Eclectic Homes

How to Replace Window Trim

December 25, 2018

Whether I am flipping through a magazine or viewing the latest house series on TV, I am always drawn to a home’s trim. I really like the way the use of different architectural trim elements can totally change the feel of the entire house. Sometimes that may be useful, and sometimes it can be completely awful.

Once we replaced our obsolete and wallet-busting single-pane aluminum windows using energy-efficient double-pane vinyl windows in our kitchen nook, I began dreaming of adorning the windows with lovely trim. I had been excited for the end result, but because I am always so focused on trim in other people’s houses, I was totally terrified about actually picking the trim and placing it set up in my house.

Meg Padgett

The possibilites for trim are positively endless. I wanted to keep things pretty simple for our 1900 cabin-style residence, but I also wanted to allow the trim draw the eye and also showcase our opinion to the backyard. I have lost in all the choices online. So I pulled back, checked out our regional home store and went with my gut. Fortunately, I found installing the trim to be a much easier process than choosing it.

Lingo to know:
Interior jamb:The vertical sides along with the flat top of a windowCasing (or case molding): The decorative trim mounted round the windowStool or ledge: The flat bottom section of this windowApron: The casing mounted beneath the fecesPlumb: At a vertical or vertical line

Meg Padgett

Here’s the way we substituted our window trim.


Paint-grade fiberboard casing
Paint-grade 3-inch medium-density fiberboard (MDF)
Paint-grade 3 1/2-inch MDF
2 1/2-inch rosette corner blocks
Miter box or miter saw
Measuring tape
6D 2-inch finish nails
Wood shims
Nail set
Paintable caulk

Meg Padgett

If you’re replacing trim on existing windows, then remove all the trim down to the rough opening with a small pry bar.

Hint: To avoid damaging your walls when prying the trim off, place a large putty knife between the pry bar and the wall.

If you have just installed windows, then you’re good to go. Begin by measuring the duration and thickness of the bottom of the rough opening to ascertain the size for the stool.

Meg Padgett

Since we proposed to paint our trim white, we utilized preprimed MDF for the feces and jambs. We utilized 3 1/2-inch MDF for the stool and cut it to have a 3/4-inch extension beyond the interior casing.

If a natural wood look is more your style, use solid wood trim, for example Hemlock, in area of MDF.

Meg Padgett

Use a miter box or miter saw to trim all the trim pieces to the desired length.

For the interior casing, we utilized rosette corner blocks, so the demand for slightly harder angled miters has been eliminated. If a mitered corner is more up your alley, use the miter box or miter saw’s guides for quick and precise angled cuts.

Meg Padgett

Put the stool within the opening and make sure that it’s level. If necessary, use shims to level the feces. Attach it to the window’s base with 2-inch finishing nails.

Meg Padgett

Assess the side jambs from the top of the stoop to the peak of the opening and cut to that length. We utilized 3-inch MDF for the head and side jambs. Ensure that every side jamb is plumb and level — if needed, use shims — and attach each with 2-inch finishing nails.

Note: Shims need to be trimmed prior to attaching the casing. You can achieve it simply by hitting one using a hammer, or you may want to saw off them when more than one is used.

Meg Padgett

Gauge the distance from every side jamb on peak of the opening. Cut the 3-inch MDF to this length. Ensure the head jamb is plumb and level — if necessary, use shims. Install the head jamb using 2-inch finishing nails.

Meg Padgett

Together with the interior jambs and stoop set up, install the casing.

If utilizing rosettes, install those first. We placed our 2 1/2-inch rosettes plumb together with the interior side of the side jamb, in the end of the head jamb and about 1/4 inch from the top of the two. Ensure that the rosette is plumb and square before securing it by 2-inch finishing nails. Adhesive may also be used to install the rosette.

Install the casing. Assess the distance between the stool and the rosette for the sides and between the two rosettes for the mind. Cut each slice of casing to the specific length for every measurement. Typically, the casing is connected using a little part of the jamb visible. We placed our casing with all 1/4 inch of this jamb visible. Make sure that every piece is plumb to the positioning you’ve chosen and join with 2-inch finishing nails.

Use a nail set to countersink all the claws on the trim.

Meg Padgett

Install the apron below the stool. Typically, the apron is the casing turned upside down, and that’s what we have done.

Measure the length from side casing to side casing to ascertain the period of the apron. Cut and install the apron, ensuring that it is level and plumb with the outside dimensions of each side casing. There are numerous techniques to finish the ends of the apron; we left our ends blunt.

Another window trim element is the cove mould, which can be connected to the apron only under the feces, but we opted to forgo that element.

Meg Padgett

With all the trim in place, fill any gaps and nail holes with paintable caulk.

Meg Padgett

When the caulk has dried, paint the trim. I used 2 coats of Behr semigloss white. I added Flood Floetrol, a paint additive that reduces the appearance of roller and brush marks. Read the manufacturer’s label for mixing recommendations.

If you’re using hardwood trim, apply stain or a polyurethane sealant.

Meg Padgett

Stumped on what proportions you need to use for installing architectural trim in your house? Check out architect Bud Dietrich’s helpful tips.

Meg Padgett

Rosettes are a traditional trim element that were often used throughout the Victorian age but fit in effortlessly in the current traditional home. Much like with casing, there are a multitude of designs, finishes and sizes to pick from.

Meg Padgett

With all the choices on the market, picking window trim can be a daunting task — but hopefully you’ll see that installing trim does not have to be.

Guides to residence trim

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