Simple Solutions

How to Caulk Wide Cracks

By: Joe Truini
Using foam backer rod to fill a wide crack before caulking.

Using foam backer rod to fill a wide crack before caulking.

One of the best ways to save energy in your home is by caulking any cracks around windows and doors. While caulk alone can be applied to narrow cracks, gaps wider than 1/4” should be filled with foam backer rod first.

These flexible foam tubes are available at building supply stores in several diameters. Simply push the rod into the gap with a putty knife or painter’s tool until it is just below the surface then caulk over it.


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7 Comments on “How to Caulk Wide Cracks”

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  • Winnie Reed Says:
    February 8th, 2019 at 9:41 am

    Good video but I would like to see the finished product after adding the strip. I have a large gap between my counter top and back splash. I can’t get a smooth bead.

  • Brent Says:
    May 10th, 2018 at 3:50 am

    I was looking for tips on how to make a wide area of caulk look nice. This video applies more to deep cracks not wide cracks since he never shows caulking after putting the backer rod in.

  • Brian Says:
    July 8th, 2017 at 5:09 pm

    Hi- Does the foam backer rod work for large gaps in kitchens too? I have a large kitchen counter gap is why I ask.

  • JP Says:
    June 17th, 2016 at 8:38 pm

    Helpful, thanks. Very few handy sources of info on backer rod use.

  • Bill Kady Says:
    April 15th, 2016 at 8:11 am

    Do you have any ideas on why my three wooden garage doors with 20 years of a natural finish peeled after I refinished them with minwax spar outdoor urethane last year?

  • Erin Elizabeth James Says:
    April 2nd, 2016 at 12:27 pm

    Thank you for the clear, concise info on foam backer rods for caulking large gaps. Very helpful!

  • Paul Artman Says:
    September 23rd, 2015 at 1:07 pm

    Thank you for information (video) concerning backer rod and how to use. This was very helpful in a job of using mortar mix.

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How to Caulk Wide Cracks