Crawl Space Adjustable Steel Columns: When to Use Them and What They Cost

Adjustable steel columns — also called Lally columns, jack posts, or adjustable steel pipe columns — are the professional’s choice for supporting beams in crawl spaces where moisture conditions make wood posts vulnerable to decay. Understanding when steel columns are appropriate versus wood, how installation differs, and what adjustment capability they offer allows homeowners to evaluate contractor proposals and understand why the recommendation makes sense for their specific situation.

Steel vs. Wood: Why Steel Is Preferred in Wet Crawl Spaces

Traditional crawl space support posts are 4×4 or 6×6 pressure-treated wood columns. Pressure-treated lumber is significantly more rot-resistant than untreated wood, but it is not rot-proof — it still deteriorates over 15–30 years in chronically wet conditions, and it remains vulnerable to termite damage (termites can penetrate pressure-treated wood, particularly in the South). The base of a wood post, where it contacts the concrete pier or soil, is the most vulnerable point — moisture wicks upward through the concrete, creating a persistently damp interface that accelerates deterioration.

Adjustable steel columns eliminate this vulnerability:

• Steel does not rot, does not support mold growth, and is not affected by soil moisture at the contact point
• Termites cannot penetrate or consume steel
• The base plate sits on the concrete pier surface with a thin profile that reduces moisture accumulation at the interface
• The threaded adjustment mechanism allows the column height to be changed after installation — a capability wood posts do not offer

Types of Adjustable Steel Columns

Screw Jack Posts (Adjustable)

The standard adjustable steel column for residential crawl spaces: a steel tube (typically 3″ or 4″ diameter) with a threaded screw mechanism at one or both ends that allows height adjustment over a range of 4″–12″ depending on the model. The top of the column has a beam seat or cap plate; the bottom has a base plate that sits on the concrete pier. Turning the adjustment screw raises or lowers the column top, allowing precise height adjustment and the ability to raise a settled beam or floor over time by periodic adjustment (typically no more than 1/8″–1/4″ per month to avoid structural stress).

• Standard residential range (most common): Adjusts 4″–6″, capacities of 20,000–40,000 lbs. Brands: Ram Jack, Terex, generic building supply brands. Cost: $80–$180 per column.
• Extended range: Adjusts 8″–12″ for applications where significant height variation or raising is needed. Cost: $120–$250 per column.

Fixed Lally Columns (Non-Adjustable)

Concrete-filled steel pipe columns (Lally columns) provide fixed-height steel support that is stronger than adjustable columns for equivalent diameter but cannot be adjusted after installation. Used primarily in new construction where heights are precisely determined during framing. Less appropriate for retrofit crawl space support where height adjustment capability is valuable.

Installation Process

• Footing verification: The concrete pier must be adequate to carry the column load. Inspect for cracking, settlement, or undersizing before installing a column. If the pier is inadequate, a new concrete footing must be poured (dig out the soil, form and pour a new footing, allow 7-day cure before loading).
• Column sizing: Calculate the load from the beam and floor above. For a typical single-family home with 40 psf live load and standard joist spans, a 3″ column with 20,000 lb capacity is adequate for most single-story midspan support applications. Consult the column manufacturer’s load table for the specific application.
• Column installation: Set the base plate on the pier (dry, no adhesive typically needed for permanent installation). Extend the column to make contact with the beam bottom face. Tighten the adjustment screw to achieve snug contact without lifting the beam — do not over-torque at installation.
• Raising a settled beam: If the purpose is to raise a settled beam or floor section, raise the column no more than 1/8″ per week — this allows the framing above to adjust gradually without creating stress cracking in drywall, stuck doors, or structural issues. Document the starting position and track adjustments over time.

Cost and ROI vs. Wood Post

• Adjustable steel column (3″, standard): $80–$180 for the column unit
• Wood post (4×4 PT, 4′): $15–$30 for the lumber
• Installation labor (per column, standard clearance crawl space): $100–$250 regardless of steel or wood
• Total installed per column — steel: $180–$430
• Total installed per column — wood: $115–$280
• Premium for steel over wood: $65–$150 per column

For a crawl space with 6 support columns, the premium for all-steel replacement over wood is $400–$900 — a small additional cost for a component that may last the life of the structure without replacement, versus a wood post that may need replacement in 15–25 years in a humid crawl space. For columns being replaced in a crawl space being encapsulated, the additional cost of steel is almost always worth the differential.

Frequently Asked Questions

When should I use adjustable steel columns vs. wood posts in a crawl space?

Use adjustable steel columns when: the crawl space has a history of moisture problems (even after encapsulation, steel is more durable); the existing wood post failed due to rot and the moisture source has been addressed; you want height adjustment capability for raising a settled floor; or the installation is in the Southeast or other high-termite-pressure region where wood posts are vulnerable to termite penetration over time.

How much can I raise a floor with adjustable steel columns?

Adjustable steel columns can raise a settled beam up to 6″–12″ depending on the model range. The critical constraint is not the column’s adjustment range but the rate of raising — no more than 1/8″–1/4″ per month to allow the framing, drywall, and finish materials above to adjust gradually. Attempting to raise a settled floor to its original position in a single adjustment will crack drywall, stick doors, and may cause structural stress at connections.

Do adjustable steel columns need a concrete footing?

Yes — the column’s base plate must rest on a concrete pier or footing adequate to distribute the load to the soil below. A column sitting on bare soil will settle over time. If no pier exists at the required location, a new concrete footing (8″–12″ deep, 12″–16″ diameter) must be poured and cured before the column is installed. The footing cost adds $200–$500 to the installation.