May Home Maintenance Checklist: Finish Exterior Season Strong

May finishes what spring started. Across most of the country, temperatures sit in the range where sealants, caulk, and paint actually cure, so this is the month to seal the deck, refresh exterior caulk, and touch up paint before summer heat and thunderstorms close the window. Round it out with the irrigation backflow test most water utilities require, a pest perimeter before mosquito and tick season peaks, and the last of your cooling prep. That's the whole month: about a dozen tasks, most of them outside.

If April went well, May carries roughly half its load. Our spring maintenance guide takes the wide view of the whole season; here we're only concerned with what May itself demands.

Seal the deck while the weather still cooperates

Start with the water test: splash a cup of water on the boards. If it beads, your sealant is holding and you're done for the year. If it soaks in, the wood is drinking rain, and May is the time to fix that, because most sealants want moderate temperatures and a day or two without rain to cure.

Clean the deck first, let it dry fully, then roll or brush on a water-repellent sealant or stain. Budget 3–6 hours and $40–100 in materials, or $300–800 for a pro to do it. The math is lopsided: sealing costs $100–300 all-in, while a rotted deck runs $5,000–15,000 to replace. Unsealed boards absorb water, then warp, split, and rot from the fasteners outward.

Most decks need this every two years. Hot-humid zones 1–2 cut that in half, because intense UV and humidity wreck sealant in a single season, and very-cold zones 7–8 arrive at the same annual schedule by a different route: freeze/thaw. In hot-dry areas like 2B and 3B the two-year interval holds, but the engine moves exterior-finish tasks up the priority list there, since the sun is relentless even when the calendar isn't. Our deck, siding, and exterior guide covers the full cleaning-and-sealing process.

Caulk, paint, and driveway cracks: the sealing trifecta

These three jobs share a theme, which is keeping water out of places it destroys slowly, and they share May's mild-weather requirement.

• Refresh the exterior caulk. If April's walk-around flagged failing joints, May's dry stretch is when you actually cut them out and re-gun them. Both silicone and polyurethane want a clean, dry joint and a few rain-free days to cure, which most of the country now has. Budget one to two hours and $10–30 for materials, or $150–400 to have a pro do the whole perimeter. The stakes are the same as last month: water in the wall cavity means hidden rot and mold, and leaky joints raise energy costs 10–20%. Homes in marine zone 4C (Seattle, Portland) should treat this as high priority, because fall rains will test every joint you skipped.
• Inspect the paint and touch up now. Walk the house looking for peeling, blistering, chalking, or fading, and hit problem spots before summer sun accelerates them. The inspection takes 30 minutes; touch-up supplies run $20–100, or $200–600 for a pro to handle trouble areas. Exposed wood rots fast, and on homes built before 1978, peeling paint can expose lead-based layers, which is a health hazard worth treating seriously. Wood siding typically needs a full repaint every 5–7 years in harsh climates, 7–10 in mild ones.
• Fill driveway cracks. Clean out and fill anything wider than a quarter inch in concrete or asphalt. One to two hours, $10–40 in filler, or $100–400 professionally. Water that gets into a crack expands it, freeze by freeze, until a $20 fix becomes a $2,000–5,000 resurfacing job. One caution for asphalt: sealcoat every 3–5 years at most, since over-sealcoating traps moisture and degrades the surface.

Get the irrigation system tested and legal

If you have an in-ground sprinkler system, most municipalities require an annual certified test of its backflow preventer, the device that keeps fertilizer- and pesticide-laced irrigation water from siphoning back into the drinking supply. This is not a DIY job; it takes a certified tester 15–30 minutes and costs $50–150. Keep the report, because many water utilities want proof on file, fine homeowners $100–500 for missing it, and can shut off service until you comply.

In zones 5–6, where systems were winterized until the last freeze passed, spring startup often lands in May anyway, so have the tester come once the system is charged. In zones 1–3, startup happened a month or two ago; if the test didn't happen with it, book it now.

No irrigation system? You still have backflow hardware. Check the anti-siphon valves on your outdoor faucets, the small caps that keep a hose lying in a puddle of pesticide from contaminating your drinking water. Ten minutes, $5–15 if a valve needs replacing.

Build the pest perimeter before summer

Mosquitoes need 7–10 days and a bottle cap of standing water to produce a new generation, so May's defenses pay off all summer. Three tasks, in order of effort:

1. Dump the standing water. Walk the yard and empty flower pot saucers, bird baths, old tires, tarps, wheelbarrows, and toys, and keep bird bath water refreshed weekly. Fifteen to twenty minutes, essentially free. One forgotten container can sustain a local mosquito population for months, and mosquitoes carry West Nile virus among other diseases. In zones 1–2 this is a year-round habit, and the engine treats pest tasks there as high priority.
2. Get the tick and flea rhythm going. The yard treatment runs every other month from April through October, so if April's round went down you're covered until June; if it didn't, start now. Target the shady, damp spots where ticks wait: under trees, along tall-grass borders, in leaf litter, and around the places pets like to rest, and keep the grass mowed short at the tree line. Figure 20–30 minutes and $15–40 doing it yourself, or $75–200 for a pro application. The diseases at stake here, Lyme and Rocky Mountain spotted fever, make this more than a comfort issue, and skipping the yard means your pets pick fleas right back up no matter what you apply to them indoors.
3. Cut shrubs back off the house. May growth closes gaps fast, and a hedge that had clearance in March can be brushing the siding by Memorial Day. Prune until 12–18 inches of open air separates plantings from the walls, and give the condenser 2–3 feet on every side. Plan on one to three hours DIY, or $75–250 if a landscaper handles it. Greenery pressed against the house holds dampness there and hands termites and carpenter ants a covered route inside; treating either infestation runs $2,000–5,000.

Last call on cooling prep

If April's AC tune-up never happened, May is the deadline, not the extension. The professional visit runs $100–200 for 2–3 hours of coil cleaning, refrigerant checks, and blower lubrication, and companies book solid the week of the first heat wave. Two quick DIY items either way:

• Flush the condensate drain line. Every hour the AC runs, the indoor coil pulls water out of the air and sends it down one narrow pipe, and algae grows happily in that pipe. A cup of vinegar or diluted bleach in the access tee now, before cooling season starts, means it never gets the chance to clog. Fifteen minutes and $5–15. Skip it and the failure arrives in August: water backing up into the ceiling, or a safety switch shutting the system down mid-heat-wave.
• Clean the outdoor condenser if you haven't: clear debris to 2 feet of clearance and rinse the fins gently with a hose. Twenty to thirty minutes, under $10. Blocked airflow can raise cooling costs 10–30% and shorten the compressor's life.

For the month-by-month picture of heating and cooling care, see our HVAC maintenance schedule.

If your home has the extras

One line each for the specialty systems. Pools open now in most climates, a 2–4 hour job or $200–500 professionally, and improper opening means algae bloom and shock treatments. Standby generators are due for an oil and filter change, 30–45 minutes and $15–40, because a seized engine reveals itself only during the outage. Septic systems should get a professional inspection and pump-out every three years or so ($300–600), which is cheap insurance against a $10,000–30,000 drain field replacement.

Common questions

Is May too late to seal a deck?

No, it's close to ideal in zones 3–6: warm enough to cure, usually before the humid stretch. In hot climates, work in the morning and check the label's temperature range, since most sealants won't cure properly on a sun-baked surface. The real mistake is waiting until fall and giving the wood a whole summer to bake unprotected.

Do I really need a certified backflow test, or can I check it myself?

If your municipality requires the test, it must come from a certified tester, and self-checks don't satisfy the requirement. The $50–150 fee is smaller than the $100–500 fines most utilities charge for a missed year. If you're not sure whether your area requires it, your water utility's website will say.

When does mosquito control actually need to start?

Before you're getting bitten. Breeding starts once nights stay mild, which for most of the country means April or May. Dumping standing water now prevents the July population rather than reacting to it. In zones 1–2, there is no off-season.

What if I never finished April's list?

Do April's water-management tasks first, gutters and grading, because standing water damages a house faster than dull sealant does. Then come back here and start with the deck and caulk while the weather holds.

May's task list looks different in Duluth than it does in Dallas, and a home with a pool, a well, and a cedar deck has a different month than a condo. SeasonKeep filters 220+ rules down to your home from your zip code, build year, and systems, free to start. Next up: the June checklist, where the focus shifts from finishing projects to surviving heat.