How to Level a Sinking Deck Post or Footing (Step-by-Step)

TL;DR: A sinking deck post almost always traces back to a footing that lost soil contact, usually from poor drainage, frost heave, or a footing poured too shallow (less than the local frost depth, often 12-42 inches depending on your state). Small settling of under 1 inch can often be fixed by jacking the beam, adding shims or a helical pier bracket, and re-tamping the base. Anything past 2 inches of tilt or a footing that's cracked usually means pulling the post and repouring.

_Last reviewed: July 2026 · 7 min read_

You noticed one corner of the deck bouncing or a board line that used to be flush now sits noticeably lower. That's not cosmetic. It means a footing underneath has moved, and left alone it will keep moving every freeze-thaw cycle until a post pulls loose from the beam.

Okoniq Property Hub logs the exact date and photo of every deck repair so you can track whether a footing is stabilizing or sinking further year over year.

Why do deck posts and footings sink in the first place?

Footings sink because the soil under them stopped supporting the load evenly. The three usual causes are a footing poured above the frost line, water pooling against the post base, or a footing that was never wide enough for the load in the first place.

Frost heave is the biggest culprit in northern states. If a footing sits at 18 inches but your local code requires 36 inches to get below the frost line, the ground under it freezes, expands, and pushes the concrete up and sideways every winter. Come spring thaw, it settles back down slightly off-level. Repeat that for a few seasons and the post visibly leans.

Water is the second cause, and it's the one most owners can actually fix. If drainage around the deck isn't routed away from the posts, soil under the footing turns to mud during heavy rain and loses its bearing capacity. A footing that looked solid in July can sink an inch after a wet October.

How do you tell if a post or footing has actually sunk?

Check with a 4-foot level against the post and measure the gap at the bottom of the beam where it meets the post. A gap over 1/4 inch means the post has dropped relative to the rest of the deck frame.

Walk the deck and look for a low spot where boards dip, then trace it back to the nearest post. Dig around the base of that post with a hand trowel, 4-6 inches down, and check whether the footing is cracked, tilted, or has visible daylight underneath one edge. A footing that has separated from the post base by more than 1 inch, or that rocks when you push on it, has lost its bearing entirely.

It's worth checking the joists at the same time, since a sinking post often puts extra stress on the connection above it. If the joists near that post show rot or soft spots, the settling problem has likely been going on longer than you think.

How do you level a sinking deck post or footing?

For minor settling under 1 inch, jack the beam, shim or add a helical bracket, and re-tamp. For anything worse, you're pulling the post and repouring the footing.

Minor settling (under 1 inch):

1. Place a hydraulic bottle jack (rated 6,000+ lbs) on a solid base near the post, under the beam it supports.
2. Jack slowly, no more than 1/8 inch at a time, checking level every few pumps. Never lift more than 1/4 inch in a single session — you can crack the beam or ledger connection.
3. Once level, slide in pressure-treated shims or a galvanized post base shim kit between the post and footing, and secure with structural screws, not just nails.
4. Backfill and tamp soil around the footing, sloping it away from the post so water doesn't pool there again.

Major sinking (over 1-2 inches, or a cracked footing):

1. Support the beam with temporary jacks on either side of the failed post so no load rests on it.
2. Remove the old post and break out or dig around the failed footing.
3. Dig to your local frost depth (check your county building department; this ranges from 12 inches in the Gulf South to 42+ inches in parts of the Midwest and Northeast).
4. Pour a new concrete footing, minimum 8-10 inches diameter for a standard deck post, using a tube form and a post-base bracket set while the concrete is still wet.
5. Let cure per bag instructions, typically 3-5 days for load-bearing strength, before removing temporary jacks.

| Repair Type | When to Use | Typical Cost (DIY materials) | Time | |---|---|---|---| | Jack & shim | Settling under 1 in, footing intact | $30-$80 | 2-3 hours | | Full footing repour | Settling over 1-2 in, cracked footing | $150-$400 per post | 1 weekend (plus cure time) |

When should you call a contractor instead of DIY?

Call a contractor if more than one post has sunk, if the deck is attached to the house and the ledger board has shifted, or if you're not confident jacking a structure safely. A deck with multiple failed footings is a structural problem, not a maintenance task.

Ledger board issues are the highest-risk part of any deck, since that's the connection point to your house. If you see gaps, rust streaks, or flashing pulling away where the ledger meets the house, stop and get a licensed contractor to inspect before you touch the posts. A jacking mistake near a compromised ledger can cause a partial collapse.

Also call a pro if the settling seems tied to a larger foundation or grading issue nearby. Decks built close to a house foundation can sink for the same reason foundations show water undermining problems — poor grading pushing water toward the structure. Fixing the deck post without fixing the grading just means you'll be back here in two years.

How do you keep a repaired footing from sinking again?

Regrade so water runs away from every post base, add gravel or a splash block under posts in wet areas, and recheck footings every spring. A five-minute level check each spring catches settling before it becomes a repour job, the same way a spring foundation check catches small cracks before they widen.

FAQ

How much does it cost to fix a sinking deck post?

A simple jack-and-shim repair runs $30-$80 in materials if you do it yourself, while a full footing repour typically costs $150-$400 per post in materials, or $500-$1,200 per post if you hire it out, depending on access and soil conditions.

Can I level a deck post without removing the deck boards?

Yes, in most cases. Jacking from underneath the beam doesn't require removing decking, though you may need to remove a skirt board or lattice panel to access the footing.

How deep should a deck footing be to prevent sinking?

It needs to sit below your local frost depth, which your county building department can confirm. That ranges from about 12 inches in parts of the Gulf Coast to 42 inches or more in cold northern climates.

Is a leaning deck post dangerous?

Yes, if the lean exceeds about 2 inches out of plumb or the footing has separated from the post, the deck can lose load capacity at that point and should be supported or repaired before regular use continues.

How often should I check my deck's footings?

Check every spring after the frost season and after any unusually heavy rain, using a level against each post to catch movement early.

This is educational information, not structural engineering advice. Call a licensed contractor or structural engineer if a footing has sunk more than 2 inches, if multiple posts are affected, or if you're unsure whether the deck is safe to use.