Getting Your Fireplace Ready for a Longmont Winter

Start in September and aim to finish before October is half over. That is when freezing nights stop being rare here, and it leaves time for a sweep, an inspection and any small repair before you actually want a fire on the grate.

Why the calendar matters more than the first cold snap

NOAA's 1991 to 2020 normals for its Longmont 2 ESE station show how quickly the season turns. September averages only 1.6 nights at or below 32°F. October jumps to 15.2, with a normal low of 32.9°F, and November reaches 26.9. By December, freezing nights are the rule: on average 30.5 of its 31 nights.

That curve has two practical effects. First, mortar and crown repairs need mild weather to cure properly, so anything found in late fall may have to wait for spring. Second, everyone wants a sweep in the same few weeks. Booking while September nights are still warm keeps your options open.

Two short checklists: outside, then inside

Outside, before the first fire

You do not need to climb onto the roof to do most of this. A pair of binoculars and a walk around the house will cover it.

• The cap. Is it still sitting square on the flue, with the mesh intact? Summer hail and wind can dent a lid or pull a screen loose.
• The crown and upper bricks. Look for chunks missing from the edge of the slab, white staining, or bricks with flaking faces.
• The flashing. Check where the chimney meets the roof for metal that has lifted or sealant that has pulled away.
• Branches. Trim anything that hangs within reach of the chimney top. Leaves clog caps and branches give squirrels a ladder.
• The woodpile. Stack it off the ground, cover the top only, and keep it away from the house walls.

Inside: the fireplace, the stove and the room

1. Clear last season's ash and look at the firebrick. Cracks wider than a hairline, or mortar falling out between bricks, deserve a professional look.
2. Open and close the damper several times. It should move freely and seal when shut.
3. On a stove, check the door gasket. Close the door on a strip of paper: if it slides out easily, the seal is tired.
4. Test smoke and carbon monoxide alarms, and put fresh batteries in any that need them.
5. Move rugs, baskets and furniture back from the hearth, and set out a metal ash bucket with a lid.
6. If you burn gas logs, make sure the glass and the logs are in their proper positions and the vent outside is clear.

If the fireplace has sat unused for a few years, or you have just moved in, treat this season differently: have the chimney inspected before any fire at all. You cannot know what the last owner burned, or what moved in while it sat cold.

Dry air and stray sparks

Winter in this part of the Front Range is dry as well as cold. December is the driest month on the same NOAA record, with a normal of 0.46 inch of precipitation, and January and February add only a little more. Grass, mulch and old shingles can stay tinder dry for weeks at a time. That is one reason the cap matters. Its screen doubles as the spark arrestor, and under the model residential code no opening in that screen should be wider than half an inch, although the rules that bind a given house are whichever ones the city has adopted.

The same dryness affects ash. Coals dumped into a plastic bin or onto a flower bed in a dry December can smolder long after you have forgotten them. A covered metal bucket, set on concrete and away from the house, removes the risk.

The first fire of the year

Make it small. Light a few pieces of dry kindling with the damper fully open and watch how the smoke behaves. It should rise straight up the flue within a minute or two. If it rolls out into the room, if you smell something sharp or musty, or if the chimney makes noises you have not heard before, put the fire out and have the chimney looked at before using it again. A clogged cap, a nest built over the summer or a damper that has not opened all the way are the usual causes, and our guide to nests and blockages covers the signs.