Wallingford, Seattle Addition Siding — Hardie Lap, WindsorONE Trim & Custom Corbels Matched to the Original House

Additions are where a lot of Seattle exteriors go wrong. The framing is fine, the windows are fine, and then the siding shows up as a slightly different lap, a flatter trim, a porch with no brackets — and from the sidewalk the new wing looks exactly like what it is. This Wallingford craftsman got the opposite treatment. The homeowner built an addition with a new covered porch, and our job was the whole exterior package, matched to the original house: smooth James Hardie lap siding at the existing reveal, a porch gable in HardieShingle cut to two custom sizes, WindsorONE trim with the same casing-and-backband profile and bellyband, a new beadboard soffit, custom corbels made to match the originals, wrapped porch columns, a TimberTech composite porch deck with new railings, and R-6 continuous exterior insulation over Benjamin Obdyke HydroGap drainable housewrap — through to paint.

Matching an addition to a Wallingford craftsman

Wallingford is one of Seattle’s best-preserved craftsman neighborhoods, and the original house here had all the signatures: lap siding on the body, shingles in the gables, deep window casings finished with a backband, a bellyband breaking the wall, and bracketed porch posts under a beadboard ceiling. Every one of those details had to come back on the addition — new, straight, and in the same proportions — or the two halves would never read as one building.

So before any material was ordered we measured the house: the lap reveal, the width and thickness of the casings, the backband profile, the height and build-up of the bellyband, the size and angle of the porch brackets. That list became the spec. Matching is not a look you buy off the shelf; it is a takeoff.

HydroGap first, then R-6 exterior insulation

New walls in Seattle have to meet a far tougher energy code than the 1920s house they attach to, and the cleanest way to get there without fattening every framed wall is continuous insulation on the outside. We dried the addition in with Benjamin Obdyke HydroGap — a drainable housewrap whose built-in spacers keep a drainage gap against the sheathing — and then ran R-6 rigid exterior insulation over it, seams taped, before a single course of siding went on.

That order matters. With the drainage plane on the sheathing, any water that ever gets behind the cladding runs down and out on the HydroGap, and the insulation outside it keeps the sheathing warm enough that it never becomes the condensing surface. It is the same wall we built on our Green Lake Hardie re-side, just on new framing instead of a tear-off.

James Hardie lap, WindsorONE trim and backband

The cladding is smooth-face James Hardie lap siding, hung at the same reveal as the original house so the course lines run straight from old wall to new. Fiber cement gives the addition what the original wood never had — a siding that does not swell, feed rot, or depend on a perfect paint film — while holding the exact shadow lines a craftsman elevation depends on.

The trim is where most additions lose the match, so all of it here is WindsorONE: finger-jointed, kiln-dried, factory-primed exterior trim made in the classic profiles older Seattle houses were built with. Window and door casings got the original house’s backband; the bellyband was rebuilt at the same height with the same cap so it wraps the addition and lands on the existing wall without a step. Primed stock that stays straight is also what keeps the paint line crisp for years instead of one season.

Beadboard soffit, wrapped columns and custom corbels

The porch is what sells the match. Its gable is HardieShingle — but the original house’s shingle pattern is not a stock exposure, so we cut the panels to two custom sizes to reproduce it in fiber cement. Its ceiling and soffit are new beadboard, and the posts and beams were wrapped in trim to the same section as the original porch. The corbels — the angled brackets where each column meets the beam — were not available in the original size, so we made them in the shop to match, then primed and painted them with the rest of the trim. None of this is structural. All of it is why the addition looks like it was always there.

The porch floor and steps are TimberTech composite decking with new white railings — the same material we install as a TimberTech deck builder, chosen here so the one part of the exterior that takes foot traffic and standing water never needs to be stripped and re-stained. One crew did the whole exterior, wrap to paint, which is how the colors, reveals and trim lines all landed in one scheme.

The takeaway

An addition does not have to announce itself. Measure the original house, build the new wall to today’s standard — HydroGap, continuous insulation, fiber cement — and then put the craftsman details back on with trim stock that will actually hold paint. This one reads as original from the street, and it is warmer, drier and lower-maintenance than the house it matches.

If you are planning an addition, ADU or DADU in Wallingford or anywhere in North Seattle and want the exterior to match the house, that is exactly what we do as a Seattle siding contractor — and we can re-side the original at the same time if you want the whole house done.