The most expensive winter repair call usually isn't a broken furnace. It's water. A half-inch supply line that splits behind a wall can release 50 gallons or more per hour, and it often keeps going for hours before anyone notices. By the time the tenant sees a ceiling stain or comes home from a holiday trip, you may be looking at drywall replacement, flooring, mold remediation, an insurance deductible, and a unit nobody can live in for a few weeks. Most of that can be prevented with a few hundred dollars and one organized afternoon per property in October.

Below is the winterizing plan I'd give any small landlord. It's organized by system, with separate steps for occupied and vacant units, and it covers the tenant communication that actually makes the plan work.

Start With the Heat Source, Because Everything Depends on It

Every freeze-protection step assumes the building stays warm. If the furnace or boiler fails during a cold snap, insulation and heat tape only buy you hours. Get the heating system serviced in September or early October, before HVAC companies fill up with no-heat emergency calls and start charging after-hours rates.

  • Professional tune-up — Expect to pay $90–$200 per system. The tech should check the heat exchanger for cracks, test the flame sensor and igniter, check gas pressure, and confirm the condensate line drains on high-efficiency units. A frozen condensate line is one of the most common reasons a 95% furnace shuts down on a cold night.
  • Filter stock — Leave a 3- or 6-month supply of correctly sized filters at each unit and write the size on the furnace cabinet in permanent marker. A clogged filter can trip the high-limit switch and shut the furnace off.
  • Thermostat batteries — Replace them every fall. Dead batteries in a battery-powered thermostat can leave the unit with no heat call at all.
  • Carbon monoxide detectors — Test every detector and replace any older than its rated life, usually 7–10 years. Many states require working CO alarms in units with fuel-burning appliances, and winter is when they matter most.

For boilers, have the tech check the expansion tank, the pressure relief valve, and the low-water cutoff. For electric baseboard units, a quick walkthrough confirming every zone heats up is enough. Cold zones often point to a failed thermostat, and that's usually the room where pipes freeze.

Don't schedule the furnace tune-up for November. That's when heating contractors are busiest, and a problem found then is a problem you'll likely be fixing in December.

Find and Protect Every Vulnerable Pipe

Pipes freeze where cold air reaches them: exterior walls, crawl spaces, unheated garages, attics, under kitchen sinks on outside walls, and anywhere a sill plate has gaps. Walk each property with a flashlight and an infrared thermometer, which costs about $25. On a cold morning, any pipe surface reading below 40°F is a candidate for protection.

  1. Insulate exposed runs — Foam pipe sleeves cost $1–$3 per six-foot section. Cover every accessible supply line in crawl spaces, basements, and garages, and tape the seams.
  2. Seal air leaks near plumbing — Moving air does more damage than still cold air. Use canned foam on rim joist gaps, dryer vent penetrations, and holes where lines pass through exterior walls.
  3. Add heat cable where insulation isn't enough — Self-regulating heat cable, around $40–$80 for a typical run, is worth it on supply lines in crawl spaces that regularly drop below freezing. Plug it into a GFCI outlet and check the indicator light every fall.
  4. Close crawl space vents — If your crawl space has foundation vents, close or cover them for the winter. Reopen them in spring.
  5. Shut off and drain exterior hose bibs — Close the interior shutoff, open the outside spigot to drain it, disconnect hoses, and add a $3 foam faucet cover. Frost-free sillcocks still split if a hose stays attached and traps water.

Label the main water shutoff while you're there. Use a bright tag, and photograph its location for your files and the tenant's. If a pipe bursts, how fast someone closes that valve decides whether you're replacing one drywall panel or an entire floor. Check that the valve actually turns. Old gate valves often seize, and you want to find that out in October, not during a flood.

Handle the Building Envelope: Roof, Gutters, and Drafts

Ice dams and drafty units cause slower damage than burst pipes, but they're still expensive. Ice dams form when attic heat melts snow on the roof and the water refreezes at the cold eaves. The meltwater then backs up under the shingles and drips into the walls.

  • Clean gutters after the leaves drop — $100–$250 for a typical single-family house. Clogged gutters make ice dams worse and send meltwater toward the foundation.
  • Check attic insulation and bypasses — Look for gaps around recessed lights, bath fans, and the attic hatch. Weatherstripping and an insulated cover on the hatch run about $30 and noticeably cut heat loss.
  • Weatherstrip doors and windows — Replace worn door sweeps and compressed weatherstripping. Tenants who feel drafts are more likely to run space heaters, which raises fire risk and electrical load.
  • Inspect the roof from the ground — Use binoculars to check for missing shingles, lifted flashing around chimneys, and damaged vent boots. Fix small problems now, because roofers in snow country can be hard to book by December.

If an attic or insulation upgrade turns into a real project with several trades, bids, and a budget, treat it like one. TrestleBook is built for construction project tracking and job costing, so you can see whether that $4,000 air-sealing and blown-in insulation job came in on budget, instead of piecing it together from receipts in March.

Every dollar spent on air sealing helps three ways: lower heating bills, lower freeze risk, and fewer tenant complaints about cold rooms.

Write the Tenant's Part Into the Plan

You can't monitor an occupied unit around the clock, so the tenant is part of your freeze protection whether you plan for it or not. Most tenants have never been told what to do. A one-page winter notice sent in mid-October fixes that. Keep it short and specific:

  • Minimum thermostat setting — Ask that the heat stay at 55°F or higher at all times, including while they're traveling. Check your lease. Many leases already require tenants to maintain heat, and if yours doesn't, add that clause at the next renewal.
  • Cold-snap routine — When the forecast drops below 20°F, open cabinet doors under sinks on exterior walls and let the faucets most at risk drip a pencil-thin stream overnight.
  • Travel notice — Ask tenants to let you know if they'll be gone more than three days in winter, so you can arrange a check or confirm the heat is on.
  • Shutoff location — Include a photo of the main water shutoff and the steps to close it.
  • Who to call — One number for emergencies and a clear definition of what counts: no heat, active water leak, or a CO alarm.

Keep a record of when you sent the notice and how. If a pipe freezes because a tenant turned the heat off over Christmas, that documentation matters for both an insurance claim and any deposit deduction. KeyLoft lets you log tenant communications alongside each property and unit, so the notice, the date, and the delivery method are easy to find later without searching through texts.

Ready to put this into practice? Download KeyLoft for Free — it’s free and works offline.

Vacant Units Need a Different Plan

A vacant unit in winter is your highest-risk asset. Nobody is there to notice a failed furnace, and many insurance policies limit or exclude freeze damage if a property sits vacant past a set period, often 30 or 60 consecutive days, unless you've taken reasonable steps to maintain heat or shut off and drain the water. Read your policy's vacancy clause before the unit goes empty, not after.

You have two realistic options:

  1. Keep it heated and checked — Best for units you expect to re-rent within weeks. Set the heat to 55–60°F, open interior doors and sink cabinets, and schedule an in-person check at least weekly. Add a smart thermostat or a $30–$60 Wi-Fi temperature sensor that alerts your phone if the temperature drops below 45°F. Add $15–$25 water leak sensors under sinks, by the water heater, and near the washer hookup.
  2. Fully winterize — Best for units that will sit empty all season, like a property mid-renovation or a seasonal rental. Shut off the main, open every faucet starting at the top floor, drain the water heater, blow out the lines with compressed air at around 40–50 PSI, and pour plumbing antifreeze (RV-type, not automotive) into every trap and toilet bowl. A plumber typically charges $150–$350 for this, and about the same to de-winterize later.

Whichever option you pick, log each inspection with the date, interior temperature, and any issues. If you ever file a claim, a dated record showing weekly checks at 58°F is much easier to defend than “I stopped by now and then.”

A $50 Wi-Fi temperature sensor is the cheapest insurance you'll ever buy for a vacant unit. It turns a furnace failure from a $20,000 loss into a $300 service call.

Budget, Schedule, and Track It Like a Recurring System

Winterizing works best as the same checklist every year, not a scramble before the first hard freeze. For a typical single-family rental or duplex unit, a realistic annual budget looks like this:

  • HVAC tune-up — $90–$200
  • Gutter cleaning — $100–$250
  • Pipe insulation, foam, weatherstripping, faucet covers — $40–$120
  • Filters, batteries, detector replacements — $30–$80
  • Sensors (one-time, per unit) — $60–$150

That totals roughly $300–$800 per unit, and the one-time costs drop out after the first year. Compare that to a typical freeze-damage claim, which often runs $10,000–$25,000 before deductibles, rent loss, and the time spent managing restoration crews.

Use a fixed schedule: furnace service booked by mid-September, the property walkthrough and pipe insulation in early October, the tenant notice by October 15, and gutters cleaned after the leaves are down in mid-to-late November. Set up a recurring maintenance task for each property in KeyLoft, check items off as you finish them, and attach the receipts. Every winterizing expense is a deductible repair or maintenance cost, and having it recorded per property saves time at tax season.

If you do a lot of this work yourself, keep in mind your hours have real value. Landlords who also freelance or run a side business often track their time to see whether DIY actually beats hiring out. Stintly handles time tracking and small-business finance for self-employed people, which makes it easy to see that the six hours you spent crawling under three houses might have been better spent on billable work while a handyman handled it for $300.

When a Freeze Happens Anyway

Even good preparation has gaps. If a tenant reports no water from a faucet during a cold snap, assume a frozen pipe and act before it splits:

  • Keep the faucet open — Flowing water and released pressure help the ice melt and reduce the chance of a rupture.
  • Apply gentle heat — Use a hair dryer, space heater (kept a safe distance away), or warm towels on the suspected section. Never use an open flame or propane torch.
  • Know when to stop — If you can't find or reach the frozen section, call a plumber. If the pipe has already split, close the main shutoff first, then call.
  • Document immediately — Take photos, write down the time, and note the outdoor temperature and thermostat setting. Notify your insurer within the timeframe your policy requires.

After any freeze event, add the cause to next year's checklist. If the pipe under the kitchen sink froze, that wall needs air sealing or heat cable, and the tenant notice should call out that cabinet by name.

Winterizing isn't complicated. It's a set of small, cheap tasks that are easy to forget until the first hard freeze. Do them in the same order every fall, give your tenants clear instructions, treat vacant units as the high-risk properties they are, and keep a dated record of everything. The landlords who get through winter without a disaster usually aren't lucky. They started in October.