How to Caulk Hardie Plank Lap Siding Field/Butt Joints-DIY/Post-Construction

#jameshardie #caulking #howto

How to Caulk Hardie Plank Siding Like a Pro | Step-by-Step Guide - Joints, Post Construction

Did a contractor put nails in too close the ends of your Hardie Plank siding? Any flexure over time will break the corners & cause cracks. If you don't want to remove the whole board of siding, then try this simple trick! Stick around to learn how this quick fix can save you money and keep your home looking great. Let’s dive in!

First, I chose this caulk because it has 25% flexibility - compared to silicone-based caulk.
- House built before 2008, has no flashing, & and isn't ColorPlus® technology, so okay to caulk.
- Afterwards, do NOT use sandpaper on Hardie Plank.
- Let dry (usually 24 hours).
- Wash & paint.


Time Stamps:
00:00 Choice of Caulk
00:12 Clean & Prep the Area
00:40 Caulking & Smoothing
02:45 Final Look


I created this video with the YouTube Video Editor
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Caulking Hardie Plank siding (also known as James Hardie fiber cement siding) helps seal gaps and prevent water infiltration, improving the longevity of the siding. Here’s a step-by-step guide to caulk Hardie Plank siding properly:

Materials Needed:

High-quality exterior caulk (preferably silicone or paintable acrylic latex)
Caulk gun
Utility knife
Painter's tape (optional)
Caulk smoothing tool or a damp rag
Ladder (if needed)
Clean rags or paper towels
Gloves (optional)

Steps to Caulk Hardie Plank Siding:

Prepare the Surface:
Clean the area to be caulked. Remove any dirt, dust, or old caulk using a rag or sponge. Make sure the surface is dry before you begin caulking.
How to Caulk Hardie Plank Siding Like a Pro | Step-by-Step Guide - Joints, Post Construction

Choose the Right Caulk:
For Hardie Plank siding, it's important to use a high-quality exterior caulk that is designed for outdoor use and that can withstand the elements.
Silicone-based caulk is durable but can’t be painted.
Acrylic latex caulk is paintable and works well if you plan to paint over the caulk once it’s applied.

Load the Caulk Gun:
Cut the tip of the caulk tube at a 45-degree angle to create an opening just large enough for the gap you are caulking.
Puncture the inner seal of the caulk tube using a nail or similar tool.
Load the tube into the caulk gun.

Apply Painter's Tape (Optional):
If you want a neat, clean line, apply painter's tape along the edges of the area to be caulked. This will prevent excess caulk from smearing onto the siding.

Apply the Caulk:
Hold the caulk gun at a 45-degree angle to the gap.
Squeeze the trigger and move the gun along the gap. Apply a consistent bead of caulk along the seam where the Hardie Plank boards meet each other, around windows, doors, and trim.
Don’t apply too much at once; work in sections to avoid the caulk drying out before smoothing it.

Smooth the Caulk:
After applying the caulk, smooth it with a caulk smoothing tool or a damp finger to ensure it fills the gap evenly and has a clean finish.
Wipe off excess caulk with a damp rag or paper towel. If you used painter's tape, remove it while the caulk is still wet for a clean edge.

Allow the Caulk to Dry:
Follow the manufacturer’s instructions on drying time. Most caulks require a few hours to dry completely. If you're painting over the caulk, let it cure for at least 24 hours before applying paint.

Inspect Your Work:
Once the caulk is dry, check for any missed spots or areas that may need a second application. Touch up any areas as needed.

By following these steps, you'll create a watertight seal that helps to protect your Hardie Plank siding and keep it in good condition.