How to Seal Outside Cracks on Your Home

Sealing cracks on the outside of your home is important to prevent rainwater from seeping in and causing rot and mold.

Sealing cracks also increases energy efficiency and lowers utility bills by reducing air infiltration into your home.

To seal cracks in your home:

  • Fill small cracks and holes with quality, exterior-grade caulking.
  • Fill larger cracks and holes using expandable spray foam.

If you plan to paint over the caulking, be sure the caulking you use is paintable.

Watch this video to find out more.

Further Information


Sealing up cracks on the outside of a home keeps moisture out and prevents outside air from influencing the inside conditioned air. For larger openings use an expandable foam spray from a can to fill in the voids. Smaller openings can be filled with caulk. Before you select your caulk think about how it will look after the gap is filled. If it will need to be painted, be sure to choose a “paintable” caulk so your touch-up will stick.


  1. I left a comment this morning about how foaming under the sill, as demonstrated in the video, can cause moisture problems and that perhaps that portion of the video should be edited out. The comment was up for all of about five minutes and was then edited out, yet that portion of the video remains.

    If I’m wrong, how about answering that in the comments rather than deleting the comment pointing out potentially bad advice?

    • Hi Jeremy,
      Sealing up cracks and holes on the outside of your house not only reduces air infiltration, which saves energy on heating and cooling; it prevents rainwater from entering the wall cavity, which would cause rot and mold inside the walls. If your home was constructed properly, sealing between the bottom row of siding and the foundation, is not as important for preventing rainwater from entering, since the siding should overlap the masonry foundation, but it can help reduce air infiltration and enhance the envelope around your home. Moisture isn’t meant to drain out from the interior of the house under the sill, so sealing up the gap won’t cause any moisture problems inside your home. If you do have moisture draining out of the interior of your house between the bottom row of siding and the foundation, you have a serious problem that should be addressed before it causes major rotting to the sill and framing. While it’s important to provide adequate ventilation in your home through the use of kitchen and bathroom vent fans to remove excessive moisture in the air from cooking and bathing, other areas of air infiltration only serve to weaken the envelope of your house and allow conditioned air to escape and unconditioned air to enter.

  2. Thanks Ben. This is one of the few sites I turn to for interesting and accurate information, so I appreciate what you guys are doing.

    Having said that, I do weatherization work, so I am quite familiar with air-sealing and moisture issues.

    I also know that modern vinyl/aluminum siding is typically designed with small weep holes at the bottom so that any moisture that gets behind it can escape. They do that because despite best efforts or intentions, water does get behind the shingles/siding.

    Sealing the sill plate is the right thing to do, but sealing the bottom row of siding, as in the video, is akin to caulking over weep holes in a window – you’re trapping the water in there. You might want to check with some air-sealing pros in your area who will confirm this.

    • Jeremy,
      Thanks for the feedback and bringing up an important point about allowing vinyl, and particularly aluminum, siding to breathe and move by not caulking the weep holes or joints. Due to their thin nature, vinyl and aluminum siding are sensitive to changes in temperature, which may cause condensation to form behind the siding. While it usually isn’t enough to cause water to run out of the bottom, the weep holes do allow any moisture that might form to evaporate. The video above shows expanding foam being used to fill large gaps behind the bottom row of wood siding, which doesn’t experience the same condensation problems as vinyl and aluminum.

  3. Thanks for the video, but I would advise against sealing the gap where the frieze board (or cladding) meets the brick. Any moisture that gets behind the cladding — and it will! — must be able to dry and drain. Caulking or foaming that gap will prevent proper ventilation (drying) and egress (draining) required for said purposes.

  4. My house is ten yrs old,and steel house has been settling since I’ve built.theres cracks on all of my outside walls and my foundation as a crack on the same side my base boards are coming unglued as I would say.what do I need to do to fix this problem.

  5. I would like to know where Allen is, I have not seen him on the last few shows. I think he is someone who complements you and has a good insight on home improvements. Your daughter is very good on the show and you have taught her a lot of home improvement techniques. I like to watch the show with you and Allen working hand and hand on solving a home owners problems.
    Thank You

  6. I like to show because it deals with real problems real homeowners have with their homes and repairs and what normal people would be doing to their homes every day.Everybody does a good job keep up the good work I sure appreciate it.

  7. My house is 13 yrs old. It had vinyl siding on it when I purchased it. I replaced the siding with hardi plank, but the wall insulation under the vinyl siding was just a foam board. I wanted to upgrade the insulation and put a vapor paper in but the contractor said they couldn’t do either as there wasn’t enough room. My house is so cold during the fall and winter. What can I do to check if the insulation in the walls is adequate? Also, the garage wasn’t insulated, so I added insulation in the attic , but the walls had sheetrock on them, so they are not insulated, How can I insulate the walls without removing the drywall? thank you

  8. I have a very new house within a metal building, one type of “ba.rndominium”. Is it advisable to caulk on the outisde bottom between metal sididng and slab on piers?

    • Hi, Joe,

      Danny says, “Yes, I think this would be a very good idea. Clean it thoroughly first so the caulk would adhere. The more you conceal the envelope of the building, the better off your area.”

      Good luck!

  9. frame house on a cement slab. One area in back of house, northern side, when its a cold winters night here in The desert of Abq nm, if something is lying against the floor against the wall, when you pick it up it will so cold it can feel wet. Any ideas? Is a 35 yr old home, first owner, Impeccably maintained. To the point people and realitors ask us if we want to sell. Spouse checked, he says nothing wrong. I feel there has to be something. outside is brick facade in front, rest is that board they put up as siding. Have all brand new rated triple pane windows, 3 year old new carpet with upgraded cushion. Thank you


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