Preserved Wood

Preserved wood foundations, also called permanent wood foundations are constructed with pressure treated wood framing and pressure treated plywood cladding. The cavity between the framing members is insulated and drywall is generally applied to inside surface. The floor can be constructed of preserved wood or concrete. This is the same pressure treating process that is used for decking and fences.

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PWF have been gaining popularity over the last 50 years.
Some of the benefits claimed for Preserved Wood Foundations include:

  • Easy to build.
  • Easy to modify to add more rooms or change the shape in the future
  • Structurally strong
  • Long lasting
  • Easy to finish
  • Resistant to insect and rodent damage
  • Ideal for the Do-it-Yourselfer
  • However like all other foundation types, PWFs are not maintenance free and problems can arise from time to time.

Permanent Wood Foundations (PWF)

1. Water Penetration/Waterproofing

The DELTA-MS waterproofing membrane system provides two lines of defense. The first is an impermeable plastic sheet that is waterproof. The second is the dimpled structure that offers a free drainage path. In the event that water passes the first line of defense, it can flow freely down the air gap to the footer drain. Unlike a coating, DELTA-MS bridges all size cracks, ignores damage points and deflects water as well as soil dampness. It also allows for the drainage of construction moisture to the footer drain.

2. Weeping Tile

All Building Codes require a perimeter drain system regardless of the type of foundation. Root obstructions may be able to be removed using a sewer machine but this also is a temporary fix. Trees need water and the weeping tile around your house is an excellent source. There are really two options, replace the weeping tile or abandon the weeping tile. We call the process of replacing the perimeter drain tile an Exterior Excavation which as its name implies, is done from the outside. Abandoning the tile does not mean ignoring it and letting it leak, or filling in the basement with concrete.

Preserve Wood History

The early 1960's saw much research into the use of preserved wood for foundations was researched heavily, but it was not until the mid 1970's that the concept gained acceptance. In the 40 or so years since then, hundreds of thousands of houses have been built on preserved wood foundations.

3. Window Wells

Any time a window, air vent, or chimney etc., are located below grade a well of some sort is required. A window well is a shaped piece of corrugated galvanized steel, built on-site wood or concrete or a custom prefab designer well. A basic galvanized well may seem like a simple item with simple installation. If that were true, fixing window wells would not feature so prominently in Ltd.'s business. Improper sizing, placement, installation, drain structure are some of the problems remedied on a regular basis by Visit our Window Well page for more information.

4. Snap Ties or Rod Holes

When a poured foundation is constructed, rods or ties are used to hold the forms together and provide proper spacing when the concrete is poured between them. While there are many actual types of tie rods, they fall into two categories, permanent and removable. Removable rods leave a hole through the foundation which is often plugged with cork and hydraulic cement. Permanent ties are snapped of after the forms are removed and a remnant piece of steel is left inside the wall. In the early days of pouring concrete they would often use a small block of wood and twisted wire. The problem with wood is obvious, it rots, metal can rust, and holes can just leak. With newer styles of permanent ties that are snapped off (called snap ties), contractors will hit the tie with a hammer to snap them off, If this done too early, the tie will become loose in the concrete and when the tar that is applied to the outside fails, the tie will leak. If there is sufficient quantity or access is limited, an Exterior Excavation may be recommended. In some cases, we can inject the tie or rod hole with epoxy or urethane. Your Estimator will show the best solution for your home.