Rotted Subfloor Under Patio Door — Floor, Rim and Sill Pan Repaired
The floor is soft in front of the sliding door, the flooring is buckled, or there is a stain on the basement rim below it.
Reply within one business day. Or call / text 763-204-2099.
A rotted subfloor under a patio door means the door has been leaking at the sill. JMB Builders pulls the door, cuts the subfloor back to sound wood, repairs rotted rim joist and sill plate with the wall supported, adds a sill pan with flashing, and resets the door or sets a new one. We do it across the Twin Cities metro. Priced per project, quoted from photos.
- Priced per project once the rot is opened
- Subfloor, rim joist and sill plate repaired
- Sill pan and flashing added under the door
Most patio doors that rot the floor were set without a sill pan. Water that gets past the sill or the corners of the frame runs into the subfloor, then down into the rim joist and the sill plate on the foundation. It happens slowly, so by the time the floor feels soft, the rot is usually wider than the door.
The fix starts with the door coming out. The flooring is pulled back, the subfloor is cut back until the saw hits sound wood, and the rim joist and sill plate are probed. Rotted rim sections are cut out and replaced or sistered while the wall above is supported. New subfloor is glued and screwed down, and a sill pan with end dams goes in with flashing tape lapped up the sides.
If the old door is square and seals, it goes back in. If it is the reason for the leak, a new door is set in the same visit. The threshold page covers a sill alone; this one is for when the floor under it is gone.
Get a written quote for this job
Three photos and a sentence is enough: a reply within one business day, or ask for a free in-home estimate. Or text the photos to 763-204-2099.
What you supply
- Photos of the door, the floor in front of it, and any stains in the basement below
- Whether you want the existing door reset or a new door
- Flooring to patch back, if you have spare pieces
What JMB supplies
- Door removed and stored, or the old door hauled away
- Subfloor cut back to sound wood and replaced, glued and screwed
- Rim joist and sill plate sections replaced or sistered, wall supported
- Sill pan with end dams and flashing tape tied into the wall
- Existing door reset, or a new door set, sealed and trimmed
- Flooring patched or left ready for flooring; painting quoted as a separate line
How it is priced: per project
Quoted in writing from your photos, with a reply within one business day. What moves the number:
- How far the rot runs past the door in the subfloor
- Rim joist and sill plate damage found once opened
- Existing door reset vs. a new door supplied
- Flooring inside: patch, transition or left for a flooring job
- Deck ledger or exterior trim at the door that is also rotted
- Basement ceiling below that is finished and has to be opened
Rot is found, not predicted. The quote covers the expected repair and lists how added rim or plate work is priced if it is wider once opened.
How long it takes
Most repairs run one to two days with the door reset the same visit. A new door that has to be ordered means the opening is closed up in between.
How your project works
- 1
Send photos, get a written quote
Send three photos of the space and a sentence about what you want. You get a clear, itemized reply within one business day. Prefer a look in person? A free in-home estimate is always an option.
- 2
Pick materials, or bring your own
We help you choose profiles and materials that fit the house and the budget, or match your existing millwork exactly — or you buy the door or trim yourself and we install it. Everything is confirmed before the crew is scheduled.
- 3
Clean, precise installation
The crew shows up on time, protects floors and furniture, and installs with tight joints and consistent reveals. Photos of the finished work go in your job folder.
- 4
Walkthrough and invoice
We walk the finished work with you. If anything is not right, we fix it before we call the job done. Then one invoice, paid by check or direct deposit — no card fees, no payment links.
Situations and options
Reset the existing door
When the door is square and seals and the leak came from a missing pan or failed sealant, it is reset on the new sill pan after the floor is rebuilt.
New door in the same visit
When the door itself leaks or drags, the new one is ordered ahead and set on the rebuilt floor and pan right after the repair.
Rim joist and sill plate repair
When the rot runs into the rim and sill plate, those sections are cut out and replaced or sistered with the wall above supported.
Rotted Subfloor Under Patio Door — Floor, Rim and Sill Pan Repaired: questions, answered
Why is the floor soft in front of my sliding door?
Water has been getting past the door sill or frame corners into the subfloor, usually for years. Most older patio doors were set without a sill pan to catch it. The soft spot is the subfloor rotting, and it often goes into the rim joist below.
Can you fix the subfloor without replacing the patio door?
Yes, if the door is square and seals. It comes out, the floor and framing are repaired, a sill pan goes in, and the same door is reset. If the door is the source of the leak, replacing it at the same time saves pulling it twice.
Is a rotted rim joist under a patio door serious?
It should be fixed. The rim joist carries the wall and the door above it and ties the floor joists together. Rotted sections are cut out and replaced or sistered with the wall supported. It does not get better on its own.
How do you stop a patio door from leaking into the floor again?
A sill pan with end dams under the door, flashing tape lapped up the sides of the opening, and sealant where the door frame meets the pan. Outside, the deck or patio should sit below the sill and slope away from it.
Do you fix the flooring after the subfloor repair?
We patch the flooring in front of the door when matching pieces are available, or leave the new subfloor ready for a flooring job. Painting and trim touch-up are quoted as separate lines.
Does homeowners insurance cover rot under a patio door?
Policies usually treat slow leaks and rot differently from sudden damage. Check your policy and ask your agent. We can document what we find with photos either way.
Recent JMB work, from our job log
59 installs recorded across 30 Twin Cities communities since Dec 2025. Window and door installs for homeowners and the builders we work with. Counts come straight from our job log; no customer names.
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Read morePage reviewed October 9, 2026 · JMB Builders LLC, MN license BC809005 · All doors pages
Where we work
Door Replacement & Installation near you
Based in Zimmerman, scheduling across the Twin Cities metro. Closest first: