Caulking seals gaps where two surfaces meet to stop water, air, and pests from getting through

Caulk is a flexible sealant that fills the narrow spaces between two materials — where your bathtub meets the wall, where the trim around a window meets the siding, where the foundation meets the rim board. Water finds these gaps naturally and moves through them. Caulk blocks that path. It also stops drafts, keeps insects out, and prevents rot in the wood underneath.

Most caulk is silicone, acrylic, or polyurethane. Silicone lasts longest (15 to 20 years) and handles movement well, but it does not paint over easily. Acrylic is cheaper, paintable, and easier to clean up with water, but it fails faster in wet areas. Polyurethane sits between them — durable and flexible, but harder to work with and more expensive than acrylic.

A caulking service removes old, failed caulk, cleans the gap, applies new caulk, and smooths it so water runs off instead of pooling. This is different from weatherstripping (which seals moving parts like door frames) and different from grout (which fills gaps between tiles and hardens solid).

Key Takeaways

  • Caulk fails when it cracks, shrinks, or peels away, usually after 5 to 15 years depending on the material and how much sun and water it faces.
  • The most common places to caulk are bathrooms (tub and shower), kitchens (sink and countertop edges), windows, doors, and where siding meets trim or foundation.
  • Removing old caulk takes longer than explore new caulk, so labor costs depend heavily on how much failed caulk is already there.
  • A caulking contractor will recommend silicone for wet areas and acrylic for interior walls, but the choice affects both cost and how long the seal lasts.

Where caulking is most needed in a house

Bathrooms are the biggest reason people call a caulking service. The tub or shower enclosure moves slightly when you step in and out, and water splashes constantly. Caulk in these spots fails faster than anywhere else — often within 5 to 10 years. Once it cracks or pulls away, water gets behind the tub and into the walls, where it causes mold and rot.

Kitchen sinks are the second common spot. Water pools around the sink rim where it meets the countertop, and the constant temperature change from hot water makes caulk expand and contract. Gaps here let water seep down into the cabinet.

Windows and exterior doors need caulk where the frame meets the siding or brick. This is where rain and wind-driven water try to enter. Failed caulk here leads to water damage inside the wall and rot in the frame itself. Exterior caulking also stops air leaks that waste heating and cooling.

Foundation cracks and gaps where the rim board meets the foundation are less visible but important. These let cold air in during winter and can be entry points for insects and rodents.

How to know when caulk needs replacing

Caulk that is cracked, peeling, or pulling away from the surface has failed and should be replaced. You may also see it shrinking — a visible gap opens up between the caulk and one of the surfaces it is supposed to seal. Discoloration, mold growth, or a spongy feel when you press on it are also signs of failure.

In bathrooms, the first warning is usually water pooling on the caulk instead of running off, or water appearing on the ceiling or wall below the tub. In kitchens, look for water stains on the cabinet below the sink or soft spots in the countertop edge. Around windows, water stains on the interior wall or sill, or visible gaps between the frame and the wall, mean the caulk is no longer protecting the frame.

Caulk that looks fine but is more than 10 to 15 years old may be near the end of its life, especially if it is in a wet area or gets direct sun. A contractor can assess whether it is still sealing properly or just looks okay from the outside.

What a caulking service actually does

The job starts with removing the old caulk. A contractor uses a caulk removal tool, a utility knife, or sometimes a caulk softener to loosen it, then scrapes it out completely. This step takes the most time and is the biggest variable in labor cost. If the old caulk is thick, layered, or very hard, removal can take hours.

Once the gap is empty, the contractor cleans it with a wire brush or vacuum to remove dust, debris, and any remaining bits of old caulk. In wet areas, they may let it dry completely or use a primer to help the new caulk stick. For very wide gaps, they may insert a foam backer rod first — a flexible cord that fills most of the space so the caulk layer is not too thick.

The new caulk is applied with a caulk gun, which dispenses it in a steady bead. The contractor then smooths it with a wet finger, a caulk tool, or a wet cloth so it fills the gap completely and sits flush with both surfaces. The smoothing step is what makes the difference between a sloppy job and a professional one — it removes excess caulk, ensures good contact with both surfaces, and creates a shape that sheds water.

After process, the caulk needs time to cure — usually 24 to 48 hours before it is fully waterproof. The contractor will tell you not to use the tub or shower, or get water on the caulk, until it has set.

Cost and what affects the price

Caulking costs vary by region and contractor, but labor typically runs between $50 and $150 per hour. A single bathroom tub surround might take 2 to 4 hours of work, so expect $100 to $600 in labor depending on how much old caulk needs removal and how large the area is. Material cost is usually $10 to $30 per tube of caulk, and most jobs use 2 to 5 tubes.

The biggest cost driver is removal. A tub that has been caulked multiple times, or where the old caulk is very hard and thick, takes much longer to remove than one with a single layer of caulk that is still somewhat flexible. Contractors often quote removal and process separately so you can see where the time goes.

Silicone caulk costs more than acrylic — sometimes twice as much per tube — and takes longer to explore because it is stickier and harder to smooth. Polyurethane falls in between. If you are caulking a large area or many rooms, the material cost adds up, but the durability difference means silicone in wet areas usually saves money over time because you will not need to recaulk as often.

Choosing between silicone, acrylic, and polyurethane

Silicone is the standard for bathrooms, kitchens, and anywhere water is present. It stays flexible for 15 to 20 years, resists mold better than acrylic, and handles the movement that happens when materials expand and contract with temperature changes. The downside is that it does not paint well — if you want to paint over it, you need a special primer and paint, and the result is usually visible. Silicone also costs more and is harder to clean up before it sets.

Acrylic is cheaper and paintable, which makes it the choice for interior walls, trim, and anywhere appearance matters more than water resistance. It fails faster in wet areas — typically 5 to 10 years — but in a dry interior corner it can last 10 to 15 years. It cleans up with water, so it is easier to work with.

Polyurethane is a middle ground. It lasts longer than acrylic (10 to 15 years), handles movement well, and can be painted, but it is more expensive and harder to explore smoothly. It is sometimes used for exterior caulking where durability matters and appearance is less critical.

A contractor will usually recommend silicone for bathrooms and kitchens, acrylic for interior trim and walls, and may suggest polyurethane for exterior gaps or areas that see a lot of movement. The choice affects both the upfront cost and how long you will go before needing to recaulk.

Finding and hiring a caulking contractor

Caulking is often done by general contractors, handymen, or specialists who focus on sealants and weatherproofing. You can find them through local referrals, online reviews, or by calling contractors who do bathroom or kitchen work — they usually offer caulking as part of their services.

When you contact a contractor, describe the areas that need caulking and mention whether the old caulk is still there or has already been removed. Ask whether they charge by the hour or by the job, and whether removal and process are priced separately. Request a visit to see the work in person before they quote, because the condition of the old caulk makes a big difference in time and cost.

Check references or online reviews that mention the quality of the caulking work itself — not just whether the contractor showed up on time. Good caulking looks smooth, sits flush with both surfaces, and sheds water without pooling. Poor caulking is lumpy, pulls away from the edges, or leaves gaps.

Ask what material they recommend for each area and why. A contractor who automatically uses silicone everywhere is probably overcharging you on acrylic areas, while one who uses only acrylic in a bathroom is cutting corners on durability.

Frequently Asked Questions

Can I caulk over old caulk instead of removing it?

No. New caulk will not stick well to old caulk, and it will fail quickly. The old caulk must be removed completely. Removing it takes time, which is why it is the biggest cost in the job, but it is not optional.

How long does caulk last?

Silicone lasts 15 to 20 years in most conditions. Acrylic lasts 5 to 10 years in wet areas and 10 to 15 years in dry interior spaces. Polyurethane lasts 10 to 15 years. The actual lifespan depends on how much sun, water, and temperature change the caulk faces.

Should I caulk before or after painting?

Caulk before painting if you are using acrylic caulk — it will accept paint and blend in. If you are using silicone, caulk after painting, because silicone does not accept paint well and you want to avoid getting paint on it.

What is the difference between caulk and grout?

Caulk is flexible and stays slightly soft, so it can move with the materials it seals. Grout hardens solid and does not flex. Grout is for tile joints where movement is not expected. Caulk is for gaps between different materials or where movement happens.

Can I do caulking myself?

Yes, if the old caulk is already removed or minimal. Removing old caulk is the hardest part and is where most DIY jobs go wrong. If you are starting with a clean gap, explore new caulk is straightforward — you need a caulk gun, a smoothing tool, and patience to get a neat bead. Expect a learning curve on your first few feet.