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.
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.
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 →
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 forA 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 forMajor 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 forBottle 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 forSistering 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 forNew 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 forReplacing 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 forStructural repair with no interest in the leak or grade problem that caused the rot. The next post will fail the same way.
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 →
If the number is the problem, here are the ways people pay for it →
HomeMatchup does not perform post and beam repair. We match you with licensed local structural repair pros for post and beam repair. Free for homeowners — Get matched free · how we verify pros.
When post and beam repair is the wrong call
When saying yes is the wrong move:
- 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.
Types of post and beam repair
| Option | What it means for you |
|---|---|
| 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. |
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.
Post and Beam Repair near you
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Sources
Sources last checked
- International Residential Code overviewInternational Code CouncilRetrieved 2026-08-04Model code framework structural repairs are inspected against locally.
- Occupational Employment and Wages — Construction TradesU.S. Bureau of Labor StatisticsRetrieved 2026-08-04Labor cost context for home-services trades nationally.
Sources for figures and claims on this page.
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