Footings and Foundations

Ironwood Home foundations are not much different than any other home. The home is built on typical slab on grade with grade beams, raised foundation with a crawl space and basements. One notable difference is the first floor shear panels are bolted directly to the foundation. 

No matter what type of foundation you choose there are many common details which can be reused from one home design to another. These details are written into the Base Plan Set. 

With the loads being transferred directly into the foundations the anchorage design and details stay the same. The anchors are designed for loads in a 3-story building, allowing for future vertical additions without touching the original construction. This may eliminate the need for tie-down straps around the structure, TBD through proper structural calculations. 

Slab on grade is the easiest to build. There may be some extra costs due to the requirement for a flat and level surface specifications which are more stringent than most slab foundation homes. 

The shear panels must be level and square with little tolerances to ensure the prefabricated structural frame and wall sections assemble properly. I do not recommend trying to shim the shear panels above the slab to level them out. Since all gravity, wind and seismic loads are carried by these panels we want them to be securely fastened to the foundation.

The exterior framing is set back 1-1/2" from the edge of the slab or foundation wall. This is to accommodate 1/2" plywood sheeting and 1-1/2" continuous insulation  and then the siding which hangs below the top edge of the foundation. There is a 1/2" tolerance built into this dimension for slight forming errors and form bending during concrete pour. 

Raised floor and basement foundations require a different detail. The floor trusses must be installed between the foundation walls, not on top of them. Consideration into the height of the stem wall is critical. 

The mud sill plate is set and leveled on top of the foundation wall and recessed 1-1/2" back from the edge, same as in a slab foundation. Pressure treated rim boards are anchored to the foundation walls on 2 sides of  each frame, these support the floor trusses at the first floor level. This assembly is covered with 1-1/8" T&G plywood before setting and anchoring the shear panels. This assembly maintains the best, most direct path of the structural loads to the foundation. 

Every shear panel requires a foundation underneath it. This will create some extra foundation and basement walls in places where traditional homes don't. This affect is more pronounced when placing structural frames off-set from each other. The added foundation sections also makes the home much stronger than traditional homes, increasing their wind and seismic capabilities considerably.