Structural Repair · Service

Post and beam repair — the vertical path under the girder

Floors sag for more reasons than a tired beam. Posts crush, shift off pads, rot at the base or stand on soil that never deserved a house load. Fixing the wrong member is how people pay twice.

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In short

What is post and beam repair?

Post and beam repair addresses the vertical supports and the horizontal members they carry in basements, crawl spaces and some framed openings. A beam spreads floor load; posts take that load to footings or pads and into the ground. Many “sagging beam” calls are post-base rot, undersized columns or failed pads. Competent repair identifies which member failed before anyone cuts lumber, and it treats posts, pads and beams as one load path rather than three separate products.

Triggers

Signs you need post and beam repair

A post that no longer sits fully on its pad or has visibly crushed at the base
Soft or insect-damaged wood at the bottom of a crawl-space post
A steel lally column with rust, lean or missing plates
Floor sag that centres over a post line more than along a mid-span beam
A previous jacking job that used temporary posts still left as “permanent”
Water, poor drainage or soil movement under pad footings in the crawl space
Doors that stick in a pattern that tracks a post line more than a single joist bay
A home inspection flagged “temporary posts” or “inadequate posts” under the main beam

Seeing something not on this list? Browse structural repair problems by symptom →

The job

How post and beam repair actually works

Read the load path before buying a beam

Who carries what: joists to beam, beam to posts, posts to footings. A flashlight survey finds crushing, lean, missing connectors and water patterns. Jumping to a full girder replacement without this walk is how budgets explode and sound beams get cut for no structural reason.

Watch for: A quote that replaces the beam by default because beams sound serious. Demand a post-and-pad assessment in the same visit.
Engineering when the house is telling a larger story

Multiple failed posts, moving foundations or unclear alterations need an engineer’s design, not only a carpenter’s judgment. Permits follow the jurisdiction and the scope, and drawings protect you when the next buyer’s inspector opens the crawl.

Watch for: Major permanent changes with no drawings on a house that has already been altered badly once. Stop the DIY lally forest.
Temporary shoring that reaches competent support

Before removing or jacking, temporary posts must land on something that can carry load — not soft soil or a single brick. This is the same safety core as beam replacement, applied to the verticals, and it is non-negotiable on occupied houses.

Watch for: Bottle jacks on stacked lumber with no plan for what happens if something slips. Shoring is a system.
Post repair or replacement details

Rotten wood posts are replaced with treated or specified material, correct size, solid bearing top and bottom, and connectors that match the design. Steel columns need proper plates and plumb installation. Height adjustment is controlled — not a heroic weekend crank that cracks finishes upstairs.

Watch for: Sistering a rotten base with a scrap block and calling it permanent. Decay will continue above the patch if moisture remains.
Pads, footings and the ground

A perfect post on a failed pad still settles. Undersized blocks, soil washout and frost movement are foundation-adjacent problems. Some jobs become pier or footing work rather than simple post swaps, and that is a different price class than “new 4x4.”

Watch for: New posts on the same undersized patio block that sank last time. Change the bearing, not only the stick.
Beam work only when the beam actually failed

If the girder is checked, undersized or bearing poorly at ends, it may need repair or replacement — covered in depth on the beam replacement page. Coordinate so posts and beam are one designed system rather than two unrelated invoices.

Watch for: Replacing a beam while leaving crushed posts that will fail the new member next. Systems thinking is the hire.
Inspection, access restoration and moisture control

Permits may require inspection before finishes hide the work. Fix the water that rotted the post bases or you will meet the crew again. Leave the crawl safer and drier than you found it — vapour, grading and leaks are part of structural durability.

Watch for: Structural repair with no interest in the leak or grade problem that caused the rot. The next post will fail the same way.

Money

What does post and beam repair cost?

Post repairs can be modest when a single column and pad are the issue; costs rise with engineered designs, multiple posts, footing work and any beam replacement done in the same mobilisation. Crawl-space access and water remediation often influence labour more than lumber price.

See the full post and beam repair cost guide — by material, size and region →

Straight answer

When post and beam repair is the wrong call

Everyone else ranking for this is paid when you say yes. Here's when you shouldn't.

The only problem is a cosmetic sag from truss lift or non-structural finishes. Not every uneven floor is a post failure — diagnose first.
You planned to jack the house level in a day with rental jacks alone. Uncontrolled jacking cracks finishes and can overload members.
Foundation walls are failing and posts are a distraction. Get foundation assessment rather than decorating the crawl with new columns.
Moisture will remain and you only want wood replaced. Rot returns; budget drainage and vapour control with the structural work.
A beam-only failure is already confirmed and posts are sound. Use the beam replacement scope rather than this page’s post focus.
You need an engineer and the contractor refuses any design step on a complex failure. Find a different team.

Your options

Types of post and beam repair

Beam replacement

When the girder itself is the failed member.

Sistering joists

Joist-level repairs beside post lines.

Sagging floor

Symptom-led diagnosis path.

Structural inspection

When you need eyes before demolition.

Engineering referral

Design when failures are complex or multi-post.

Compare structural repair options side by side →

Before you sign

What to check when hiring for post and beam repair

Which members failed — post, pad, beam bearing, or beam span — and how do you know?

Forces a diagnosis instead of a default product.
What temporary shoring plan will you use, and what does it land on?

Safety and competence show up here first.
Is an engineer required for this scope in our jurisdiction?

Ambiguity becomes your liability later.
What post material, size and connectors are specified?

Vague “we’ll put a new post” is not a design.
How will you address moisture or soil issues under the pads?

Otherwise you are buying a sequel.
What inspections and what finished floor level should we expect?

Jacking can crack tile and plaster — plan for it.
Will temporary posts be removed and permanent connections documented in photos?

Future inspectors and buyers need a record of what is load-bearing forever.
Will you photograph concealed connections before leaving the crawl?

Future inspectors and buyers need evidence of permanent work, not tribal memory.

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Local pros

Post and Beam Repair near you

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Related work

Often done at the same time

Beam Replacement

Girder-focused work

Sagging Floor

Symptom diagnosis

Floor Joist Repair

Joist-level damage

Engineering Referral

When design is required

All structural repair services →

FAQ

Post and Beam Repair — questions people ask

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Is post and beam repair the same as beam replacement?

They overlap and are often done together, but the focus differs. This page emphasises vertical supports and pads; beam replacement emphasises the girder and spanning member. A good contractor assesses both before cutting either, because replacing only one side of a failed system is how callbacks start.

Can I replace a crawl-space post myself?

Temporary posts and uncontrolled jacking injure people and houses. Permanent structural posts need correct size, bearing and often permits. Hire for anything that carries floor load while you work under the house — the cost of a mistake is the floor system, not the post.

Why is my steel column rusty at the bottom?

Water and humidity at the crawl or basement floor. Address the water source and verify the column still has section left; heavy rust can mean replacement, not paint alone. A cosmetic spray over a thinned section is not a structural repair.

Will fixing posts level my floor completely?

Sometimes mostly; sometimes finishes have already taken a set and full cosmetic level would damage more than it helps. Structural safety and reasonable improvement are the goals — ask what level of recovery is realistic before anyone promises a billiard-table floor.

Do I need new footings?

When pads are undersized, washed out or never adequate for the load. Soil and water history matter. An engineer or experienced structural contractor should decide — not a default upsell on every post, and not a permanent “temporary” jack left for the next owner to discover.

How is this different from foundation repair?

Foundation repair targets walls, slabs and soil systems that hold the house. Post-and-beam work targets the interior load path under floors — columns, pads and the beams they carry. They meet when pads fail because of water or soil movement; a good assessment says which problem is primary so you do not buy the wrong trade first or stack temporary posts as a permanent foundation strategy.

What photos help before a post-and-beam visit?

Wide shots of the crawl or basement showing the post line, close-ups of bases and pads, any water stains, and upstairs symptoms (door rubs, floor slope). Note recent flooding or plumbing leaks. Pattern beats a single scary photo of one rusty column.

How urgent is a crushed post base?

Urgency depends on remaining section, load above, and whether movement is active. A clearly crushed or leaning post under a main beam is not a wait-until-spring cosmetic item — shore and schedule permanent repair. Borderline soft wood still needs a dated plan, not infinite monitoring without triggers.