When Does a Renton Chimney Need Relining? Findings, Liner Types and Timing

A masonry chimney is a brick shell built around a flue. In most houses that flue is a stack of clay tiles, each roughly two feet tall, set one on the next with a mortar joint between them. The tiles have three jobs. They hold the heat of the fire away from the brick and from the wood framing the chimney passes on its way up. They keep smoke, water vapor and the acids in exhaust out of the mortar. And they give the gases a smooth passage of a known size, which is what lets the chimney draw.

When a tile cracks or a joint washes out, all three jobs fail at that spot. Heat reaches brick that was never meant to face it, exhaust seeps into the shell, and the draft weakens.

Nearly every reline starts with one of the findings in the table. None can be confirmed by looking up from the hearth with a flashlight, which is why the decision rests on a recorded scan of the whole flue.

One hairline crack in one tile does not put a chimney in the same category as a flue with missing joints from top to bottom. The scan shows where each defect sits and how many there are. The quote follows from that.

Liners fail with age, with water and with movement, and Renton's housing gives all three time to work. Census estimates for 2020 to 2024 place the median Renton home in 1988, but that middle figure hides a large older stock: about 39 percent of the city's 42,551 housing units went up before 1980 and about 14.5 percent before 1960. Counted by decade, some 15,310 units date from the 1940s through the 1970s, more than a third of the city. The medians in Newcastle, Snoqualmie and Maple Valley are 1999, 2005 and 2001.

Then there is the ground. In 2001 the Nisqually earthquake, a magnitude 6.8 event, shook Renton hard enough that the city's hazard annex still lists the result: "primarily cracked masonry and collapsed chimneys". U.S. Geological Survey teams who went through the wider region afterward, one block at a time, examined roughly 60,000 chimneys and found 1,556 damaged. A stack that stayed upright that morning may still carry a broken tile inside a shell that looks intact from the yard. Nor is the risk behind us: over the coming 50 years, the state Department of Natural Resources estimates at 85 percent the odds of a deep earthquake reaching at least magnitude 6.5 somewhere under the Puget Sound region.

Water is the third factor. The same annex counts 154 days with precipitation in an average Renton year. A flue with no cap, or with a cracked crown above it, takes that water straight down the tiles, and wet mortar joints erode faster than dry ones.

Stainless steel. A continuous metal tube, rigid for a straight flue and flexible for one with offsets, is lowered from the top and joined at the bottom to the fireplace throat, the insert or the stove. Insulation goes around it where the appliance calls for it. Most wood-burning relines we do use this method, because it works in a flue whose tiles are past saving and it can be sized exactly to the appliance.

Cast-in-place. A cement-like mix is formed against the inside of the old flue, which produces a new seamless wall and also stiffens a tired chimney. It suits some older structures and takes more labor.

Aluminum. Light-gauge aluminum liners exist for certain gas appliances only. They are never used with wood.

New clay tiles. Breaking out the damaged tiles and setting new ones is possible when a short section has failed and the flue runs straight. In a tall or offset chimney it is rarely the practical choice.

Which of the four fits depends on the fuel, the appliance, the height and the route the flue takes.

Plenty of homes with a Renton mailing address are not in the city. Fairwood is the best-known case: King County lists it as urban unincorporated land, since voters there turned down annexation to Renton in November 2010, and county rules apply. For unincorporated addresses the county's permitting handout says a residential mechanical permit is needed whenever a wood stove or a fireplace is installed, replaced or moved; the application is filed online at MyBuildingPermit.com. Gas log inserts are on the exempt list for single-family houses, although its gas piping can call for a separate permit. When a reline goes with a new stove or insert, we confirm which office has jurisdiction over your address before the quote is written.

Relining with us starts at $1,900. A tall chimney, a flue with offsets, an insulated liner or a second flue in the same stack moves the figure upward, and the top of our range is $5,900. For context only: Fixr's guide gives $1,800 to $4,000 for liner installation nationally. That is a countrywide span, not a Renton quote and not ours.

Every reline begins with the inspection visit, billed $99 plus tax per chimney, camera scan included when the flue calls for one. Once you sign off on the reline, that $99 is taken off what the work comes to.