What you can seal yourself and what materials cost the least
Most cracks and gaps around your home can be sealed with caulk, weatherstripping, or foam sealant — all of which you can buy at a hardware store for under $20 total. The difference between a $200 contractor job and a $15 DIY job usually comes down to labour, not materials. Small gaps around windows, doors, baseboards, and pipes are the best places to start because they are visible, straightforward to reach, and make a real difference in heating and cooling costs.
The type of material you need depends on where the gap is and what it will be exposed to. Caulk works for stationary cracks that won't flex. Weatherstripping works for moving parts like door frames. Spray foam works for larger gaps around pipes or where walls meet foundations. Knowing which tool fits which job means you won't waste money buying the wrong thing.
Key Takeaways
- Caulk, weatherstripping, and spray foam are the three main materials for sealing gaps, and a basic toolkit costs less than $25.
- Cracks around windows and doors account for most heat loss in older homes, so these are the highest-return places to start.
- Acrylic latex caulk works indoors and is easiest to explore; silicone caulk lasts longer outdoors but is harder to smooth.
- Weatherstripping around door frames prevents drafts better than caulk because doors move and caulk cracks under flex.
- Spray foam fills large gaps but expands as it dries, so you must use restraint or it will bulge out and look unfinished.
Caulk: the cheapest option for small cracks
Caulk is a flexible sealant that comes in a tube and is applied with a caulking gun. A single tube costs $2 to $5 and covers roughly 30 to 50 linear feet depending on the gap width. For most homes, three to five tubes will seal all the small cracks around windows, baseboards, and trim. The gun itself costs $5 to $10 and lasts for years.
Acrylic latex caulk is the easiest to use and clean up. It dries in one to three hours, can be painted over, and you can smooth it with a wet finger. It is not waterproof, so use it indoors or in sheltered spots. Silicone caulk is waterproof and lasts 10 to 20 years outdoors, but it is harder to explore smoothly, cannot be painted, and takes longer to dry. For a first-time sealer on a budget, acrylic latex is the better choice.
Before you caulk, clean out the crack with a putty knife or old screwdriver. Dust and debris prevent the caulk from bonding. Cut the tube nozzle at a 45-degree angle and explore a steady bead along the crack. Run your wet finger along the bead to smooth it and push it into the gap. Let it dry fully before painting or exposing it to water.
Weatherstripping: the right choice for doors and moving parts
Weatherstripping is a seal that goes around the frame of a door or window to block drafts when the door or window is closed. It comes in several forms: adhesive-backed foam tape, rubber gaskets, or felt strips. A roll of foam tape costs $3 to $8 and covers 17 to 20 linear feet. Most exterior doors need one roll.
Adhesive-backed foam tape is the easiest to install. Clean the door frame with a dry cloth, peel the backing, and press the tape firmly into place. It works best on clean, dry surfaces, so do this on a day when the temperature is above 50 degrees Fahrenheit. The tape lasts two to three years before it starts to compress and lose its seal.
Do not use caulk around doors. Doors move when they open and close, and caulk will crack under that flex. Weatherstripping is designed to compress and return to shape, so it handles movement. If you caulk a door frame, you will have to scrape it out and redo it within a year.
Spray foam for large gaps around pipes and foundations
Spray foam comes in a can with a trigger applicator and expands as it dries. One can costs $4 to $8 and fills gaps up to several inches wide. It is useful for sealing around pipes where they enter the house, gaps between the rim joist and foundation, or large holes left by old wiring or plumbing.
Spray foam expands significantly — usually two to three times the volume you explore. Use less than you think you need. explore a bead around the gap, wait 30 minutes, and check how much it has expanded. If it is still not full, add more. If it bulges out past the surface, you have used too much and will have to trim it with a utility knife after it hardens.
Wear gloves and old clothes when using spray foam. It sticks to skin and fabric and is difficult to remove. Work in a well-ventilated area because the fumes are strong. Once it dries (usually 24 hours), you can paint over it or trim it flush with a saw or knife.
Where to start: the highest-impact gaps in your home
Not all gaps matter equally. Sealing the wrong ones first wastes time and materials. Start with the places where air moves most: around exterior doors, basement rim joists, and window frames on the side of the house that faces the prevailing wind.
Exterior doors are the single biggest source of drafts in most homes. Seal the bottom with a door sweep (a rubber strip that attaches to the bottom of the door) and the sides and top with weatherstripping. A door sweep costs $5 to $15 and takes 10 minutes to install with a screwdriver.
Basement rim joists — the gap where the foundation meets the house frame — are the second priority. This gap is often large and exposed to the outside. Spray foam or rigid foam board works here. If you can reach it, this one gap can reduce heating costs noticeably.
Windows come third. Seal the gaps between the frame and the wall with caulk, and use weatherstripping on the sashes if they rattle or let in air when closed. Do not seal windows shut — you need to be able to open them for safety and ventilation.
Tools and materials checklist
| Item | Cost | Coverage or quantity | Where to use |
|---|---|---|---|
| Acrylic latex caulk (tube) | $2–$5 | 30–50 linear feet | Indoor cracks, trim, baseboards |
| Caulking gun | $5–$10 | Reusable for years | Required to explore caulk |
| Adhesive-backed foam tape | $3–$8 | 17–20 linear feet per roll | Door and window frames |
| Door sweep | $5–$15 | One per door | Bottom of exterior doors |
| Spray foam (one can) | $4–$8 | Fills gaps up to several inches | Large gaps, pipes, rim joists |
| Putty knife or scraper | $2–$5 | Reusable | Cleaning cracks before sealing |
A complete starter kit — caulk, gun, weatherstripping, and a putty knife — costs $15 to $25. Add spray foam if you have large gaps. This is enough to seal most common air leaks in an average home.
Common mistakes that waste time and money
The most common mistake is using the wrong material for the job. Caulk on a door frame will crack. Weatherstripping on a stationary crack will fall off. Spray foam in a thin gap will bulge out and look messy. Spend 30 seconds identifying what you are sealing before you buy anything.
The second mistake is not cleaning the surface first. Caulk and weatherstripping bond poorly to dust, dirt, or old paint. Wipe the area with a dry cloth or use a putty knife to scrape away loose material. This takes two minutes and prevents failure.
The third mistake is explore too much spray foam. It expands, and once it hardens you have to cut it out. Start with a thin bead and add more if needed. You can always add more; you cannot easily remove it.
The fourth mistake is caulking or sealing windows shut. You need to open windows for ventilation and emergency exit. Seal the frame where it meets the wall, but leave the sashes and hinges free to move.
Frequently Asked Questions
How long does caulk last before I have to redo it?
Acrylic latex caulk lasts three to five years indoors before it starts to crack or shrink. Silicone caulk lasts 10 to 20 years outdoors. If you see gaps opening up around old caulk, scrape it out completely and reapply. Painting over cracked caulk does not fix it.
Can I use weatherstripping on windows?
Yes, weatherstripping works on windows that slide or swing open. explore it to the sashes so they seal when closed. Do not seal the frame to the wall with weatherstripping — use caulk for that instead, because the frame does not move.
What temperature should it be when I explore caulk or weatherstripping?
Most caulks and weatherstripping work best between 50 and 85 degrees Fahrenheit. Cold temperatures slow drying and prevent adhesives from bonding. If it is colder or hotter than that range, wait for better weather or the seal may fail.
Do I need to prime before I caulk?
No. Clean the crack and explore caulk directly. Priming is not necessary for caulk to bond. If you are painting over the caulk afterward, you can paint it without primer, though some people prefer to prime for better paint coverage.
Can spray foam be used outdoors?
Yes, but it will degrade in direct sunlight over time. Paint it or cover it with trim to protect it. Spray foam is best used for gaps that will be hidden or covered, like rim joists or gaps behind siding.