How To Trim Out A Basement Window
Synopsis: Montana architect and remodeling contractor Chris Whalen displays his method for building out jambs to accommodate windows in thick walls. Chris starts by building a deep stool extension, then cuts and attaches the stool. Then, using biscuit joints, he attaches the tiptop and side jambs with an offset. Finally, Chris completes the work past attaching the head casing.
Cease carpentry is the fine art of making rough stuff await good. Even trimming a window can be a challenge because it'south ordinarily complicated by poorly aligned framing or uneven drywall. If things go well, you tin tenderize the drywall with a hammer or shim the window into alignment. If not, the window jambs might need to be planed, the casing tweaked, or the miters dorsum-beveled at odd angles. In the end, a dewdrop of caulk is often needed to disguise the solutions.
Multi-unit windows in thick walls, such equally the basement windows featured here, are prone to even more problems. For starters, even if the windows were installed plumb, level, and square, they might not be parallel with the finished wall surface, significant that the side jambs need to be tapered. Second, the individual units might not be installed in a straight line, significant that the stool needs to exist tapered. Third, access between the window and the interior-wall framing could exist limited, which reduces options for attaching extension jambs.
Remove the narrow stool extension, and build a deep i
Outset, identify the issues
The three window units here are in an eight-in.-thick concrete wall. A two×4 wall covered with drywall sits inside. Earlier casing is practical to a window similar this, the jambs and the stool need to be extended.
The first thing I practise is determine how the window sits in relation to the drywall. With a multi-unit window such as this one, I identify a long straightedge along the top and bottom jambs to determine if the units are in the same plane and at the aforementioned elevation. In this case, the windows were at the same height, only the eye unit of measurement was pushed out in relation to the flanking units. Next, I straddle the corners of each window unit with a brusque straightedge on the drywall and measure from the window jamb. This tells me how wide the extension jambs will exist and if tapering is required. For reference, I write the measurement on the drywall along the edge of the opening where the trim will cover it later. If the variation is less than ane ⁄ 8 in., there's no need to worry about tapering the extension jambs or stool. This discrepancy can exist taken up by tipping the casing slightly. If the difference is greater than 1 ⁄ 8 in., the jambs demand to be tapered.
Fit the stool
With the deep stool assembled, scraped, puttied, and sanded, I turn to fitting. Ultimately, the stool needs to exist tight to the window frame and drywall, and notched around the mullions. This begins with positioning the stool exactly parallel to the window and ends with a slight back bevel on the final cut. Rough- and last-scribing, cutting, and fine-tuning come between.
Solutions start with the stool
Many windows take factory-applied 2-in. extension jambs that make the window suitable for a 2×half dozen wall. For basement walls, y'all demand to extend the side and head jambs fifty-fifty more. I do this with a simple offset biscuit joint. This offset joint looks proficient on the jambs, but it's impractical for a stool. That's why I carefully remove the factory-applied stool extension and replace it with a new total-depth stool.
The new stool needs to fit betwixt the rough opening in the framed wall while extending past the side casings. The overall length of the stool is the sum of the distance between the side jambs, the width of the casings, the cas ing reveals (typically 1 ⁄ 4 in.), and the amount of overhang beyond the casings. Subsequently cutting the stool to length, I miter the ends so that the profile returns to the wall. The extension is biscuited and glued to the back of the pro filed stool. When this associates is dry, I scrape excess glue, sand, fill gaps, and sand again, making it fix to install.
Gear up the new stool in the opening, and check its fit. The width volition probably need adjustment. Because the three private window units weren't perfectly in line on this project, I needed to taper the stool in addition to notching around the mullions. I use a foursquare and a scribe to measure and mark the notches and the ends of the stool extending past the window. After removing excess cloth with a jigsaw, I slide the stool into position again for final scribing and planing. Finally, I bore for pocket screws, clamp the stool into position, and spiral it to the window frame. I use a lot of screws (every 6 in. to ix in.) because someone is going to sit on this window stool quondam in the hereafter, and I don't want it to pause.
Install jamb extensions with an offset reveal
For the head and side jambs, I add together a slice to the factory extensions using an start reveal of about i ⁄ 8 in. The head jamb needs to be long enough to pass the side jambs, only it does not have to be fit to annihilation else. I cut it slightly longer than the overall length of the window. To scribe the head jamb, I ready it in place with bar clamps and shims. Next, I mensurate at a few spots to decide what needs to be removed from the jamb stock, and I fix the scribe and marking along the length of the jamb. I cut to the scribe line with a pocket-sized circular saw, then use a power planer, a block plane, and a sanding block to adjust until the fit is acceptable. As with the stool, the process takes a couple of fittings.
At this point, I use a biscuit joiner to create a consistent get-go or reveal betwixt the extension jamb I'yard making and the one applied past the factory.
On the project here, because in that location wasn't as much clearance betwixt the window frame and the crude framing on top of the window as there was on the stool, pocket screws wouldn't work. Instead, after applying glue and inserting the biscuits, I shimmed and nailed the caput-jamb extension in place, making sure it was foursquare to the side jambs.
The only difference in installing the side jambs is that the length needs to fit precisely between the new stool and head jamb. Rather than bending my tape measure into a corner, I measure in two steps: up from the stool twenty in., and then downward from the head to the 20-in. mark. I then add together the two numbers together. I cutting the jambs to length and so to width according to the numbers written previously on the drywall. Finally, I fit the pieces then biscuit, shim, and nail them in place, making sure they are foursquare and tight to both the head jamb and the stool.
Fit the superlative and side jambs with an offset
For a peachy-looking joint that's fast to fit, I use a beige joiner with a clip-on outset plate. A one⁄8-in. offset adds a shadowline to the profile and eliminates all the fussy fitting, sanding, and patching that a flush fit tin can require.
Clamps prop the top jamb for scribing. Just similar the stool, the top extension jamb needs to be scribe-fit to all three window units. Don't become bogged downwardly trying to get the exact length; information technology just needs to be long enough to 
country on the side jambs. What's of import is that the height extension is parallel to the interior-wall surface when you scribe (1) . Scribe the back edge along the window frame (ii) , setting the scribes to the biggest distance that the front border of the jamb sticks out past the drywall. Because the framing wasn't held dorsum enough from the window, I had to face-nail the head and side extensions into the framing (3) rather than using pocket screws. The side jambs need to fit tightly tiptop to lesser and also forth their width (4) . If the framed wall isn't as plumb equally the foundation wall (or as out of plumb), the board needs to be tapered. To get a tight fit pinnacle to bottom, I measure in two steps. Beginning, I make a marker xx in. upwardly from the stool. Next, I measure out down to the mark, and I add the two numbers together. This is more than accurate (and faster) than bending my record into a corner and guessing at the exact measurement.The rest is standard procedure
The rest is standard procedure
The final few steps of the process aren't much different than regular window trimming: Apply the mullion trim, casings, cap, and frock. I beginning with the mullions and piece of work my way out. Using the same two-step measuring technique as I did with the side jambs, I measure the mullions, then cut and blast them in place.
I cut side casings to length, making them 1 ⁄ four in. longer than the altitude between the stool and caput jamb, thereby creating a reveal at the head. Subsequently nailing them in place, I measure out, cutting, shim, and install the head casing and cap. Earlier installing the apron beneath the stool, I permanently shim and cake the stool and so that it is level, straight, and solid. I and then make an apron with mitered returns on the ends the same length as the head casing, and I nail on the apron so that its ends are in line with the exterior edges of the side casings.
Whether y'all're trimming a basement window or ane in a double-stud, adobe, straw-bale, insulated-concrete-grade, or any other thick-wall structure, these techniques ensure a quality installation for an appealing assembly.
Complete the assembly
The trim detail here was dictated by the trim in the existing house. I brainstorm with the mullions, which demand to fit tightly between the stool and the head extension. The side casings are cutting i⁄iv in. long to establish the reveal for the caput casing. The apron is installed last.
Chris Whalen is a partner in Black Mountain Com pany, a abode-building, renovating, and woodwork ing firm in Missoula, Mont. Photos by Daniel S. Mor rison.
From Fine Homebuilding #189
Source: https://www.finehomebuilding.com/project-guides/finish-trim-carpentry/trimming-a-basement-window
Posted by: thomasgove1986.blogspot.com
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