Girder, Beam and Joist Repair
Your first floor is carried by a line of wood down the middle of the basement and a row of posts under it. When any link in that chain softens, drops or gets cut through, the floor above reports it. We measure the whole chain before touching one board.
- Free written diagnosis within 48 hours
- Deflection, bearing and column footings measured on site
- 20+ under Chicago floors, 1,500+ homes
Structural work: 25-year transferable warranty
The short answer
Girder, beam and joist repair rebuilds the load path under a first floor. Weak joists get sistered or replaced, a sagging main beam gets reinforced or swapped, and the posts beneath it get reset on real footings. Carpentry is quoted per run once we measure the damage; a replacement support column with a footing runs $1,500 to $3,200.
A floor is a chain, not a surface. Load moves from the subfloor into the joists, from the joists into the girder running down the center of the basement, from the girder into the columns, and from the columns into pads in the ground. Every link has a rated capacity, and every link loses some of it when wood stays damp, when somebody notches a joist for a drain line, or when a post settles half an inch into soft soil. The dip you walk on is the weakest link declaring itself.
What makes this a Chicago problem is the age of the wood and the water around it. Bungalows and two-flats built before the war carry rough-sawn joists over stone or early block walls, and the pockets those joist ends sit in stay damp for weeks after a wet spring. Add a century of plumbing retrofits cut through the framing and a few posts standing on nothing but a brick or a stack of shims, and the sag has three causes at once. Our house leveling overview explains where beam work sits in the larger job.
What makes a main beam or floor joist fail?
Framing rarely snaps. It loses stiffness slowly, gets cut into by other trades, or stops being properly supported from below, and the floor above averages all three.
These are the five causes we find under sagging first floors, roughly in order of how often they show up.
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The wood stays wet
Joist ends buried in a damp block or stone pocket, and girder ends sitting in the same pockets, hold moisture the longest. Wet wood bends further under the same furniture, and past about twenty percent moisture content, decay fungus has what it needs to start eating.
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Somebody cut the framing
Drain lines, ductwork and old knob-and-tube runs get muscled through joists with no thought for where the notch lands. A deep notch in the bottom edge near mid-span removes exactly the fibers doing the work, and the joist begins to hinge at that point.
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The span was always marginal
Plenty of pre-war framing was sized by habit rather than a span table, and a finished basement or a heavy tile floor added later loads it further. The framing does not fail, it just deflects a little more each heating season and never fully springs back.
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The column under it drops
A post standing on a brick, a paver or a pad the size of a dinner plate will press itself into clay that softens every time the basement gets damp. Half an inch at the post shows up as a wide, shallow valley across the rooms above.
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The wall end gives way
Where a girder bears into the foundation wall, mortar erosion, a stair-step crack or settlement at that corner lets the whole beam end travel down with it. That is a foundation problem wearing a carpentry costume, and piers fix it, not lumber.
What it feels like upstairs
- A floor that flexes when someone walks past a full bookcase
- Dishes rattling in a cabinet on the far side of the room
- A gap opening under baseboard along one interior wall
- Doors upstairs that latch in winter and stick in July
- A marble that always rolls toward the same interior line
What it is not
- Squeaks alone, which are usually fasteners, not capacity
- A single hump over one joist, often a subfloor or flooring issue
- Old cracks that have not changed in years, worth a gauge and a season
How does a sagging beam or joist actually get repaired?
The repair is a sequence, not a product. Measure the whole load path, stop the water, take the load onto temporary support, then rebuild the weak link and set it on something permanent.
Here is how a beam and joist job runs from the first visit to the last screw.
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Survey the floor and the wood
We shoot elevations across the first floor to find the low line, then probe joist ends, girder bearing points and post bases with an awl. Soft wood gives the awl away instantly. The survey tells us whether the wood failed or the support under it did.
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Cut off the water first
Replacing framing above a wet floor buys you a fresh set of soft boards in ten years. Seepage at the wall, a leaking crack or a dirt crawl underneath gets its own scope, and that work goes in before the carpentry, not after it.
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Carry the load temporarily
Screw jacks on proper cribbing pick up the girder or the joist run beside the section being worked on. The load has to be off the member before anything is cut, and the temporary posts need real bearing, not a slab edge.
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Sister, splice or replace
A joist with sound ends gets a full-length sister bolted alongside it. A rotted end gets a scab back to solid bearing. A girder that has crushed, split or been cut too many times gets replaced outright, usually in sections carried down the stairs.
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Reset the support and lift slowly
New columns land on poured footings sized for the load, and any lift happens over days in small increments rather than in one afternoon. Then we recheck the elevations to confirm the floor actually moved where the numbers said it would.
What you get
- A written scope naming every member being sistered or replaced
- Elevation readings before and after, not a verbal impression
- Footings poured and cured before load goes back on a new column
- 25-year transferable coverage on piers and structural stabilization
What it costs you
- Access: stored boxes, shelving and ceiling finishes come down first
- Time, because a controlled lift is measured in days, not hours
- Drywall and trim upstairs may move and need a finish trade after
- Carpentry is quoted per run, since nobody can price wood unprobed
Sister the joists or replace the beam?
Both are real repairs and the choice is made by where the capacity was lost. Reinforcement adds strength beside sound wood; replacement is for wood that has run out of service life.
| Sistering and reinforcement | New beam and added columns | |
|---|---|---|
| What it addresses | Individual joists that flex, sag or were notched | A main girder that has crushed, split or lost its supports |
| How the load path changes | The new member shares load with the original | A new member and new posts take the load outright |
| How it is priced | Per run after measuring, since damage length drives it | Per run for the beam, plus $1,500 to $3,200 per column |
| Time on site | Often a single day for a few joists | Several days including footing cure time |
| Disruption above | Usually none if the basement ceiling is open | Furniture off the affected rooms during the lift |
| Can the floor be brought back up | Partly, and only where the ends still bear properly | Yes, in staged increments over several days |
| When it is the wrong call | When the joist ends themselves are soft or crushed | When the girder is fine and only the posts have dropped |
| What has to happen first | The moisture source gets shut off | Footing and soil conditions get verified under each post |
Neither one is the answer when the beam pocket itself has dropped with the wall. That is settlement, and it gets underpinned before any carpenter is useful: see foundation settlement and underpinning.
Not sure whether it is the wood or the posts? We measure the floor, probe the framing and put the finding in writing, free within 48 hours.
What we find under each era of house
Framing practice changed every few decades, so the failure under a 1920s two-flat looks nothing like the one under a 2003 colonial.
Pre-war bungalows and two-flats
Rough-sawn joists in damp masonry pockets, a built-up wood girder, and posts often standing on brick. A century of plumbing retrofits has usually cut through the framing in three or four places along the same run.
Expect sistering plus columns
Post-war block ranches
Steel beam on adjustable pipe columns, most of them set on small pads. The steel is fine; the pads have pressed into clay, so the low line runs straight down the center of the house.
Usually a column and footing job
1980s and 90s poured wall homes
Longer spans, more open plans and beams sized to code but with nothing spare. Later basement finishing and heavy tile upstairs are what push a marginal span into noticeable deflection.
Reinforcement, sometimes a post added
Newer subdivision homes
Engineered lumber and steel columns on poured pads that generally perform. When these floors move, the cause is usually a cut through a truss or joist by another trade rather than age.
Find the cut, repair the memberWhat does beam and joist work cost?
Support work has published numbers: a replacement column with its own poured footing runs $1,500 to $3,200, and where a bearing point has settled, piers run $1,600 to $3,000 each.
| Work | Range | What moves the number |
|---|---|---|
| Push or helical piersper pier | $1,600–$3,000 | Depth to load-bearing strata, access for equipment |
| Urethane crack injectionper crack | $450–$900 | Crack length and width, access to the full height |
Carpentry itself carries no published per-foot price, and we will not invent one. Sistering, splicing and beam replacement are quoted per run after we measure the affected length and probe how far the soft wood travels, because two joists that look identical from the stairs can differ by six feet of rot. Every number we do publish sits on the pricing page.
When your floor does not need structural work
A good share of the bouncy floors we look at are not a capacity problem. Saying so on the first visit costs us a job and keeps the reputation we would rather have.
The floor is springy but level
A floor can meet its span table and still feel lively, especially with a long joist run and no bridging. Elevations flat within a quarter inch across the room mean nothing has moved. Blocking between joists often quiets it for a few hundred dollars.
Comfort, not capacityIt squeaks and nothing else
Squeaks are almost always subfloor fasteners working against a joist edge, which is an annoyance rather than a structural signal. Screws driven from below into the subfloor usually stop them. A flooring contractor handles this cheaper and faster than we would.
Not our workOne joist end rotted under a bathroom
A slow supply or drain leak overhead will destroy a single joist end while every other member stays sound. Get the plumber first, because repairing that joist while the leak continues just resets the clock on the same damage. Replacing decayed framing comes after the water stops.
Plumber firstThe real problem is the ground below
Where the framing sits over a dirt crawl space, the wood is damp because the ground is open. Sealing it stops the cause, and some floors stiffen measurably once the wood dries out over a season. Sagging floors above a crawl space covers that path.
Moisture firstQuestions homeowners ask about beams and joists
Can a sagging floor be jacked back to level?
Often partly, and never quickly. Wood that has held a curve for forty years has taken a set, and forcing it flat in one session tears finishes upstairs and can split the member you are trying to save. We raise in small increments across several days, checking elevations each time, and we stop where the structure tells us to stop. Getting close and staying there beats chasing a perfectly flat number.
Is sistering a joist as strong as replacing it?
For a joist with sound bearing at both ends, yes. A full-length sister fastened on a proper schedule shares the load and restores stiffness, and it avoids demolishing the floor above to slide a new member in. Sistering stops being the answer when the ends themselves are crushed or decayed, because a sister bolted to failing bearing points simply travels down with them.
How do I know whether it is the beam or the columns?
Elevations tell you. If the low line runs the length of the girder and dips deepest between posts, the beam is deflecting. If the low point sits directly over one post, that post or its footing has dropped and the beam is only reporting it. This is the first thing we measure, because the wrong diagnosis means paying for lumber when the fix was a footing, and the upstairs clues in <a href="/basement-foundation-problems/sticking-doors-sloping-floors/">doors that stick and floors that slope</a> help point at which one it is.
Do I need a permit for beam or joist repair?
Structural work usually needs a permit in Illinois, and some municipalities want stamped drawings when a main beam or its supports change. Requirements vary by village, so check with your local building department before scheduling. We pull what the job requires and work to inspection. If a contractor offers to skip the permit to save you time, treat that as information about the contractor.
Will fixing the beam close the cracks upstairs?
Some of them close on their own once the floor comes back up, and some stay open because the drywall and trim have been refastened around the new shape over the years. Plan on a finish trade afterward for taping, trim and paint. Anyone promising that cracks will disappear on their own during a lift is selling optimism rather than describing the work.
Why will you not quote joist repair over the phone?
Because the price depends on how far the damage travels, and that is only knowable with an awl in your basement. We publish column, pier and injection pricing because those units hold steady. Carpentry gets a written per-run number after the measurement visit, which is free within 48 hours. A phone quote for framing repair is a number designed to be revised upward later.
The posts under the beam are half the story
Most center-line sag we measure in the Chicago area traces back to a post standing on an inadequate pad rather than to the beam above it. That distinction changes the scope, the price and the permit, so it is worth understanding before you read anyone else's estimate.
Sagging floors and support columns
Get the load path measured before anyone quotes lumber
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