Concrete Block Foundation With a Crawl for a Home

A well-crafted concrete block foundation is critical to supporting a house structure. The block foundation helps ensure the house will not shift or sag over time, so it's important to follow all required building codes. From a practical perspective, a block foundation provides needed crawl space for accessing heating system ductwork, plumbing lines and electrical wiring under the house. Building the crawl space deep enough, such as 4 of 5 feet, makes accessing any part of it much easier.

Copy of local building codes
Building permit
Percolation test printout
Stakes
String
Trencher
Concrete
Metal rebar
Concrete blocks
Mortar
Carpenter's level
Plumb bob
Concrete lintel
Header beam
3/4-inch plywood
Heavy-duty hinges
1-by-8-inch boards, 8 feet long
Flat capping blocks

Instructions

- 1
  Obtain a copy of local building codes and get a building permit. Hire a professional company to perform a soil percolation test before starting the foundation. Conduct the test to check the absorption rate of soil surrounding your home. Do this "perc test" to ensure the soil will allow proper drainage for the home's septic system, if there will be one. Take documentation of percolation test results to get the building permit finalized.
- 2
  Talk with a consultant to check for any excavation problems before digging foundation footing to hold the blocks. Look for issues regarding large rocks, loose soil, or natural gas lines or utilities underground.
- 3
  Stake off the perimeter of the crawl space digging area, using string to define the outline of the foundation dimensions. Rent a trencher to scoop out a crawl space at least 4 feet deep. Keep in mind that a shorter crawl space can create major issues for workers who need to access plumbing and wiring or need to perform pest control.
- 4
  Construct the footings to support the blocks forming the foundation wall. Create the space for the concrete pour by digging a small trench to hold concrete that is approximately 15 inches wide by 6 inches deep. Install metal rebar to reinforce the concrete in the footing.
- 5
  Lay concrete blocks with mortar approximately 8 rows high. Build the concrete walls to form the foundation wall by using string stretched between foundation corners to keep the rows level. Construct corners first, making sure they align when checked with a carpenter's level. Check them with a plumb bob as well to ensure they are exactly vertical. Fill the core of the blocks with concrete as you work to help strengthen the wall.
- 6
  Leave space in the blocks for a crawl space door accessible from the lawn area. Install a concrete lintel or a header beam across the top of the door opening. Build a crawl space door from 3/4-inch plywood attached to wooden framework around the door opening with heavy-duty hinges.
- 7
  Allow mortar to dry thoroughly before installing metal flashing and a board capping to cover the blocks around the entire perimeter. Install boards 8 inches wide by 1 inch thick by 8 feet long with concrete nails, or use flat capping blocks held in place by mortar around the wall perimeter. Build the floor joists on top of the capping.

How to Add on a Foundation to a House

Difference Between Scissor Doors & Butterfly Doors

Home Additions