Construction Business & Technology Conference

Building Mass at Hold-Downs

Before we leave the technical side of hold-downs and move into the practical points and pitfalls I want to mention the often overlooked resolution of hold-down force and building mass. The tension force generated by a hold-down must be transferred to:

A member capable of transferring the force on to other members;
A reinforced foundation capable of distributing the force beyond the hold-down location; or
A mass of footing whose weight (gravity force) exceeds that of the tension force.

Foundation at a Building Corner

I have identified the shear wall location by shading the 4x posts at each end.
Note that the majority of roof load bears on the perpendicular wall, not on the
shear wall. Thus the resisting moment of the wall is low...and the potential
hold-down force is high. In the absence of the ability to pick up adjacent
structure loads, the footing is deepened to create dead weight for the hold-down
to engage.

Foundation at an Exterior Wall

In a condition similar to the above, deadmen - masses of concrete below the typical
house foundation - are created to create mass directly under the hold-downs.
Because they are below grade, they can generally project out from the face of the
typical perimeter footing without causing a problem. Threaded rods, embedded in
the deadmen, function to tie everything together.

Foundation at a Building Corner

I have identified the shear wall location by shading the 4x posts at each end. Note that the majority of roof load bears on the perpendicular wall, not on the shear wall. Thus the resisting moment of the wall is low...and the potential hold-down force is high. In the absence of the ability to pick up adjacent structure loads, the footing is deepened to create dead weight for the hold-down to engage.

Foundation at an Exterior Wall

In a condition similar to the above, deadmen - masses of concrete below the typical house foundation - are created to create mass directly under the hold-downs. Because they are below grade, they can generally project out from the face of the typical perimeter footing without causing a problem. Threaded rods, embedded in the deadmen, function to tie everything together.