Why floors sag in the first place
Three reasons, in order of frequency in our service area:
- Undersized joists for the span — common in pre-1980 homes built before modern span tables. A 2x8 spanning 16 feet was once considered fine; today's code requires 2x10s.
- Moisture damage — joists sit in damp crawl spaces for decades, lose strength, deflect. Encapsulation stops the moisture but doesn't restore the lost capacity.
- Pest damage — termites or carpenter ants weaken specific joists. The home doesn't fall but a single joist can lose 60% of its strength.
A bouncy floor is the leading indicator. The actual structural failure follows years (sometimes decades) later — but the bounce is the warning.
What the jack-post system does
An adjustable steel jack post supports the joist mid-span, transferring the load to a concrete pier on grade. Done correctly:
- Spacing per ICC IRC R301 — typically 4'–6' on center along the worst-deflected joist runs
- Steel post sized to capacity — 4" Schedule 40 is the standard; heavier where loads warrant
- Pier base — 18"×18"×8" poured concrete pier minimum, on undisturbed soil, sized to local frost depth
- Joist hat — galvanized steel cap with proper bearing surface, hand-shimmed to existing joist
- Adjustable — the post itself has a threaded adjuster; final tightening done over 30-day settle period
What to avoid: screw-jack posts on dirt with no concrete pier. These work for 6–18 months, then settle. We've heard of "fixes" that lasted less than a year. Concrete pier is non-negotiable.
The 30-day settle period
The home doesn't fully settle onto the new posts immediately. The crew installs the system, tightens each post to the calculated load, and you live with the home for 30 days. The crew returns, re-checks each post with a torque gauge, and makes final adjustments. This is included in the network specialists' standard scope and not optional.
What you'll spend in 2026
- Single-room repair, 3–4 posts, existing piers — $1,800–$2,800
- Half-house repair, 6–8 posts, mix of existing and new piers — $3,800–$5,400
- Whole-house repair, 10–14 posts, all new piers — $5,800–$7,400
- Pre-1980 home with also-needed joist sistering — add $1,800–$3,400
Permits
Whether stabilization requires a permit varies by jurisdiction. Davis and Yolo County require permits for any structural alteration including jack-post systems. Sacramento County usually does not require permits for jack-post-only work when no new framing is added. Network specialists confirm at the inspection.
Common questions
Can I just put a 2x4 column on a piece of plywood?
You can. It won't last. The plywood deteriorates, the 2x4 rots, the load shifts, and the floor sags again — usually within 2–4 years. There's a reason real jack-post systems use steel + concrete.
Will the floor visibly straighten after installation?
If the sag is recent and slight, often yes — over the 30-day settle period. If the sag has been there for 20+ years, the floor framing has set in that shape and won't fully reverse. The fix prevents further sag but doesn't always erase existing deflection.
Do I also need encapsulation?
If moisture is the underlying cause of the joist damage, yes — otherwise the fix is treating the symptom. The diagnostic on the homepage walks through this; the network specialist confirms at the on-site inspection.