Soft Spots on the Roof — Rotted Roof Decking Replaced
You stepped on the roof, or the roofer did, and it gave like a mattress. Here is what is under that spot and how it gets replaced without a whole new roof.
Soft spots on a roof mean the roof decking under the shingles has rotted. JMB Builders strips the shingles over the area, cuts the rotted OSB or plank back to solid rafters, adds blocking at the edges, installs new sheathing, and reshingles with underlayment tied into the old roof. Across the Twin Cities and north metro, priced per project, quoted from photos within one business day.
- Priced per project, by the sheet of decking
- Rotted OSB or plank cut out to solid wood
- Area reshingled and tied into the old roof
- Quote from photos in 1 business day
- Licensed MN contractor BC809005
A soft spot is decking that got wet and stayed wet. OSB swells and loses its strength first at the edges of each sheet; plank decking rots at the joints and around old nail holes. The water usually came from a known place: a pipe boot that cracked years ago, a valley, a chimney, the eave above an ice dam, or a bathroom fan dumping moist air into the attic all winter.
The repair is simple when it is caught early. Shingles off over the soft area plus a margin, the rotted wood cut back until the saw finds solid decking over a rafter, two-by blocking added where the new sheet edge lands between rafters, new sheathing nailed off, then ice and water membrane or underlayment, and shingles woven back into the old roof. The leak source gets fixed in the same visit, or the new decking rots the same way.
When the soft spots are in several places, the roof is old, or the attic shows black sheathing across whole bays, patching is money spent twice. We say so from the photos and quote the reroof instead.
What you supply
- Photos of the roof from the ground on each side, with the soft area marked or described
- Photos from the attic under that spot if you can get there safely: stains, black wood, daylight
- What you know about past leaks, ice dams or a bath fan that vents into the attic
- Leftover shingles or the bundle wrapper if you have one, for a color match
What JMB supplies
- Shingle removal over the soft area and a margin around it
- Rotted decking cut back to solid wood over rafters or trusses
- Two-by blocking at sheet edges between rafters, and new OSB or plywood to match thickness
- Ice and water membrane or synthetic underlayment lapped under the old paper
- Shingles woven into the existing roof, matched as close as the current colors allow
- Repair of the leak source: pipe boot, flashing, vent or valley
- Debris hauled away and photos of the rot and the new decking in your job folder
How it is priced: per project
Quoted in writing from your photos within one business day. What moves the number:
- How many sheets of decking are rotted once the shingles are off
- Roof pitch and height, and whether the area is on a one- or two-story section
- OSB or plywood versus old plank decking that needs a thickness match
- Rafter or truss damage under the decking
- The leak source that caused it: a pipe boot is small, a valley or chimney is more
- Shingle match: a current color versus a discontinued one
Photos from the attic under the soft spot tighten the quote the most. We confirm the sheet count the day the shingles come off.
How long it takes
One soft spot of a sheet or two: a few hours to a day, including reshingling. Several areas or a steep roof: one to two days.
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 quote within one business day. We only come out to measure first when the job needs a tape measure — no pressure, no games.
- 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
One soft spot, patched
The common one. A sheet or two of decking replaced under a pipe boot, a vent or an old leak, the source fixed, the area reshingled into the old roof.
Rotted decking along the eaves
Ice dams and missing drip edge rot the first few feet above the gutter. The bottom course of decking is replaced along the run, with ice and water membrane and drip edge added.
Soft spots on an old roof
When the shingles are near the end anyway, the decking is replaced as found during a full tear-off instead of patched now and torn off later.
Soft Spots on the Roof — Rotted Roof Decking Replaced: questions, answered
What causes soft spots on a roof?
Rotted decking under the shingles. It comes from a slow leak at a pipe boot, vent, valley or chimney, from ice dams at the eaves, or from warm, moist attic air condensing on the underside of the sheathing all winter. OSB swells and loses strength at the edges first, so soft spots often line up with the sheet seams.
Can you replace rotted roof decking without a new roof?
Yes, when the rot is in one or two areas and the rest of the shingles have life left. The shingles come off over the soft area, the rotted sheathing is cut back to solid wood over the rafters, new decking goes in with blocking at the edges, and the area is reshingled and woven into the old roof. The leak that caused it is fixed at the same time.
Is it safe to walk on a roof with soft spots?
Not on the soft spot itself. Rotted decking can crack or give way under a person's weight, especially OSB that has swelled and lost its strength. Stay off it, take photos from the ground or the attic, and let the repair crew work from the solid decking around it.
Should I patch the soft spot or replace the whole roof?
Patch it when the soft area is small, the cause is clear and the shingles have years left. Replace the roof when there are soft spots in several places, the shingles are curling or bare, or the attic shows black, wet sheathing across many bays. Two patches on a tired roof usually cost more than they save.
How do I know how much roof decking is rotted before the shingles come off?
The attic tells you most of it: dark stains, black or delaminated sheathing and rusty nails around the soft area. From the photos we price a likely number of sheets, and the quote says how any extra sheets found after tear-off are priced. You see photos of what came off before it goes on the trailer.
Will the new shingles on the patched area match?
We match the brand and color when they are still made and use your leftover bundles when you have them. A new patch looks brighter than a roof that has weathered for years and blends over a season or two. When the color is discontinued we pick the closest current one and tell you before we start.
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 for the builders and dealers we sub for. Counts come straight from our job log; no customer names.
Get a written quote for this job
Three photos and a sentence is enough. You hear back within one business day. Or text the photos to 763-204-2099.
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Read morePage reviewed September 26, 2026 · JMB Builders LLC, MN license BC809005 · All roofing pages
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