Should You Paint the Gaps in Wood Siding? Here’s What You Need to Know

When it comes to painting exterior wood siding—like board-and-batten or lap siding—many homeowners wonder: Should I paint or fill the gaps between the boards? The short answer? No, not unless specifically instructed by the manufacturer. Those gaps exist for a reason.

Here’s what you should know before tackling your exterior siding project.

Why Do Wood Siding Gaps Exist?

Wood siding expands and contracts with seasonal changes in temperature and humidity. The gaps between the boards are built-in features, not flaws. They:

• Allow for natural expansion and contraction

• Prevent warping, cracking, or buckling

• Encourage air flow to reduce moisture buildup and rot

Closing these gaps with paint or caulk can disrupt this natural movement—and lead to expensive damage.

Can You Paint the Gaps in Wood Siding?

You can paint around them, but don’t fill them. Here’s how to do it properly:

1. Avoid Filling or Bridging the Gaps

• Don’t apply thick coats of paint that may "glue" boards together.

• Avoid products that could harden in the gap and block movement.

2. Use a Thin, Even Paint Application

• Apply high-quality exterior-grade paint specifically made for wood.

• Focus on coverage without compromising flexibility.

3. Know When (and Where) to Use Caulk

• Gaps between boards should generally be left open.

• Caulk can be applied where siding meets trim or corners, but not across slat joints unless the manufacturer recommends it.

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What Happens If You Fill the Gaps?

• Trapped moisture can lead to mold and rot

• Restricted board movement can cause splitting and warping

• Increased maintenance due to paint cracking or peeling

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Best Practices for Painting Wood Siding

To get the longest life out of your exterior paint job and protect your wood siding:

• Clean and prime the wood before painting

• Preserve the existing gaps without overcoating

• Use flexible, paintable exterior sealants only where necessary

• Inspect annually to remove debris and check for signs of moisture

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Still Unsure? Ask a Pro

Every siding project is a little different. If you’re unsure how to proceed—or if your siding was previously caulked or painted improperly—consult a painting professional or check the original manufacturer’s guidelines.

At Axcell Painting, we specialize in long-lasting exterior painting that respects the natural movement of wood siding. Get in touch if you’d like advice or a quote for your next project.

Looking to paint your wood siding without risking damage?

Get a free quote and let’s talk about the best approach for your home.