4 steps to a new threshold

How a moderately handy cottager can build a replacement

By David ZimmerDavid Zimmer


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A cracked or rotted door threshold is easy to ignore; just step over the thing, slam the door, and it disappears. But ignore it at your peril. A damaged threshold might keep rain and snow out of the cottage, but there’s a good chance it’s not preventing moisture from seeping into the substructure beneath, which could mean costly and invasive repairs down the road. Fortunately, replacement is a task the moderately handy cottager can accomplish on a shed or the boathouse in about half a day. (If the solid mahogany threshold under your main entry door — rescued from a Tuscan monastery and cherished as a family heirloom — is damaged, you’ll probably want a higher level of joinery. Call someone who does this for a living.)

1. Take measurements

Resist the urge to start ripping and tearing and take some careful measurements. You want to know the thickness and width of the threshold, the inside distance between the vertical jambs, and the overall length, including the “horns” that wrap around the jambs on the outside of the door. Note any wooden doorstops or weatherstripping on the threshold as well.

2. Out with the old

There are two ways to destruct an old threshold. One is to make cuts as close to the jambs on either side as possible with a circular saw set to the exact thickness of the threshold, pull out the piece in the middle, then use a hammer and chisel to split the ends remaining under the jambs into little pieces. You can then use a hacksaw or a reciprocating saw to cut off any exposed nails or screws, taking infinite care not to damage the jambs or the door trim. The second, preferred method, is to remove the threshold in two large pieces that you can use as a template for the replacement. Make one saw cut in the centre, then use a reciprocating saw to slice through the fasteners holding the jambs. Use a flat pry bar to lift the threshold – you might need to cut some more nails or screws – and gently wiggle the pieces free.

3. In with the new

Clean the exposed subfloor, scraping away any adhesive or caulking you might find, then let dry and liberally apply wood preservative over the entire sill area. Transfer your measurements onto a new piece of stock; pressure-treated wood is perfect for this application, but you can also use rot-resistant cedar or fir. Cut the new piece to size with a circular saw, then carefully cut partial notches for the horns, finishing them with a hand saw. With luck, your old threshold will have been made from standard two-by material. If it was too thin, you’ll need to trim the bottoms of the jambs on either side to fit the replacement. If the old threshold was made from thicker material, you’ll need to shim the new one so it fits snugly.

Test fit the new threshold, tweaking it here and there with a hand plane until it fits just right and the door swings into place without either binding or leaving a huge gap. Pull it out again and, with your original as a template, use a hand plane to shave the front face and edge to create a slope so water will run away from the door.You are now ready for final installation. Nails or screws ultimately act as conduits for water penetration, so the fewer fasteners you use, the better. Lay down a few beads of construction adhesive, then slide your new threshold into place. If any adhesive squeezes out where it shouldn’t, wipe it up right away with mineral spirits. Construction adhesive’s iron grip should be all you need to keep the threshold in place, but for extra insurance you might want to add a couple of long nails or screws, one on either side of the threshold close to the jambs. Make sure they are countersunk and cover the heads with waterproof wood filler. If your new threshold isn’t quite thick enough, smear some cedar shims with adhesive before tapping them in, being sure to place a shim directly beneath each jamb, with a couple more to support the middle.

4. Waterproof the threshold

Almost done. Apply a thick bead of exterior caulking over any joints that could admit water, paying particular attention to the joints around the horns. If you’ve shimmed, cut the shims flush and either caulk the gap (if it’s less than 1⁄8″) or apply some quarter-round trim to hide the void, then caulk. Waterproof the threshold with exterior paint, a penetrating stain, or a clear finish — whatever matches the rest of the door. When it’s dry, you can step through and slam the door on another cottage project.

This article was originally published on March 20, 2006

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David Zimmer