Siding Repair in Northgate

Northgate is block after block of post-war tract housing on flat lots with shallow eaves, much of it re-sided once already in the 1970s or 80s with material that is now at the end of its life. Thornton Creek and its ravines keep ground-level moisture high across the whole area.

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Why Northgate houses fail the way they do

Northgate sprawls across North Seattle from the light rail station east to Lake City Way, defined by flat lots, wide streets, and block after block of post-war tract housing built rapidly in the 1950s and 60s. Proximity to Thornton Creek and its tributaries means persistent ground-level moisture, while shallow eaves on rambler-style homes leave siding almost fully exposed to driven rain.

The dominant form is the single-story rambler or split-entry home — modest 1950s-60s tract houses originally sided with cedar bevel, T1-11 plywood panels, or hardboard products like Masonite. Many were re-sided in the 1970s-80s with materials that are now failing. The neighborhood also has pockets of 1990s-2000s townhomes near the light rail station and North Seattle College.

Hardboard swelling and delamination is the dominant repair. It shows at the bottom edge of each course first, then at every nail, and it accelerates once the paint film breaks. There is no restoring it, so the honest conversation is which elevations have gone and what replaces them — fiber cement and engineered wood both solve it permanently on this housing type.

T1-11 plywood panel is the other Northgate material, and it rots from the base up where the panel meets grade. Because the vertical grooves channel water sideways, the damage is usually wider than it looks. We cut back to a sound joint, correct the clearance at the bottom of the wall, and flash the panel edge properly rather than relying on sealant.

Landmarks we work around here: Northgate Mall (currently under redevelopment), North Seattle College campus, Northgate Community Center and pool and Thornton Creek and its wooded ravines.

How rot gets into a Northgate home

Hardboard Siding Swelling and Delamination

Thousands of Northgate ramblers were re-sided in the 1970s and 80s with Masonite and similar hardboard products, which looked good initially but absorb moisture like a sponge. After 40+ Seattle winters, these sidings are swelling at the edges, delaminating at base courses, and rotting where ground moisture wicks up. Hardboard cannot be patched — once it begins to fail, full-wall replacement with LP SmartSide or fiber cement is the only durable fix.
T1-11 Plywood Rot at Base Courses

Many original Northgate ramblers wear T1-11 grooved plywood panels, a popular 1960s-70s siding that looks solid until you probe the bottom two feet. Proximity to Thornton Creek and poor lot drainage cause the plywood to absorb ground moisture, delaminate, and rot from the base up. We routinely find rotted rim joists and sill plates underneath, requiring structural repair before new siding goes on.
Cedar Bevel Siding Splits on South Elevations

Ramblers that retained their original cedar lap siding often show deep radial splits on south-facing walls after six decades of UV exposure. These splits admit water behind the siding, soaking the sheathing and causing hidden rot that only becomes visible when boards are removed. We splice in matching bevel cedar where splits are isolated, or recommend full-wall replacement when damage is widespread.
Trim Failure Under Shallow Eaves

Northgate ramblers have minimal eave overhangs — often just 12 to 18 inches — leaving fascia, rake trim, and the top courses of siding almost fully exposed to rain. Over decades, this exposure causes fascia boards to rot, paint to peel, and water to infiltrate the wall at the roof line. We rebuild rotted fascia and install drip edge and proper flashing before re-siding to prevent the cycle from repeating.

What we rebuild with in Northgate

Three materials, chosen for how they behave on a wall that stays damp — not for what is fastest to hang.

Not sure which one belongs on your house? The materials comparison lays out the trade-offs, and the siding repair page for Seattle covers how we work citywide.

Seeing something on a Northgate wall you cannot place?

Describe it or send a photo. We will tell you whether it is a board, a section, or something structural before anyone books a visit.

Mon–Fri, 7:00am – 5:00pm

(425) 517-1751

Siding Repair near Northgate

Worth reading before you decide

Who is coming out

Seattle Trim Repair

8338 20th Ave NW
Seattle, WA 98117

(425) 517-1751
Mon–Fri, 7:00am – 5:00pm

Our shop is in Ballard, so Northgate is a local run rather than a trip across the region. Find us on Google Maps.

Book a Northgate inspection

Free, no obligation, and you get a straight answer about what the wall is actually doing. Same-week scheduling on most repairs.

(425) 517-1751 Free Estimate

Mon–Fri, 7:00am – 5:00pm · Free estimates · Same-week scheduling

Northgate questions we get asked

My 1960s Northgate rambler has T1-11 siding. Can I just replace the bottom section where it is rotted?

T1-11 is manufactured in full-height 4x8 or 4x9 sheets, and splicing in a partial section creates a visible horizontal seam that looks unintentional and invites water infiltration. More critically, when the base of a T1-11 panel is rotted, the rim joist and sill plate behind it are almost always damaged as well — ground moisture does not stop at the siding. We recommend removing the full panel, inspecting and repairing the framing, and replacing with a durable material like LP SmartSide.

How much does it cost to replace the siding on a typical Northgate rambler?

A single-story 1,200-1,500 square foot Northgate rambler typically costs $15,000 to $28,000 for full siding replacement, depending on the material selected and the condition of the underlying structure. LP SmartSide engineered wood runs at the lower end of that range and is a popular upgrade from failing hardboard; James Hardie fiber cement costs more but offers the longest lifespan. Homes near Thornton Creek often require additional rot repair, which can add $2,000-$5,000 to the project.

Is it worth upgrading the house wrap when I replace the siding on my 1950s rambler?

Absolutely. Most Northgate ramblers were built with nothing more than tar paper behind the siding — no drainage plane, no modern weather-resistive barrier. When we remove old siding, we install a drainable house wrap like Tyvek DrainWrap and add pan flashing at every window and door. This upgrade adds minimal cost to the project but dramatically improves moisture management, protecting your new siding investment and preventing the hidden rot that destroyed the original wall.