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How to Seal a Bilco® Bulkhead Cellar Door

How to Seal a Bilco® Bulkhead Cellar Door

A Step-by-Step Guide

The Bilco cellar door is a popular choice for homeowners with basements or cellars. It provides easy access to below-ground storage areas and can also serve as an emergency exit. However, one common issue with these doors is the potential for water leakage and drafts. Sealing your Bilco cellar door is essential to protect your basement or cellar from moisture, pests, and energy loss. In this comprehensive guide, we'll walk you through the step-by-step process of sealing your Bilco cellar door effectively.

Why Seal Your Bilco Cellar Door?

Before we dive into the sealing process, let's understand why it's crucial to seal your Bilco cellar door:

  1. Water Infiltration: An unsealed Bilco door can allow rainwater, melting snow, or groundwater to enter your basement or cellar, leading to water damage, mold growth, and structural problems.

  2. Energy Efficiency: A poorly sealed door can result in drafts and heat loss, making your home less energy-efficient and increasing your utility bills.

  3. Pest Prevention: Gaps and openings in the door can provide an entry point for pests like rodents and insects, potentially causing infestations in your basement or cellar.

  4. Security: Properly sealed doors can enhance the security of your home by reducing the risk of unauthorized access.

Tools and Materials You'll Need

Before you start sealing your Bilco cellar door, gather the necessary tools and materials. Here's what you'll need:


  1. Screwdriver or drill
  2. Caulk gun
  3. Putty knife or scraper
  4. Utility knife
  5. Tape measure
  6. Level
  7. Paintbrush


  1. Weatherstripping kit 
  2. Expanding foam sealant
  3. Silicone caulk
  4. Exterior-grade paint or sealant (optional)

Step-by-Step Guide to Seal Your Bilco Cellar Door

Follow these steps to effectively seal your Bilco cellar door:

1. Inspect the Door

Start by inspecting your Bilco door for any existing damage or gaps. Look for cracks, loose hinges, or damaged weatherstripping. Address any structural issues before proceeding with the sealing process.

2. Remove Old Sealants

If there is old caulk, paint, or sealant on the door, use a putty knife or scraper to remove it. Ensure that the surface is clean and free from debris before applying new sealants.

3. Install Weatherstripping

Weatherstripping is an effective way to seal the gaps around your Bilco door. Measure the dimensions of the door frame, and cut the weatherstripping to fit accordingly. Apply the weatherstripping to the door frame, ensuring a snug fit. You can use screws or adhesive to secure it in place. Pay special attention to the bottom of the door frame, as this is a common area for drafts and water infiltration. Consider adding a door sweep to create a better seal at the bottom.

4. Apply Expanding Foam Sealant

Expanding foam sealant is ideal for filling larger gaps and cracks around your Bilco door. Use a low-expansion foam suitable for outdoor use. Carefully follow the manufacturer's instructions when applying the foam. Start by shaking the canister well, attach the applicator straw, and insert it into the gaps or cracks. Gently squeeze the trigger to release the foam. Be cautious not to overfill, as the foam will expand. Once the foam has expanded and dried, trim any excess with a utility knife to create a smooth, even surface.

5. Caulk Around the Edges

Silicone caulk is an excellent choice for sealing gaps and seams around the door frame. Apply a bead of caulk along the perimeter of the frame where it meets the concrete or wall. Use a caulking gun for precision. Smooth the caulk with a damp finger or a caulk tool to create a watertight seal. Pay close attention to the corners and any joints where the frame meets the wall.

6. Check and Adjust the Door Alignment

Inspect the alignment of your Bilco door. Use a level to ensure that the door is properly positioned and closes tightly against the weatherstripping. If necessary, adjust the door hinges to improve alignment and create a secure seal. Tighten any loose screws or hardware.

7. Paint or Seal the Door (Optional)

While not essential for sealing, painting or sealing the Bilco door can provide an extra layer of protection against the elements. Use an exterior-grade paint or sealant that is suitable for your door's material. Apply a coat evenly, following the manufacturer's instructions. Allow sufficient drying time before reattaching the door hardware and using the door.

8. Regular Maintenance

Regular maintenance is key to ensuring the long-term effectiveness of your Bilco cellar door seal. Inspect the door periodically to check for any signs of wear, damage, or deterioration. Reapply caulk or sealant as needed, and replace weatherstripping if it becomes worn or damaged.

Additional Tips for Bilco Door Maintenance

To further protect your Bilco cellar door and maintain its functionality, consider these additional tips:

  1. Keep the Drainage System Clear: Ensure that the drainage system around the door is clear of debris and functioning correctly. Proper drainage will help prevent water from pooling around the door.

  2. Lubricate Hinges and Locks: Regularly lubricate the hinges and locks of your Bilco door to keep them in good working condition. Use a silicone-based lubricant for smooth operation.

  3. Secure the Door: If your Bilco door is an entry point to your home, make sure it is securely locked when not in use to prevent unauthorized access.

  4. Monitor the Basement or Cellar: Periodically check your basement or cellar for signs of moisture, pests, or other issues. Promptly address any concerns to prevent further damage.


Sealing your Bilco cellar door is a vital step in maintaining a dry, secure, and energy-efficient basement or cellar. By following the steps outlined in this guide and regularly inspecting and maintaining your door, you can ensure that it effectively protects your space from water infiltration, drafts, and unwanted pests.

Investing time and effort in properly sealing your Bilco cellar door will not only enhance the comfort and functionality of your basement but also contribute to the long-term health and value of your home. Enjoy peace of mind knowing that your basement or cellar is well-protected and ready for any season.

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