Chase Covers and Factory-Built Chimney Repair

Drive through Lakeville, Blaine, Woodbury or Maple Grove and look at the chimneys. Most aren't brick. They're boxes framed from lumber and covered in the same siding as the house, with a metal flue inside and a sheet-metal lid on top. The American Community Survey puts the median year built at 1999 in Lakeville, 1997 in Woodbury, 1996 in Blaine and 1991 in Maple Grove, and in each of those cities between a third and nearly half of homes went up after 2000. That's factory-built fireplace country.

The weak point is the lid, called the chase cover. Builders usually put on a flat galvanized panel. Snow piles on it, meltwater pools in the middle, and after enough winters the panel rusts through or sags, and water runs down the flue pipe into the chase framing and the firebox below. Replacing it with a sloped cover that sheds water is one of the cheapest repairs that keeps a factory-built chimney going.

Signs you need this

• Rust stains running down the siding of the chimney box
• A dished or sagging lid that holds a puddle after rain
• Water dripping into the firebox or onto the glass of a gas fireplace
• Swollen or loose siding at the top of the chase
• A rusty cap or storm collar on the flue pipe

How we do it

1. Inspect from the roof, freeWe photograph the old cover, the storm collar, the flue cap and the top of the framing, and measure the chase.
2. Build to your chaseThe new cover is made to fit, sloped or cross-broken to run water off, with a skirt that laps over the siding and a drip edge.
3. Swap the coverThe old panel comes off, rotten wood is shown to you before it is covered, and the new cover goes on with the flue collar sealed.
4. Reset the flue topThe storm collar and the cap listed for your chimney go back on, or get replaced if they're rusted.

Why the suburbs see so many rusted chase covers

Factory-built chimneys came into wide use in the same decades the outer suburbs were built, and most of those houses are now 25 to 35 years old. That's about the age when a thin galvanized cover gives out in our climate. NOAA's 1991–2020 normals put MSP at 51.2 inches of snow a year with about 90 days of an inch or more on the ground, and a flat lid on a chase holds that snow until it melts. Every warm afternoon puts water on the panel; every cold night freezes what's left.

Gas fireplaces are common in these homes. Natural gas heats 85.8% of homes in Lakeville, 88.1% in Blaine and 85.6% in Maple Grove (ACS 2024), and many factory-built fireplaces from those years burn gas. A wet chase can rust the vent pipe and damage the unit's controls, which turns a few-hundred-dollar cover into a much larger fireplace repair.

What a good chase cover has

A replacement cover is sized to your chase and shaped to shed water rather than hold it.

• A slope or cross-break so no water stands on top
• A skirt that laps down over the siding, not tucked under it
• A hemmed drip edge so water drips clear of the siding
• A raised collar around the flue opening, sealed to the pipe
• Heavier metal than the original builder-grade panel

Factory-built chimney parts and what they cost

A factory-built fireplace and chimney is a tested and listed system, and its flue sections, storm collar and cap should be the parts listed for that model. St. Paul, for example, treats factory-built fireplaces as mechanical-permit work and describes them as AGA- or UL-approved units. When a part has rusted or is the wrong one, we replace it with a listed part. National 2026 cost guides put a chase cover at $300 to $700 and factory-built chimney repairs at $250 to $1,200. Rotted framing or siding is noted with photos and priced separately.