Lateral loads can be resolved in timber frame design by using wood bracing, normally in “compression only” joints, but sometimes the braces are engaged in both compression and tension by embedding steel tie rods in the brace.

Often, architects prefer to use short braces, or no braces at all. In those cases, the lateral loads must be resolved in the wall and roof systems like in a conventionally stick framed buildings. A positive fastening system needs to still be designed between the wall system and the timber frame. With good fastening between the walls and the posts, uplift from the lateral loads can be transferred through the posts bases into the foundation.

When window walls are part of the design, resolving the lateral loads gets trickier.  Glass necessitates designing for very small deflections to prevent the glass from cracking or the seals on multi-pane windows from cracking and clouding.  Large braces can be placed in front of the windows, usually with hidden or exposed steel tie rods, to resolved the lateral loads, or a steel moment frame can be built within the wall outside of the frame to resolve the loads. Perpendicular wind loads are also a concern when building window walls. Timber or steel columns can be installed to take care of deflection in the plane of the window wall.

Another way to resolve lateral loads is to use X-Braced diagonal tie rods between the timber columns. The x-bracing is a very contemporary look. some designers love it, and others prefer a more traditional solution.

When a clean timber look without braces is the goal, steel tee channels can be embedded between the timber column and the horizontal girt above to create a moment connection (see photo below).

Timber brace with hidden steel tie rod.

Timber Framed Window Wall

Timber and steel moment connection,

Steel Rod X-Bracing

Yes, one way to resolve lateral loads in a timber frame is to create a moment connection at the bottom of the timber columns. that can be done with a secure base plate bolted and epoxied down to concrete and a knife plate that extends up into the post.

Other post bases include timber-linx, stand-offs and simple rods, but they don’t resolve lateral loads on their own. They can resolve uplift from shear walls however.

Timber post moment base with knife plate.

Post base with rod & plate.

Post base with stand off and timber linx

Post base with rod and timber linx.

Yes, peg size does matter when designing a timber frame. This can be illustrated when thinking about the area of a circle, i.e. how the diameter of a peg relates to the peg’s cross sectional area and therefore its ability to resist bending and failing. PI*R Squared is the formula for area. The formula for a 3/4″ peg is 3.14*0.75/2*0.75/2= 0.44″sq . Whereas the formula for a 1″ peg is 3.14*1/2*1/2= 0.78″sq – almost double the size with just 1/4″ more in diameter. An 1 1/4″ peg has an area of 1.23″sq. , a 63% increase in area and therefor strength over a 1″ peg.

There is a caveat though; the larger the peg size, the more “relish” or distance behind the peg is required to achieve the full design load. the NDS (National design standard for wood construction) requires seven times the diameter of the peg for full value. I.e. 5.25 inches is required for a 3/4″ peg, 7″ is required for a 1″ peg and 8.75″ is required for a 1 1/4″ peg. That is a lot of relish and reductions can be taken. Joe Miller of Fire tower Engineering did quite a bit of research on this topic and  wrote an article in the Journal of Structural Engineering on peg design.