The snow-capped Front Range above a calm lake, with a line of bare trees and low rooftops along the far shore under a pale blue sky

Sweeping, inspection and repair for the chimneys of Thornton.

A planned Adams County city about ten miles north of the Colorado State Capitol, where homes date from the 1950s up to new construction.

Call (720) 964-2146Request a visit

Photo: David Herrera, CC BY 2.0

Six parts, cap to firebox, and how a Thornton winter works on each.

Pick a part to see what we look at, and what hard freezes, wet snow and dry air do to it north of Denver.

Begin on the roof
  1. An orange-brown brick chimney with a flat grey concrete top and a steel cap with black mesh, in front of a grey hip roof and a tan and brown wall
    From our Google Business Profile

    1Up on the roof

    Cap

    Snow, sun and hail meet the cap before anything else. Under its lid, a mesh holds embers in and keeps nesting animals out.

    We check: hail dents, mesh that has come loose, rust on the lid and its joins.

    Next: Crown
  2. A buff brick chimney with a crazed, cracked concrete crown, a black mesh cap on an orange collar and a rust-brown band at its foot, with a grey tarp on the roof below
    From our Google Business Profile

    2Right under the cap

    Crown

    Hairline cracks start here. At the Northglenn station, about 2.5 miles from the Thornton Civic Center, a normal January runs from a 19.0°F low to a 48.0°F high, so water that seeps into a seam at noon can be ice again by dawn.

    We check: hairline cracks, crumbling corners, a gap between slab and flue.

    Next: Flashing
  3. A buff brick chimney with a grey concrete top and a black mesh cap, a brown metal band at its foot, above a street of two-storey houses and autumn trees
    From our Google Business Profile

    3Where it meets the roof

    Flashing

    A metal collar, sealed with a bead of caulk, guards the spot where the stack passes through the roof. Wet snow slides off slowly, so one raised edge lets the melt run in behind the brick.

    We check: an edge that curls up, sealant that has cracked, rust streaks, a damp patch on a ceiling below.

    Next: Flue liner
  4. Two terracotta flue tile tops rising from a wide concrete crown with hairline cracks on a red brick chimney, above a fenced back yard and rooftops
    From our Google Business Profile

    4Behind the brickwork

    Flue liner

    Smoke and gas climb the liner where nobody sees them. The median Thornton home was built in 1997, which puts a typical flue near thirty years of use, and over a third of the city's homes are older than 1990.

    We check: a rusted or open seam, a cracked or shifted tile, a liner that does not suit the appliance.

    Next: Smoke chamber
  5. A soot-stained brick firebox with an orange cable running down its middle and a ribbed black vacuum hose at the right, under a dark steel lintel
    From our Google Business Profile

    5At the fireplace throat

    Smoke chamber and damper

    Just above the damper, the smoke shelf is where soot and creosote land first. A hearth lit on weekends fills slowly and a daily stove fast, but either one fills, and a damper left ajar sends heated room air up the flue all winter.

    We check: a glossy or tarry coat, a damper that shuts all the way, a shelf that crumbles or tilts.

    Next: Firebox
  6. A clean, empty firebox in a white marble hearth with a dark iron insert frame and an oak mantel above, a small floor grille below
    From our Google Business Profile

    6On the hearth floor

    Firebox

    Flames press against the firebox walls. Over the years the firebrick splits and the joints between bricks loosen, and a thin gap is far easier to close than one that has already let heat through to the wall behind.

    We check: mortar joints standing open, firebrick that cracks or flakes, a hearth that stays level and firm.

    See all six
1Cap2Crown3Flashing4Flue liner5Smoke chamber6FireboxAll six

What we look after, roof to fireplace.

  1. A sooty firebox under a decorative metal frame, with a cleared floor and a white ash grate, an orange rod laid across it and a black mesh curtain at the left
    From our Google Business Profile

    Soot clings to the flue walls and the smoke shelf. Brushes loosen it, then the firebox is cleared out. A clean flue draws well and gives a spark nothing to hold.

    • Flue from damper to cap
    • The smoke shelf and firebox floor
    • What we found, in plain words
    Sweeping in detail
    Schedule a sweep
  2. A white-painted brick chimney seen from above, with a blue steel cap and two pale clay flue tops on a concrete crown, among ponderosa pines and autumn leaves
    From our Google Business Profile

    Each part from cap to firebox gets a careful look: yearly, after a storm or chimney fire, and again at a sale, which NFPA 211 treats as a Level 2 occasion.

    • Cap, crown and flashing
    • The flue over its whole length
    • Each fault named plainly
    Inspection in detail
    Request an inspection
  3. A white-painted brick chimney with a crumbling crown, loose pieces of mortar and a steel cap, above a patio with blue-cushioned chairs and pine trees
    From our Google Business Profile

    Mortar, firebrick, caps, crowns and flashing are what we mend. Fixing a small fault in autumn is a lighter job than meeting the same fault after a winter of hard freezes.

    • Crown repair or rebuilding
    • Replacement caps and screens
    • Flashing and joint repointing
    Repairs in detail
    Request a repair
  4. A soot-stained brick firebox with an orange cable running down its middle and a ribbed black vacuum hose at the right, under a dark steel lintel
    From our Google Business Profile

    Cleaning suits fireplaces and stoves that are lit only occasionally: the firebox and shelf cleared of ash and soot, the pipe brushed and the damper opened and closed completely.

    • Firebox and shelf cleared
    • Stove, insert and pipe
    • Damper worked fully
    Stove and hearth cleaning
    Request a cleaning

What the Thornton sky does to a chimney.

Three things the weather brings to this side of the Front Range, and why a small fault is easier to fix early.

  1. 01 / 03

    148.6. Days a year with a freezing low, nearly five months of them

    At the Northglenn station, about 2.5 miles from Thornton's Civic Center, the 1991 to 2020 normal low is 32°F or lower on 148.6 days a year and on 28.8 days in January, when the average day runs from 19.0°F to 48.0°F. Melt water that slips into a crack in the afternoon can be ice by dawn, again and again. Weight counts too: for the storm of November 5 to 9, 2024, NWS Boulder lists 12.8 inches at Thornton 1.1 SW and 9.7 inches at Thornton 2.1 N, in snow its summary calls very heavy and wet.

    Source: NOAA U.S. Climate Normals 1991 to 2020, Northglenn station; NWS Boulder, November 5 to 9, 2024 snowfall reports

    Photo: Michael Rieger (FEMA), Public domain

    Photo: Michael Rieger (FEMA), Public domain

  2. 02 / 03

    80 mph. Gusts of 60 to 80 mph were common, and a city lost power

    NWS Boulder's summary of the April 6 to 7, 2024 windstorm puts the strongest winds on the plains along and north of a line from Denver to Fort Morgan, with gusts of 60 to 80 mph common, and says up to 150,000 customers lost power at the peak, most of them around Denver. Thornton sits just north of that city. Wind finds the cap and the crown first, so after a blow we look for loose mesh, lifted lids and cracked seams.

    Source: NWS Boulder, April 6 to 7, 2024 windstorm summary

    Photo: Paul Dineen, CC BY 3.0

    Photo: Paul Dineen, CC BY 3.0

  3. 03 / 03

    0.45 in. January, the driest month

    At the Northglenn station the driest month of the 1991 to 2020 normals is January, with 0.45 inch, while December and February bring 0.48 and 0.54. The whole year adds up to 14.51 inches of precipitation. Grass and old shingles dry out fast in air like that, so a spark that escapes the flue has plenty to land on. That is why the mesh of a cap matters: the model residential code allows openings of 1/2 inch at most.

    Source: NOAA U.S. Climate Normals 1991 to 2020, Northglenn station; IRC R1003.9.2

    Photo: Louis, CC BY-SA 2.0

    Photo: Louis, CC BY-SA 2.0

Chimneys up close.

Nine photos from our Google Business Profile.

Tap a tag to jump to that part of the walkthrough above.

Thornton, from Original Thornton to North Creek Farms.

We are based in Thornton, a home rule city of Adams County about ten miles north of the Colorado State Capitol. It began in 1953 as farmland off Washington Street, the first fully planned community in the county, and was incorporated in 1956. The map below draws the present city limits and a handful of named spots within them: in the south, in the southwest, just north of both, in the southeast, south of the middle, just north of it, farther north and at the northern edge.

Unsure whether your street falls inside our area? Call (720) 964-2146 and we will tell you.

City of ThorntonContour lines every 100 ft

Terrain: AWS Terrain Tiles. City boundary: U.S. Census Bureau TIGERweb. Names and positions of places: OpenStreetMap contributors.

  • Thornton
  • Original Thornton
  • Civic Center Park
  • Lambertson Lakes
  • Spratt Lake
  • Carpenter Park
  • Eastlake
  • Hunters Glen Lake
  • North Creek Farms Park
A white-painted timber grain elevator with green trim and rust-red roofs beside a gravel lot, under a clear blue sky

Photo: Jeffrey Beall, CC BY-SA 3.0

Thornton homeowners ask.

Short answers; a figure always comes with its source.

How often does a chimney need sweeping?

It depends on how you burn, not on the calendar. NFPA 211 advises an annual inspection, and the findings of that visit tell you whether a sweep is due. Census Bureau estimates for 2020 to 2024 put 35,207 of Thornton's 50,566 occupied homes on utility gas and just 13 on wood (margin of error 21), so most fireplaces here serve a cold evening now and then.

Source: NFPA 211; U.S. Census Bureau, American Community Survey 5-year data, 2020 to 2024

Is an inspection wise when buying or selling a house?

Yes. NFPA 211 calls for a Level 2 on a sale or transfer, which adds a look at the attic and crawl space and a video check of the flue to the usual Level 1 inspection. In Thornton the Census Bureau counts 2,261 of the city's 52,250 homes as built in the 1950s and 13,665 in the 2000s, the largest decade, so one block can hold very different chimneys.

Source: NFPA 211; U.S. Census Bureau, American Community Survey 5-year data, 2020 to 2024

Why does the fireplace smell worse in humid or warm weather?

Soot and creosote hold odor. In muggy or warm air the flue pulls weakly, and a draft that runs backward can carry the smell into the room. Cleaning out the deposit removes the source, and keeping the damper shut helps hold back what remains.

What does a chimney crown do?

It is the slab on top of a masonry chimney, and it sheds water off the brick and the flue. Where the January normal is a 19.0°F low and a 48.0°F high, as at the Northglenn station, water that gets into a crack can freeze overnight and push it wider.

Source: NOAA U.S. Climate Normals 1991 to 2020, Northglenn station

Is a cap really necessary?

Almost always. Besides blocking rain, snow, birds and animals, the cap's mesh stops sparks from escaping, and under the model code (IRC R1003.9.2) its openings may be no wider than 1/2 inch. Whether Thornton applies other rules is a question for the city, which can confirm the codes it has adopted.

Source: International Residential Code, section R1003.9.2

Do you serve my part of Thornton?

We are based in Thornton. Not sure your address is inside our area, whether you live around Eastlake, in Original Thornton or somewhere else? Phone (720) 964-2146 and we will tell you.

How do I set up a visit?

Call (720) 964-2146 (Sunday to Saturday, 7 AM until 9 PM). The form further down accepts a request at any hour, and a person rings you back to agree a time.

Set up your chimney visit.

Use the form to say what looks wrong, or simply phone. A person rings you back to pick a day.

  1. 1Reach out Call the office, or send a few lines on the form.
  2. 2A person rings back Someone phones to find a day that suits you.
  3. 3Cap to firebox The visit works down the chimney in order, the roofline first and the hearth last.
  4. 4Your call We say what we found, and you decide what comes next.

By phone

Sunday to Saturday, 7 AM until 9 PM

(720) 964-2146

By form

Any hour, day or night

Photo: Hail Storm Park And Streets I, Eric Johnson, CC BY-SA 3.0

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Rather talk it through? Call (720) 964-2146, Sunday to Saturday, 7 AM until 9 PM.

Planning a fire before the first hard freeze, or puzzled by something up on the roof? Ask us.

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