One of my clients asked me about wood foundations a few months ago and I thought it might be a good idea to compile some information on the 4 main types of foundations found and the benefits and drawbacks of each.
Concrete foundations are the most common type of foundation. When pouring an integral foundation, aluminum, wood or insulated wall forms are placed on the footings, clamped together, and supported to maintain their shape while the concrete is poured. Once the forms are set, rebar is placed vertically inside the wall channel to support and add additional strength to the concrete wall once the molds are removed. Temporary forms are usually taken down after one week, at which time the concrete is cured enough to support itself. The concrete will continue to cure and emit moisture for much longer. When using insulated concrete forms, they remain in place and insulate the home.
- Concrete foundations are the strongest and most durable form of foundation
- Fire Resistant – Concrete foundations are very fire resistant so the houses structure would be well protected in the event of a fire
- Virtually maintenance free
- Repel insects
- Leaks – Concrete tends to crack and lead to leaks. If there is a severe leak you will have to dig up the earth around the foundation all the way to its base
- Most expensive foundation to initially construct and takes the longest
Block Wall Foundation
Block foundations use cinder blocks ( typically 8 x 8 x 16 inches) that are stacked on each other and cemented in place with mortar. The process starts on the top of the footings with each row forming its own course. The blocks are then reinforced with rebar placed vertically in the holes or cells and filled with concrete.
- Concrete block foundations are very fire resistant so the houses structure would be well protected in the event of a fire
- Low cost for material
- Easy to find
- Relatively easy to install
- Virtually maintenance free
- Repel insects
- Concrete block is highly resistant to cracking and crumbling in extreme temperatures, unlike poured concrete.
- A well-built, concrete block home is virtually soundproof, as long as doors and windows are well insulated. They also insulate against cold and heat, and help a home use less energy to maintain comfortable temperatures.
- If you live in an area with a high water table, then using concrete blocks for your basement can lead to seepage and water damage. This will need to be countered with quality waterproofing material and paint.
- Can only hold 1/5 of the weight of a poured concrete foundation
- Susceptible to lateral forces and buckling
PWF (Permanent Wood Foundations) are not new and have been around since the late 1960’s.
They are an in-ground, engineered construction system designed to turn a home's foundation into usable living space. It is an alternative to conventional block or poured concrete foundations in many situations. They are constructed like lumber-framed walls in the rest of the home, with plywood sheathing attached on the exterior. They use pressure-treated wood, a renewable resource, with a preservative to protect the wood against decay, fungi and termites.
- Cheaper construction costs
- Easy replacement of posts or beams
- Possibility of reusing the wood if the house is torn down
- Wood basements can feel warmer. Concrete absorbs a lot of radiant heat from your skin, and can make a basement feel cold, even if the air temperature is warm. Wood absorbs much less radiant energy.
- Not as resistant to water damage and likely to eventually rot after several years of being exposed to moisture
- Not as strong as concrete but strong enough to adequately support the weight of a home
- Water proofing a wood basement can be expensive and time consuming, negating the benefits over a concrete foundation
- Require more maintenance in the long run
- The boards can warp over time under the weight of the home
- Wood is also susceptible to insects and rodents
Stone foundations were the standard fare in houses built before World War 1. Most stone foundations have, or had at some time, a mortar coating on their interior. The purpose of this coating was to help hold the stones in place. This mortar coating will inevitably flake off from moisture migration, revealing the surface of the stones. As this coating continues to erode, the soft, sandy mortar in between the stones begins to fall out. When this occurs, re-pointing is needed as soon as possible to refill the voids where the old mortar fell out.
- Some home owners find the stone visually appealing
- Doesn’t rot like wood
- Requires a lot of maintenance
- Prone to water infiltration
- Decades of water infiltration will cause degradation to the stone foundation walls. The result can be bulged walls from unnecessary static pressure or settlement of the foundation, deteriorated mortar joints from excessive moisture or loose stones and missing mortar joints from aging and movement.