How To Build A Slab Foundation
Prior to construction, preliminary work is generally done. This preliminary work includes obtaining and presenting a set of building plans to the local building department for approval. The plans usually cover the structural, electrical, plumbing, mechanical systems and fire safety.
There may be other areas of the building construction that need plans and approval. Generally, the preliminary work is performed by the general contractor. Some localities may allow the prospective homeowner to act as the general contractor.
According to the building plans, the site is prepared for construction. This involves roughing out the driveway for access to the building, clearing brush, trees and removing unwanted obstacles.
A surveyor is enlisted to locate the exact corners of the building and batter boards are setup to stake out the corners. The batter boards are checked for squareness using a mathematical formula called triangulation. The foundation can be marked with a line of paint.
Now that the corners are marked, excavation may begin. Foundations must be dug to the correct depth according to the plans. A backhoe is generally used to dig a foundation. They tend to disturb the soil less than a bulldozier. If the foundation is dug too deep, do not back fill it with soil. The foundation footings must rest on undisturbed soil. Generally, the footing depth is checked by the local building department inspectors.
Before concrete is poured into the footing, rebar may be set to reinforce the foundation. This helps the foundation resist soil movement.
Fill With Concrete
The footings are back filled with poured concrete. The concrete is allowed to harden for a few days.
The plumbing lines are also set according to the plans prior to backfilling with soil.
The grade, for drainage, is checked to make sure that the minimum slope is ¼ inch per foot. Once all the lines are set and stubbed, the foundation work may continue.
After the footings have hardened, the foundation walls and brick veneer can be erected.
Achor bolts or straps are set in wet concrete to tie the sill plate to the foundation.
After the mortar in the foundation walls have hardened, the area is prepared for concrete backfilling. Before backfilling, however, the area is filled with gravel and 6 mil plastic is used to cover the gravel fill. The plastic will act as a vapor barrier.
The concrete is then poured and smoothed flush with the foundation walls.
Once the masonry work has been setup, the slab is poured and smoothed.
After a few days, the concrete hardens enough that the frame can be erected.
Before the framing begins, framing materials should be delivered to the job site. The most popular material for framing in the US is yellow pine. Our Lumber Guide will provide more information on lumber types.
Most house construction sites today employ truss framing systems. Truss systems are often used in floor framing and roof framing.
Once the framing materials are on site, the framing can begin.
There are various types of framing systems used for residential construction. For most houses in the US, frames are built one story at a time. The sill plate used for framing is generally pressure treated yellow pine that resists decay. In fact, any material that comes in contact with the ground or any masonry work must be highly resistant to decay.
Notice the size of the garage header. The longer the span the larger the head must be.
Exterior load bearing wall must have a double header plate.