Chimney Chase Siding Repair Seattle, WA

Chimney chase siding repair is the removal and replacement of rotted or water-damaged siding on a framed chimney chase, the boxed-in wood structure that wraps a factory-built fireplace flue on the outside of a house. It is the single most common chase failure we see in the Puget Sound. Water gets in at the top, runs down inside the wall, and the siding goes soft from the back before anyone notices the paint bubbling on the front.

This page is about siding: matching the new material to the rest of the house, installing the flashing and water-resistive barrier behind it correctly, and fixing the water source above so the rot does not simply return. If your problem is the metal cover on top of the chase, that is covered under chimney chase cover repair and chimney chase cover replacement. If the framing itself has failed and the structure needs to come apart, that is a chimney chase rebuild. Siding repair sits in between: the bones are sound, the skin is not.

James Chimney Sweep has served King, Pierce and Snohomish counties for more than 25 years. We are CSIA certified and licensed, bonded and insured in Washington.

Timing & Safety

When siding repair is necessary, and when it can wait

Necessary now:

• Siding is soft enough to dent with a thumb or is visibly rotted at the corners or bottom edge
• Water stains are showing inside the house near the fireplace
• Daylight or open gaps are visible at the joints or where siding meets trim
• Insects are active in the chase, which almost always means wet wood

Can usually be scheduled, not rushed:

• Paint is failing but the siding underneath is still firm when probed
• Moss or algae is growing on the surface with no soft spots behind it
• Caulk joints have opened but the flashing behind them is intact

The honest rule is that siding damage is a symptom. If the chase cover or the flashing above is still letting water in, waiting turns a siding job into a sheathing job, and eventually into a chimney chase rebuild. Catching it at the siding stage is the cheapest point in that chain.

Safety considerations

A chimney chase is the wall around your flue, so wet rot here is not just cosmetic. Water that rots siding also reaches the metal flue pipe, the firestop at the ceiling and the framing the fireplace is fastened to. Rusted flue sections and saturated framing next to a heat source are a real fire and carbon monoxide concern, which is why we inspect the flue and firestops when the chase is opened up.

• Do not climb on the roof to inspect or patch the chase yourself. Leave roof and ladder work to us.
• Do not side over soft sheathing or fill rot with foam and caulk. It traps water against the framing and hides the problem.
• If the fireplace is gas: if you ever smell gas, leave the house and call your gas utility or 911. Gas lines and valves are only serviced by a qualified technician, and we keep the appliance isolated while work is done around it.
• NFPA 211 recommends an annual chimney inspection. A chase with visible siding damage is a good reason not to skip it this year.

Seattle & Puget Sound conditions

Puget Sound weather is hard on chimney chases in a specific way. Our rain is not heavy, it is constant, and it arrives sideways on the south and west faces for months at a time. A chase sticks up above the roofline with no overhang to shelter it, so a small flaw at the cover, the corner trim or the roof flashing feeds water behind the siding week after week. Cedar and composite siding that stays damp from October through May grows moss and algae, which hold even more moisture against the wood. Freeze-thaw nights in the foothills and the eastern suburbs pop paint and open joints. Closer to the water, in West Seattle, Tacoma and the island communities, salt air corrodes galvanized nails and flashing faster than inland, and rust streaks on the siding are often the first visible clue. Because of all this, we always re-side with a proper water-resistive barrier and kick-out flashing even if the original builder skipped them, and we recommend checking the chase each fall before the rain sets in.