Shutters for older homes: crooked openings, original windows and lead paint

Updated October 22, 2026

The short version: older openings are rarely square, so measure more than you think you need to and be ready to choose a frame. Keep the original windows if they’re sound. And before you drill, sand or scrape old trim, assume there could be lead paint underneath.

Why older openings are different

Houses move. Framing dries and shrinks in its first years, foundations settle, and a century of paint builds up on the trim. The National Research Council’s digest on wood shrinkage notes that wood in heated buildings swings between about 6% moisture in winter and 12% in summer, and that framing lumber shrinks as it dries^[4]. Over decades that adds up to openings that are a little out of square, a little out of level, and not the same width at the top as at the bottom.

None of that is a reason not to fit shutters. It’s a reason to measure as if you expect it, because you should.

Measure as if it isn’t square

1. Width three times: at the top, the middle and the bottom of the opening. Write down the smallest.
2. Height three times: at the left, the centre and the right. Write down the smallest.
3. Both diagonals, corner to corner. If they differ by more than about ¼ in (6 mm), say so on your order.
4. Depth, from the front of the opening to the glass, the sash lock or the crank, whichever sticks out most. Older windows often have deep sills and chunky hardware.
5. The sill: is it flat, or does it slope to shed water? A sloped or rounded sill changes where a shutter can sit.

The full method, with pictures, is on how to measure.

Inside mount or outside mount

An inside mount sits within the opening and shows off the trim around it. It needs an opening that’s close to square and deep enough for the louvers to tilt. An outside mount sits on a frame fixed to the trim or the wall around the window, and it hides an opening that tapers or leans: the frame is square even when the hole isn’t.

Keep the windows if you can

The US National Park Service, which publishes the federal government’s guidance on caring for historic buildings, “recommends the retention and repair of original windows whenever possible”, and notes that “Wooden windows which are repaired and properly maintained will have greatly extended service lives”^[1]. Its guidance also points out that a repaired historic wood window with a storm window can perform better than a double-glazed metal window without a thermal break^[1].

Here’s the thought worth having before you order replacements: interior shutters work with the window you have. They screw into the frame or the casing, take nothing away, and can come out without a trace beyond a few filled holes. In a heritage home or a heritage district, that reversibility is worth a lot.

If the sills are rotten, though, fix them first. The same brief describes water collecting on sills as a major cause of decay, and suggests probing sound-looking wood with an awl, because rot hides under paint^[1]. A shutter fixed to a soft sill won’t stay square.

Check the window before you order

A shutter is only as square as what it’s fixed to. Manitoba and Winnipeg’s guidelines for windows in historic buildings include a simple condition checklist, and two of its lines are worth doing with a screwdriver in hand: “The window sill shows no sign of rot, cracking or corrosion”, and “The window sill slopes away from the building”^[6].

1. Probe the sill and the bottom of the casing. Press an awl or a small screwdriver into the wood at the corners. Sound wood resists; soft wood is rot under the paint^[1].
2. Look at the slope. An outside sill should shed water away from the house^[6]. Water that pools at the inside corner finds the casing your shutter frame screws into.
3. Open and close the sash. A sash that sticks or a lock that has been painted shut is easier to sort out before a shutter is in front of it.
4. Note the hardware. Old sash locks, lifts and crank handles stick out further than modern ones. They set the depth you measure to.
5. Decide about storms. If you’re adding interior storm windows, which the same guidelines call a good alternative and often cheaper than exterior ones^[6], fit them first and measure the shutter after.

Heritage homes: the standards behind “keep it reversible”

In Canada, Parks Canada publishes the national standards for conserving historic places. Three of them describe the approach that suits interior shutters: “Conserve heritage value by adopting an approach calling for minimal intervention” (standard 3), “Use the gentlest means possible for any intervention” (standard 7), and make new work “physically and visually compatible with the historic place and identifiable on close inspection” (standard 9)^[5]. Standard 9 also says to “Document any intervention for future reference”^[5].

Manitoba’s window guidelines are blunter: “Removing historic windows decreases the heritage value of a historic building and should be a last resort”^[6]. In the US, the National Park Service guidance quoted above says the same thing in its own words^[1].

What that means in practice, as our reading rather than any authority’s ruling:

• Fix frames to the casing or the wall, not to the sash, and never cut or plane original trim to make one fit.
• Use as few screws as the frame needs, in places a filler and a dab of paint will hide if the shutters come out.
• Paint the shutters to suit the trim, so they read as part of the joinery rather than something added.
• Keep a note of what went where: a photo of each window before, and the order sheet, for whoever comes next.

Whether a designation covers interior fittings depends on the designation, so ask your municipality’s heritage office before you start.

A worked example: four tall windows in an older house

Older houses often have tall, narrow double-hung windows. Take four 30 × 60 in openings in our basic build (flat moulding, paint stage 1, 3½ in louvers), from today’s price list:

• One window, inside mount: $330 – $420 in the US, $480 – $600 CAD in Canada.
• The same window as an outside mount, with a frame covering 2 in of trim on every side (34 × 64 in), for an opening that isn’t square: $400 – $500 in the US, $580 – $720 CAD in Canada.
• All four, inside mount: $1,350 – $1,650 in the US, $1,930 – $2,370 CAD in Canada.

The outside mount costs a little more because it’s a little bigger; how far past the opening it goes is your choice. On a house where every opening is a different size, that’s normal: each one is made to its own measurements. Give each window its own line, with its own three widths, three heights and diagonals, and a note when the diagonals differ by more than about ¼ in (6 mm). Price your own in the designer.

Lead paint: assume it’s there

In the US, the Environmental Protection Agency says “Homes built before 1978 are more likely to have lead-based paint”, and that even small renovation jobs can make enough dust to poison a child^[2]. Health Canada says a home “probably contains lead-based paint if it was built before 1960”, and that between 1960 and 1990 the exterior may^[3].

Fitting a shutter means a few screw holes, not a renovation. Even so, in an older home:

• Keep children and pregnant people out of the room while you drill.
• Hold a damp cloth under each hole to catch the dust, and wipe up with damp cloths rather than sweeping.
• Don’t sand, scrape or plane painted trim to make a shutter fit. Choose an outside mount or a frame instead.
• Health Canada advises against sanders, heat guns and blowlamps on lead paint^[3]. If you’re doing more than screw holes, the EPA recommends a contractor certified in lead-safe work in pre-1978 homes^[2].

What the census says about your city

Each of our city pages shows how many of that city’s homes were built before 1980 (in Canada, in 1980 or earlier), from the US Census Bureau or Statistics Canada. If the share is high where you live, the chances are good that your openings have a story to tell, and worth measuring twice.