Disadvantages of Using Wood Posts in a Crawl Space
Crawlspace foundations are very popular, and it’s easy to see why. Builders often prefer this type of foundation because it requires much less excavation work than a full-height basement foundation. Crawlspaces can be built quickly and cheaply, offering a very handy way to “get out of the ground,” in builder lingo.
Unfortunately, placing too much emphasis on economy can lead to some poor construction practices. Some contractors deliberately take shortcuts and cost-cutting measures, while others do it because they don’t know any better. Either way, using the wrong materials and details inevitably causes problems.
Wooden poles: easy and cheap
A typical crawl space foundation contains at least one joist or girder that runs the length of the foundation and provides mid-span support for the first story joists. Since the “footprint” or plan of the house is often too wide for a single joist to span its full width, one or more centrally located joists support the ends of the joists that typically overlap each other and the joist. .
Joists or rafters also require mid-span support to prevent sagging near the middle. Wooden poles were once used to provide this support while resting on concrete platforms or pillars.
This framing system has been a standard treatment used in conjunction with basement foundations for many years. The joist or rafter can be made from a single piece of lumber of large dimensions, such as 6×10 or 6×12; but the framing crew likely built a thick, deep beam by nailing together several 2×10 or 2×12 beams. Regardless of the treatment of the beam, wooden studs were installed at regular intervals under the beam to prevent buckling. For framing contractors, this all-wood structural system is simple, inexpensive, and easy to execute.
Problems with wooden posts
The weak link in the floor framing system described above is undoubtedly the wooden posts that are supposed to keep the joists straight and strong. They often fail in this regard for various reasons.
To get started, carpenters often wedge thin wooden wedges (or tapered wood shingles) between the top of the wooden post and the bottom edge of the beam to better fit the post into place. Usually, because the post was cut a bit, the beam lost some of its width due to shrinkage or natural irregularities common to dimensional lumber.
While shims may do their job initially, they are also prone to shrinking, shifting, and compression from the weight of the flooring. Over time, the joist can also shrink as it loses moisture, creating a loose stud. When the support under the joist is inadequate, the joist and the floor begin to sag.
Another problem that compromises the stability of the flooring system is mold and rot that often accumulate in a humid basement environment. A wooden post can easily absorb moisture from a concrete base that is in contact with moist soil. Since mold thrives where there is cellulose and moisture, wooden studs can become weak due to decay associated with mold. When this happens, your strength and stability suffer.
The Solution: All-Steel Adjustable Brackets
Anyone who has to deal with sagging, bowing or bouncing floors knows that this situation is not something you want to endure for long. Home security and property values suffer, and like fault studs under the first floor, furniture must be shimmed to maintain its proper orientation.
Fortunately, the problems caused by wooden support posts in a tight space can be overcome by replacing these posts with adjustable steel support posts designed precisely for this retrofit application so that they can be lifted slightly if the joist shrinks. You never have to worry about a steel post becoming weak from rot, and some posts are treated with a thick galvanized coating to prevent corrosion problems.
Remember: wood is good in many construction applications. But for studs that support the center of the main floor over a crawl space, adjustable steel studs provide long-term stability, strength and durability that wood studs can’t match.