Crawlspace Support helps with Sagging floors, cracked drywall, and doors that rub and it usually starts in the crawlspace. The fix is simple in concept: carry the load to the ground with the right beam, the right jack posts, and real concrete footings. This guide gives you clear symptoms to watch for, how we size and install supports, realistic costs, and what to expect on site. For full structural planning and coordination with permits and inspections, see our page on structural carpentry.
Signs you need crawlspace support
- Floors dip toward the room center or a hallway line
- Tile or grout cracks repeat after repairs
- Baseboards gap at corners or counters pull from walls
- Posts sit on bare dirt or thin patio pavers
- Wood shows dark staining or softness near exterior walls
What a correct Crawlspace Support system includes
- Beam sized for span and load, LVL or steel by design
- Jack posts or lally columns spaced to reduce joist spans to code
- Concrete footings sized to soil and load, not just a slab block
- Moisture control so the fix lasts: drainage, vapor barrier, and ventilation or dehumidification
Jack posts vs permanent columns
| Option | Best use | Pros | Watch out for |
|---|---|---|---|
| Adjustable jack posts | Fine tuning during lift and seasonal tweaks | Easy to set, allows staged lifting | Needs a real footing and locking after final set |
| Filled lally columns | Permanent support after elevations are set | No seasonal creep, clean look | Height must be exact, no quick re-adjustment |
Bottom line: Use adjustable posts for lift and tune, then lock them or swap to permanent columns once levels are set.
Footings are non negotiable for
A post on dirt will sink. A post on slab can punch through. Correct footings spread the load.
- Excavate to undisturbed soil
- Form and reinforce per span and load
- Pour concrete pads that match engineered size
- Use base plates and post caps with through bolts or structural screws
How we lift without cracking your house
- Survey and layout with laser elevations and reference marks
- Temporary shoring where needed for safety
- Footings placed and cured to strength
- Beam set under the low joist line
- Jack posts added and adjusted in small lifts over several days
- Lock off at final elevations and verify doors, trim, and counters
Small lifts reduce stress on finishes. Expect minor drywall touch ups. Large one day lifts cause cracks and callbacks.
Moisture, rot, and termites
Structural fixes fail in wet crawlspaces. We address the cause or the problem returns.
- Replace any rotten sill plates and rim joists with treated stock
- Add drainage, gutters, or grading to keep water out
- Install a vapor barrier on the soil and seal seams
- Dehumidify damp crawlspaces to protect wood and steel hardware
- Treat any active termites before new work goes in
Typical scopes and cost drivers
| Scope | What is included | What moves the price |
|---|---|---|
| Add 1 beam with 2 posts | Footings, beam, jack posts, hardware | Span length, access, finish patching above |
| Multiple post line under hallway | Footings every 6 to 8 feet, beam, posts | Number of footings, crawlspace height |
| Sill and rim repair addon | Removal, treated replacements, flashing | Extent of rot, utilities at edge |
| Moisture control package | Vapor barrier, vents or dehumidifier | Crawlspace size, power availability |
| Engineer design and permit | Calcs, details, permit fees | Jurisdiction turnaround, complexity |
Spend on footings, beam sizing, and moisture control. Do not waste money on posts set on blocks or thin pavers.
FAQs
Can I just add more posts on my slab
No. Posts need real footings. A slab is not a footing.
How far apart should posts be
Depends on beam size, joist span, and load. Expect 6 to 8 feet on center for many residential beams, but we size it to conditions.
Will lifting crack my finishes
Minor cracks are common. Staged lifts and good planning keep repairs small.
Do I need an engineer
For longer spans, multi story loads, unusual framing, or by jurisdiction rule, yes. We coordinate when required.
Can I DIY jack posts
You can buy posts at a store. The risk is poor footings, over jacking, and missed load paths. Hire a pro if you want predictable results.
Process that keeps projects moving
- Assessment and elevations
- Engineer details where required
- Permit submission
- Footings and beam install
- Staged lift and lock off
- Final inspection and moisture plan check
If you want floors that feel solid and stay level, we will size the beam correctly, set posts on real footings, control moisture, and pass inspection the first time. Start with an assessment here: structural carpentry.