Monolithic Concrete Foundations

Deciding which method to use when building a foundation for a home is critically important. Most basic homes utilize a monolithic slab foundation. This is the fastest and least expensive way to “come out of the ground”. The decision to use this method is usually based on cost, speed and profitability of the builder. Excavation is made for the entire home footprint and the edges of the footprint are framed with dimensional lumber using wood and steel stakes to hold the forms in place. In colder climates rigid insulation is attached to the form lumber to create an insulated slab.

The depth of the footing component of the monolithic slab is determined by the geographic location and based on the frost line for the area. The depth is mandated by local building codes. 2 to 3 feet is relatively standard. Rebar is along the bottom of the footer and across the slab field in a grid pattern. rebar is also placed vertically from the base of the footer and bent at a right angle to transition to the field area and lends strength to the transition from footer to slab. All the rebar is tied in place with wire to remain in place until encased  in the poured concrete.

Walls are attached to the monolithic slab by means of J bolts set in the wet concrete. The J bolts will protrude through the base of the wall which is usually a pressure treated (to resist damage from water) 2 X 6 and be fastened down by washers and a nut. The interval is usually every 16 inches and the bolts line up between the vertical studs for easy access and installation. A key monolithic consideration is the ability to shim the vertical wall to achieve a plum wall if the monolithic slab is not accurately level. Failure to shim the walls to achieve Plumb will translate to problems all the way to the roof and cause great difficulty where walls meet and ceiling achieve level. Building cement block or insulated concrete form wall (ICF) on a slab that is not level required additional labor and methods to avoid walls that lack plumb and distorted corners, windows and door openings.