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Caulk is a waterproof filler and sealant used in building work and in repairs to protect the substrate and improve appearance. When caulk fails to adhere, it can result in unsightly cracks into which moisture can seep and cause a secondary, and serious problem.

This failure can happen for a variety of reasons. The most common cause of caulk failure is expansion and contraction, which is a normal and expected occurrence that happens over time. We have seen excessive caulk failure occur with the most popular brand of siding used by today’s builders and remodelers: HardiePlank®. HardiePlank® is great siding, it tends to hold paint longer than any other siding. It also does not require back brushing or rolling, under normal circumstances.

Before 2008, HardiePlank® siding was installed differently than it is today. Caulking was used in the field joints (the joints where the siding boards meet up). This failed because of excessive expansion and contraction (the boards are quite flexible). The manufacturer of HardiePlank® remedied this serious issue by requiring installers to install flashing behind the field joints making caulk unnecessary at these joints.  Thankfully, as a result of this change in policy, newer homes with this siding should not have a caulk failure problem. Unfortunately, because the “fix” for this problem is not widely known by installers and painters, we still run across this type of caulking problem, even in homes built after 2008.

If you are a homeowner with HardiePlank® siding and your siding does not have flashing, it is important to understand that the caulk can still fail even after it is replaced. We cannot guarantee results when working with this type of siding, because the problem is with the product, not with the paint.

There are some things you can do to minimize the issue, however.

  1. Replace caulking as soon as you notice it failing. We use an elastomeric caulk as recommended.
  2. Touch up the paint after any caulking repairs – this will help the appearance and the seal.
  3. In extreme cases, siding replacement may be needed.

Home renovations are stressful even under the best of circumstances. Things like caulk failure can complicate your otherwise straightforward job; but more knowledge about your property and your potential problems can help to assure a quality end product. If you have HardiePlank® siding, check it often for caulk failure and hire a trusted and well-informed painter whenever you choose to re-paint.

Until next time,




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