Window Replacement in an LP SmartSide House — Trim Boards and Flashing
A house sided in LP SmartSide, maybe only a few years old, with builder windows that fogged or leaked, and trim that has to go back on the way the siding maker says.
Reply within one business day. Or call / text 763-204-2099.
Window replacement in an LP SmartSide house follows the siding maker's details: the lap is cut back around the opening, the new window's flange is flashed to the house wrap, new SmartSide trim boards go on with a drip cap over the head, and the cuts get the factory color. JMB Builders does it across the Twin Cities metro. Priced per window, quoted from photos or at a free in-home estimate, with a reply within one business day.
- Priced per window, insert or full-frame
- New trim boards with a drip cap, gapped and sealed
- Cut edges sealed and factory color touched up
LP SmartSide is the engineered wood lap and trim on most new houses around the Twin Cities since the mid-2000s, and on a lot of re-sided older ones. The windows in a SmartSide house sit behind the lap with a nailing flange, and the trim is SmartSide trim boards, four inches or so wide, butted to the lap with a gap and sealant. The whole system depends on the cut edges being sealed, the trim gapped off the window and the head trim flashed with a drip cap.
When the windows are replaced, that detail is rebuilt. The lap is cut back a set distance from the new trim, the old window and trim come out, the new unit is set with its flange over a sill pan and taped to the wrap. New trim boards go on, with a metal drip cap over the head trim and a gap at the sill so water drains. Every cut edge is primed and the trim and nail heads are touched up with the siding maker's factory color, which comes in a can for exactly this.
Where the frames are sound and the trim is good, an insert keeps the trim and only the stops change. Where the builder set the windows without a drip cap or without sealing the cuts, the trim is often swollen at the corners and full-frame with new trim is the right call. Interior painting is quoted as a separate line — or leave it primed and caulked and paint it yourself.
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
- Your pick of window style, exterior color and glass
- The siding and trim color name from your builder or the siding job, if you have it
- Photos of each window from outside with the trim boards in frame, one from inside, and a close-up of the trim corner at the sill
- Your interior paint color if you want us to finish the inside trim
What JMB supplies
- In-home measure of every opening before anything is ordered
- The windows, ordered to size
- Old windows and trim boards out and hauled away, lap cut back cleanly
- Rot repair at the sill and sheathing (quoted from the photos)
- Sill pan, flashing tape at the jambs and head lapped to the house wrap
- New SmartSide trim boards, cut edges primed, with a metal drip cap over the head
- Sealant at the trim-to-lap gap, and factory-color touch-up on cuts and nail heads
- Interior stops, stool and casing, or jamb extensions on a drywall return
- Photos of the finished windows in your job folder
How it is priced: per window
Quoted in writing from your photos, with a reply within one business day. What moves the number:
- Insert with the trim boards kept vs. full-frame with new trim boards and drip cap
- Lap siding vs. panel or board-and-batten SmartSide, which is cut back differently
- Swollen or rotted trim boards and lap courses that have to be replaced around the opening
- Matching the factory color for touch-up vs. a custom-painted siding color
- Rot in the sheathing behind trim that was never flashed
- Number of windows in the job
Send one photo of each window from outside with the trim boards in frame, one from inside, and a close-up of the bottom trim corner. Include the siding color name if you have it.
How long it takes
Full-frame windows in SmartSide lap: three to five a day with new trim and touch-up. Inserts: more. Every opening is trimmed and sealed the day it is opened.
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
Full-frame with new trim boards
Lap cut back, old unit and trim out, new window flashed to the wrap, new SmartSide trim with a drip cap, gaps sealed, cuts and nail heads touched up in the factory color.
Insert, trim boards kept
Where the frames and trim are sound. The new unit sets inside the old frame, the trim stays, and the exterior gap is covered with a trim strip in the window color. The drip cap is added if the builder skipped it.
Swollen trim corners
Trim boards that swelled at the bottom corners because the cut ends were never sealed are replaced with new boards, cut edges primed, set with a gap at the sill so water drains.
Custom-painted SmartSide
On a house that was field-painted rather than factory-finished, the new trim is primed and painted to the house color as its own line on the quote.
Window Replacement in an LP SmartSide House — Trim Boards and Flashing: questions, answered
Can you replace windows in a house with LP SmartSide siding without replacing the siding?
Yes. The lap is cut back a few inches around the window, enough for the new flashing to reach the house wrap and the new trim boards to sit on a clean edge. The lap on the rest of the wall is untouched. New trim boards cover the cut, and the cut edges of the lap are primed and sealed where they meet the trim.
Does new window trim on SmartSide need a drip cap?
Yes. The siding maker calls for a metal drip cap over the head trim board, lapped under the siding above and extending past the trim ends, so water running down the wall goes over the trim instead of behind it. Many builder installs skipped it, and that is why the head trim and the top of the window frame are the first to swell. We add it on every full-frame install and on inserts where it is missing.
Why are the corners of the trim around my windows swollen?
The trim boards were cut and installed without the cut ends primed, and the bottom ends sit tight to the sill with no gap, so water wicks into the board end and the engineered wood swells. The fix is new trim with every cut edge primed, a gap at the sill, sealant at the lap joint and a drip cap at the head. That is how the siding maker says to do it, and it holds up.
How do you match the paint after replacing windows in SmartSide?
Factory-finished SmartSide comes in named colors, and the maker sells touch-up paint in those colors for cut edges and nail heads. If you know the color name from your builder or your siding job, we use it. If not, we match from a sample. A field-painted house is matched to its paint color instead, and the new trim is painted as its own line.
Can new trim boards be wider than the old ones?
Yes, if the lap is cut back further to fit them. Going from a narrow trim to a wider one is a common upgrade at window replacement because the lap has to be cut anyway. The corner boards and other trim on the house should stay in proportion, so we look at the whole wall before suggesting a width.
Is there rot behind the trim on a SmartSide house that is only ten years old?
Sometimes, where the drip cap was skipped and water ran behind the head trim for years. The sheathing above the window and the sill are checked when the old unit comes out. Soft sheathing is cut out and replaced before the new window goes in, and it is quoted when found rather than guessed at in advance.
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.
Related jobs we do
Window Replacement, Vinyl Siding House — Unzip, Flash, New J-Channel
A vinyl-sided house with windows that have failed, and you want them done without a stripe of mismatched new siding around every opening.
Read moreWindow Replacement in a Cedar Siding House — Wood Trim, No Capping
A stained or painted cedar house with wood windows that are done, and you do not want aluminum wrapped over the trim to fix it.
Read moreReplace 1990s Builder Grade Windows — Fogged Glass, Leaking Mulls
The house was built in the 1990s and still has its original windows. Some are fogged, the double hungs will not stay up, and there is a water stain under the big mulled unit.
Read moreLP SmartSide Siding Installation — Engineered Wood Lap and Panel
Engineered wood siding that looks like painted cedar and takes a hailstorm, installed with the sealed cuts, joint flashing and clearances that keep it that way through Minnesota winters.
Read moreExterior Window Trim After New Siding Replacement
The siding is done, the windows are sitting in a thin strip of J-channel, and the house still looks unfinished. We trim them out in boards that shed water and last.
Read more1.5 Story Dormer Window Replacement — Upstairs Knee Wall Bedrooms
The upstairs windows in the dormers are drafty and hard to reach, and the bedrooms up there are the coldest rooms in the house.
Read morePage reviewed October 10, 2026 · JMB Builders LLC, MN license BC809005 · All windows pages
Where we work
Window Replacement & Installation near you
Based in Zimmerman, scheduling across the Twin Cities metro. Closest first: