Can you replace the rotten joists under the deck along with the rim joist?
Yes. When a deck ledger has rotted the rim joist behind it, the deck joists that rotted at the same ledger get replaced or sistered in the same job, on the same permit, with the same shoring. The line we draw is widespread deck rot: if most of the deck frame is gone, that is a deck rebuild, and we say so instead of quoting it.
Along with replacing the rim joist, will you replace any rotten joist under the top deck?
We will, as long as the rot is the kind that came from the same leak. A customer asked us this nearly word for word, and it is the right question, because the two problems share a cause. Water gets behind an unflashed ledger, sits against the house, and rots the rim joist, the ledger and the first foot of every deck joist hanging off it. Fixing the rim and leaving crumbling joist ends on new hangers would be a half job. So the deck joists that rotted at the ledger are cut back to sound wood and sistered, or swapped whole when they are short enough, and the price for each one sits on the same written quote as the rim.
Where we stop is the far end of the deck. A joist rotted at the beam, a sagging outer beam, post bases sunk in dirt, railings that move: those are deck problems, and a deck contractor builds that for a living. We note everything we see with photos so you can hand it to whoever does that work, or we can refer one. On a two level deck the top deck is the one bolted to the house, and that is the level this article is about; the lower level almost always stands on its own posts.
Why did my rim joist rot behind the deck in the first place?
Almost always a ledger with no flashing, or flashing tucked behind the house wrap instead of over it. Meriden has a lot of 1980s and 1990s pressure treated decks that were lag bolted straight through vinyl or wood siding onto the rim joist with nothing between the ledger and the house. Rain and snowmelt run down the siding, hit the top edge of the ledger, and wick into the joint. The rim joist stays wet for months at a time, and untreated spruce framing cannot take that. The ledger itself is usually treated and looks fine from the yard, which is why the rot stays hidden until a home inspector pushes a probe into it or the deck starts pulling away from the house.
The residential code has required ledgers to be flashed to keep water off the house band joist for years. Section R507 of the International Residential Code spells out the flashing, the fastener sizes and spacing, and the rule that the band joist carrying a deck has to be sound and fully supported below. Connecticut adopts that code through the state building code administered by the Office of the State Building Inspector, and Meriden’s building department inspects to it. A new ledger going onto a new rim gets built to that standard, which is the part that keeps you from paying for this twice.
What gets replaced in the same job, and what does not
This is the split we put in writing on every ledger job. Anything in the middle column is on our quote. Anything in the right column is either never excluded or belongs to a deck crew.
| Condition | Handled with the rim joist | When it becomes separate work |
|---|---|---|
| Rim joist soft behind the ledger | Replaced, full depth, to sound wood past the rot | Never. This is the job. |
| Deck ledger board | Replaced and re-flashed with the rim | Reused only if sound and pressure treated |
| Deck joist ends rotted at the hangers | Cut back and sistered or replaced, new hangers | More than half the joists gone means a deck rebuild |
| Deck joists rotted mid-span or at the beam | Noted in writing with photos | Deck contractor scope; we can refer one |
| Floor joist ends inside the house | Sistered onto the new rim in the same visit | Never. Same shoring, same permit. |
| Wall sheathing and house wrap behind the ledger | Replaced for the width of the repair | Never |
| Decking boards, railings, stairs | Removed and reset only where needed for access | Replacement is deck work, quoted separately |
How the job runs, in order
- 1
Probe and mark the scope
A screwdriver along the rim from inside the basement and along the ledger from outside. The quote lists linear feet of rim, the deck joists that need work and the sheathing width.
- 2
Carry the deck on temporary posts
The top deck gets a temporary beam on posts just outside the house line, then the ledger bolts come out and the ledger comes off.
- 3
Shore the floor inside
A temporary beam under the floor joists a few feet in from the wall takes the load off the rim before any cutting.
- 4
Cut out the rim and rotted joist ends
Rim comes out to sound wood past the last soft spot. House joist ends that crumbled get sistered onto the new rim.
- 5
Install the new rim, sheathing and water barrier
Pressure treated rim, new sheathing, house wrap lapped so water runs out and over, not behind.
- 6
Re-attach the ledger per code
New or reused ledger, flashed over the top, lag screwed or through bolted at the spacing the residential code calls for. No nails, no deck screws.
- 7
Replace the rotted deck joists
Joists cut back and sistered, or swapped whole, hung on new galvanized hangers. Temporary posts come out last.
- 8
Inspection and close up
Meriden building inspector signs off, then siding goes back on.
Most ledger jobs in Meriden run two to four days on site. The deck being carried on temporary posts is the part that surprises people; it looks dramatic and it is routine.
What does it cost to do the rim and the deck joists together?
The rim joist side prices off the published cost guide: a rim joist section runs $1,500 to $4,000, or $100 to $180 per linear foot, and the guide already notes that a deck bolted to the rim adds work, because the deck has to be carried while the rim is out. House floor joists that need sistering onto the new rim are $250 to $600 each on the same table. Deck joists are priced per joist on the same quote, and that number depends on three things: how many are rotted, whether a cut back and sister will do or the joist comes out whole, and whether decking has to come up to reach them. Every deck is different, so the deck joist line is a call, not a chart. Send photos of the ledger from outside and the rim from the basement and you get a written range the same day.
Two things move the total more than anything else. A finished basement ceiling under the rim slows the shoring and the cutting. And a second story bearing on that wall means heavier temporary support. Neither is a reason to wait; a rim that is already soft gets softer, and a ledger on soft wood is how decks come down.
What should I ask any contractor before they touch the ledger?
- How will you support the deck while the ledger is off? The answer names temporary posts and a beam. If they plan to leave the ledger bolted on and work around it, the rim behind it stays rotten.
- What goes between the new ledger and the house? Flashing over the top of the ledger, lapped under the house wrap, plus a water barrier on the new sheathing. Caulk is not an answer.
- Which deck joists are on the quote, and which are not? Count them. A quote that says “repair deck as needed” will grow once the decking is up.
- Who pulls the Meriden permit? The contractor, and the inspection happens before the siding goes back.
- Are you registered and insured? Connecticut HIC number and insurance certificates, checked the way our hiring guide walks through.
If this came up on a home inspection, the failed inspection page covers how we scope and price against a closing date.
Deck ledger questions, answered straight
Do I have to take the deck down to replace the rim joist behind it?
Rarely the whole deck. The ledger comes off and the deck gets carried on temporary posts a foot or two out from the house while the rim is replaced. On a two level deck the top deck is the one bolted to the house, so that is the level that gets supported; the lower level usually sits on its own posts and stays put.
Can the old ledger go back on the new rim joist?
If it is sound, pressure treated and straight, yes, with new flashing and new fasteners. Most ledgers that sat on a rotted rim for years have rot of their own at the bolt holes, so a new ledger board is normal and costs little next to the rest of the job.
Does this need a permit in Meriden?
Yes. Replacing a rim joist is structural work and re-attaching a deck ledger is covered by the residential code, so the job gets a City of Meriden building permit and an inspection before the siding closes up. The contractor should pull it.
What if only the deck joists are rotten and the rim joist is fine?
Then you want a deck contractor, not us. We check the rim joist for free and tell you honestly if the house framing is sound. Rot that stops at the deck side of the ledger is a deck repair.
Get the rim and the deck joists priced together
Send a photo of the ledger from outside and one of the rim from the basement. You get a written range off the published guide, with the deck joists counted, usually the same day.