even still resist pull out if a relish crack opens up in a tenon at a peg location. The peg diameter can also be reduced which in turn marginally improves the tenon performance against relish failures.

Rules of Thumb :-

Use bare faced tenons on material up to 4" thick in 1.25" / 1.25" (2.5" hardwood) or 1.5"/1.5" (3" hardwood) or 2"/2" (4" softwood). Beyond this thickness consider using offset or centrally mounted tenons in for example combinations of 1.25/1.25/1.5 (4.5" hardwood) or 1.5"/1.5"/3" (6" hardwood) or 2/2/2 (6" softwood) or 2/2/4 (8" softwood), etc.

I hope that your question will inspire many further thoughts and revelations.

Regards

Ken Hume