Why Plumbing Repairs Can Cause Foundation Movement
Any time you dig near or under a foundation, you change the soil conditions that have been supporting that foundation for years. The soil gets loosened. It gets exposed to air and moisture. Compaction changes. Sometimes backfill doesn't get packed down properly.
Slab leak repairs are the biggest concern because the work happens directly under the foundation. Tunneling creates voids. Rerouting pipes means trenching. Even spot repairs require breaking through the slab and disturbing the subgrade.
According to the American Society of Civil Engineers, soil disturbance near foundations is one of the leading causes of differential settlement in residential structures. The risk is highest in the first 6 months after the work is completed, while disturbed soil is still settling into its new state.
What You'll Need
You don't need expensive equipment. Most of this stuff you probably already have.
- Tape measure (standard retractable is fine)
- Pencil or fine-point marker
- Blue painter's tape
- A level (4-foot level works best, phone apps are okay for rough checks)
- Phone camera
- A marble or small ball bearing
- Notebook or spreadsheet for recording measurements
- Crack monitors (optional but helpful, about $12 each online)
Total cost if you need to buy everything: maybe $30-40. A fraction of what an undetected foundation shift could cost you later.
Step 1: Establish Your Baseline (Do This Right Away)
Ideally, start this within 48 hours of the plumbing work being finished. You want to capture the current state of everything before any potential movement begins.
Check Every Door and Window
Open and close every interior door in your house. Note which ones work perfectly and which ones stick, drag, or have gaps. Do the same with windows. Write it down. "Master bedroom door: closes fine, no rubbing. Bathroom door: slight rub at top-right corner."
This is your reference. If a door that worked perfectly starts sticking in three weeks, you know something changed.
Photograph Existing Cracks
Walk through every room including the basement or crawlspace. Photograph every crack you can find, no matter how small. Put a ruler or coin next to each crack for scale. Note the date.
Pay special attention to the area directly above where the plumbing work was done. But check the whole house. Foundation movement doesn't always show up right where you expect it.
Mark Crack Endpoints
Take a pencil and draw a small line across the end of every crack, perpendicular to the crack direction. Write the date next to it. If the crack grows past that mark, you know it happened after the repair.
Check Floors for Level
Place your level on the floor in several locations. Check both directions. Note any readings that are off level. You can also set a marble on the floor in a few spots and see if it rolls. Mark where you tested so you can recheck the same spots later.
Step 2: Weekly Checks for the First Month
Set a reminder on your phone. Every week, spend 15 minutes checking the same things.
Door and Window Test
Open and close every door and window again. Compare to your baseline notes. A door that suddenly sticks when it didn't before is one of the earliest signs of foundation movement. Even a subtle change matters.
Dave noticed his door problem at week three. He told me later that if he'd been checking weekly, he might have caught it even earlier.
Crack Comparison
Look at every crack you photographed. Has anything changed? New cracks? Existing cracks wider? Cracks extended past your pencil marks? Take new photos if anything looks different.
This is where good baseline photos save you. Your memory is unreliable. Photos don't lie.
Floor Level Recheck
Put the level back in the same spots. Same direction. Any change? The marble test works too. If a marble that sat still before now rolls, the floor has shifted.
Step 3: Monthly Checks for the Next 5 Months
After the first month, you can back off to monthly checks. Same routine, just less frequent. The highest risk period is the first 3 months, but soil can continue settling for up to 6 months after being disturbed.
Keep your notebook updated. Date every entry. "March 15: All doors working fine. No new cracks. Floor level unchanged." Boring entries are good entries.
If you installed crack monitors, read them monthly and record the position. Any progressive movement in one direction warrants attention.
Step 4: Know When to Call a Professional
Not every small change means disaster. Some settling is normal after soil disturbance. Here is what should prompt a call to a structural engineer.
Call If You See These Signs
- New cracks wider than 1/8 inch
- Existing cracks that have grown by more than 1/16 inch since your baseline
- Multiple doors or windows that suddenly stick when they didn't before
- Visible gaps between the wall and floor or wall and ceiling
- A floor that slopes noticeably more than it did at baseline
- Cracks that keep growing week over week with no signs of stopping
A structural engineer costs $400-600 for a residential evaluation. Cheap insurance compared to the cost of undetected foundation problems.
Don't Panic Over These
Hairline cracks that appear and stay stable are common. Minor drywall cracks near the repair area often result from vibration during the plumbing work itself, not foundation movement. One door that sticks slightly could be seasonal humidity, not settlement.
The key is patterns. One thing changing is a data point. Multiple things changing at the same time, especially concentrated near the repair area, is a pattern worth investigating.
Common Mistakes People Make
After watching Dave go through this and helping a few other people set up monitoring after plumbing repairs, I've seen the same mistakes repeatedly.
Not Documenting Before the Repair
The best time to photograph everything is before the plumber starts. Second best is right after they finish. If you're reading this before your plumbing repair, go photograph everything now. You'll thank yourself later.
Checking Once and Forgetting
You look around once, everything seems fine, and you forget about it. Then six months later you notice a problem and have no idea when it started. Consistent checking on a schedule catches things early.
Assuming the Plumber Is Responsible
This gets complicated. If the plumber disturbed soil improperly or didn't backfill correctly, there may be liability. But foundations also move for reasons unrelated to the plumbing work. Having documented evidence of exactly when changes occurred helps enormously if you need to make a claim.
Overreacting to Normal Settling
Some minor settling of disturbed soil is expected. Not every hairline crack means your foundation is failing. The monitoring process helps you distinguish between normal post-repair settling and actual structural movement. Follow the data, not your anxiety.
What Happened With Dave
Dave's situation ended up being manageable. The door dragging and drywall crack were caused by about 1/4 inch of settlement along a 6-foot section of his slab where the tunnel ran underneath. An engineer looked at it, said the soil was still consolidating, and recommended monitoring for another 3 months before deciding on any repair.
Three months later, movement had stopped. The soil had settled into its new state. Dave paid $350 to have the void under the tunnel area filled with polyurethane foam as a precaution, re-hung the door, patched the drywall, and moved on with his life.
Total cost of the foundation issue: about $600 including the engineer visit. If he'd ignored it and the settlement had continued, he could have been looking at $5,000 to $15,000 in foundation repair depending on how far it went. Monitoring caught it. That is the whole point.