Polyurethane Caulk – Possibly the Best Sealant

The ultimate sealant could possibly be polyurethane caulk. This is a bold claim, especially with so many types of sealants on the market. This sealant has taken all the best attributes of all other sealant types and put it into a convenient, single component cartridge ready to tackle your most difficult, or even impossible, caulking requirements.

Urethane caulk can be difficult to apply. It has a sticky, putty like, consistency and requires mineral spirits for both tooling and clean up. But, it will cure into a paintable rubber capable of stretching 300% or more. Some manufactures boast as much as 1200% elongation. Plus, it has very high tensile strength. Can adhere to almost all types of surfaces. Including concrete, wood, glass, plastic and metal.

This incredible ability to adhere to so many dissimilar materials is just one of its features. Very important when trying to create a seal between various materials that expand or contract at different rates. Plus, urethane caulk has excellent chemical resistance.

 

No Mixing or Special Equipment Required

Available in single component cartridges are designed for both standard 10 ounce and 1-quart caulking guns. You have a choice of non-sagging or self-leveling formulas.

  • Use the non-sagging formula for expansion joints in concrete block, gaps in wood siding and around windows or doors.
  • Self-leveling formulas have a very high resistance to abrasion. A perfect match for control joints in concrete floors, especially garage floors prior to the application of epoxy.

 

Polyurethane caulk can be applied to very large gaps, 1 inch or more, and not loose its ability to create a perfect seal. I have used Sonneborn NP-1 for years on commercial buildings and garage floors prior to the application of a high performance finish, with perfect results.

Although this sealant is difficult to use and will cost considerably more than standard caulking, the benefits will be worth it in the long run. It’s possible this type of caulking could outlast the paint job and the person who applied it.


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7 Comments

  1. George Kenter
    Posted September 5, 2016 at 5:43 pm | Permalink

    I used self-leveling caulk, a premium-grade polyurethane sealant, on expansion joints on my concrete parking pad, with poor results, even using baker rods, due to wide variation in depth and width. Some parts of the job are quite low, giving an uneven up and down look. Other than attempting to finish with more of the same (I found the product hard to use), is there another type of caulk I can apply in about a week to even the appearance?

  2. J L MacDougall
    Posted September 13, 2016 at 12:25 am | Permalink

    What type of paint is recommended for polyurethane caulk? I tried a water-based one and that doesn’t work.

    • Posted September 13, 2016 at 6:38 pm | Permalink

      Polyurethane sealants require priming before painting with normal house paints. Try a good universal oil base primer, like Zinsser Cover Stain. Allow to dry then paint as normal.

      Recommended coatings without primer can include epoxies and elastomerics. Always consult the product label or with the manufacture for more info.

  3. Daniel
    Posted March 30, 2017 at 4:27 pm | Permalink

    Can I use a form of eurethane finish over the top of np1 filled joints. not sure if there will be any reactions since they are both forms of eurethane. thanks.

    • Posted April 1, 2017 at 2:27 pm | Permalink

      Should be fine but NP-1 can be tricky. Test if possible. If unsure, prime before painting.

  4. Duncan Hoge
    Posted October 2, 2017 at 6:01 pm | Permalink

    We had some damage to a masonry chimney and needed to put polyurethane caulk in the mortar joints. Looks it will do the trick, but our repairs stand out, since the color of the caulk does not match the original mortar. Can the caulk be stained or is paint the only choice? Thank you for your answer….

    • Posted October 3, 2017 at 3:30 am | Permalink

      The caulk can’t be stained. If painting, make sure to prime the caulking first with an oil based primer (some poly sealants don’t take paint well). Read the tube for painting instructions.

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