Caulking is not glamorous and it is not expensive, which is exactly why it gets deferred. It is also one of the most common places water gets into a house.
Where sealant matters
Anywhere two different materials meet, they move at different rates. Brick and aluminum window frames expand and contract differently in a Chicago summer, which means the joint between them opens and closes all year. Sealant is the flexible part that keeps that joint closed while it moves.
The joints worth checking on almost any house: window and door perimeters, control joints in the brickwork, where brick meets siding or trim, around vents and hose bibs, and the transition between the foundation and the wall above.
Why cheap caulking fails
Two reasons, nearly every time.
- The old sealant was not removed. New caulk applied over failed caulk is bonded to something that has already released, so it goes when that goes.
- There is no backer rod. Sealant needs to be roughly twice as wide as it is deep, and it needs to bond on two sides only. Gun it into a deep joint with no rod and it grabs three sides, cannot stretch, and tears.
What we use
Polyurethane sealant for most masonry joints, because it stays flexible and takes paint. Silicone where the joint needs to shed water and will not be painted. Not acrylic latex, which is what comes in the cheap tubes and turns hard and chalky within a few seasons of Chicago weather.
Every joint gets the old material cut out, the substrate cleaned, backer rod sized to the gap, and a tooled concave finish that sheds water rather than holding it.
Signs you need this work
- Cracked, split or chalky caulk around windows and doors
- Sealant pulling away from one side of the joint
- Drafts near window frames
- Water stains on interior sills
- Gaps where brick meets siding, trim or stone
- Caulk that has gone hard and lost all flexibility
What's included
- Complete removal of the old failed sealant, not caulking over the top
- Joint cleaning and priming where the substrate requires it
- Backer rod installed so the sealant can flex correctly
- High-grade polyurethane or silicone sealant appropriate to the joint
- Tooled finish, not a smeared bead
- Color matched to the adjacent material
How we do it
- 1
Survey
We identify every joint that has failed, including the ones that are easy to miss like control joints and material transitions.
- 2
Removal
The old sealant comes out completely. Caulking over failed caulk is the most common shortcut in the trade and it never holds.
- 3
Backer rod
Correct-diameter rod goes in so the bead is the right shape and can stretch without tearing.
- 4
Seal and tool
Quality sealant is gunned in and tooled to a clean concave finish that sheds water.
Common questions
How often does exterior caulking need replacing?
Good polyurethane sealant, installed correctly with backer rod, lasts 10 to 20 years. Cheap acrylic latex caulk applied straight into a deep joint often fails in 3 to 5.
Why does new caulk keep cracking?
Almost always because there is no backer rod. Sealant needs a specific width-to-depth ratio to flex. Without rod it bonds to three sides instead of two, and tears the first time the joint moves.
Can you caulk over the old caulk?
You can, and it will fail. The new sealant is only as good as whatever it is stuck to, and it is stuck to something that has already let go.
Is caulking part of a tuckpointing job?
Not automatically, and it should be. If we are already repointing a wall, adding the window perimeters and control joints is inexpensive and closes the other half of the water path.