How To Measure For A Bilco Basement Door

Planning to install a Bilco door to access your basement? It will help if you select the right door size. You should pick the Bilco door size to allow easy and unobstructed access to the basement. To help you proceed, we've consulted the experts on how you can measure a Bilco basement door.

When you are ready to purchase a Bilco basement door, follow the steps below to get the exact measurements of the door:

  1. If you need to replace an old Bilco door, remove it first before getting its dimensions.
  2. You have to measure the inside and outside widths and lengths for a new door. 
  3. Then, get the distance from the top of the areaway foundation to the top of the basement opening.
  4. After recording the measurements, pick the door size that is not longer and wider than the inside opening.

By selecting the right door size, you can prevent problems that might damage the basement. You can efficiently operate the door if it fits in the foundations. Custom sizes for the doors are not available. Learn more about Bilco door sizes as you read along.

Green basement doors outside a brick home, How To Measure For A Bilco Basement Door

What Size Is A Standard Bilco Door?

It is crucial to get the correct dimensions before buying a door. You should have enough space to move large furniture to the basement and pathway for an egress.

Bilco offers standard sizes for two series of their basement doors. These are the Classic and Ultra series. You can refer to the table below for the available sizes from smallest to largest:

Size Dimensions (Width x Length x Height) Door Opening (L x W)
O 47 x 58 x 30 inches 58 X 40 inches
B 51 x 64 x 22 inches 60 X 44 inches
C 55 x 72 x 19.50 inches 67 X 48 inches
SL 51 x 43 1/4 x 52 inches 60 X 44 inches

If you buy the Ultra series, it is only available in size C. If the door size is insufficient, you can buy extensions. By doing so, you can increase the door frame length to accommodate a larger opening.

But if the door sizes are big, you can reduce the inside width with foundation plates. You can do so as long as the width of the inner areaway is 55 inches and above.

Read further on how you can measure the Bilco door for your basement.

How To Get The Size Of A Bilco Door

Bilco doors are available for flat foundations and sloped masonry walls. Based on the Bilco basement order form, here are the steps to follow to get the correct door size:

  1. You can simply remove the old door and get its dimensions for door replacements.
  2. If you bought a new door, start measuring the inner (W1) and outer (W2) areaway widths.
  3. Then get the lengths of both inside (L1) and outside (L2) areaway foundation.
  4. Also, measure the height (H1) for the door. Measure by starting from the top of the areaway foundation to the top opening of the basement foundation.
  5. After recording all the measurements, you can now choose the suitable Bilco door size.

In the selection process, take note of the following tips:

  • Pick a door size that is at least 4 inches wider than W1 but not wider than W2.
  • Choose at least 2 inches taller than L1, but not longer than L2.
  • For the height, you should find a size taller than H1.

Furthermore, a wider and longer measurement than the inner opening allows secure closure. As a result, the door frame will attach tightly to the foundation.

How Much Does It Cost To Install A Bilco Door?

Besides the door's dimensions, you should also account for the installation costs. According to Home Advisor, it will cost around $1,100 to $6,000 for Bilco door installation. You also need to budget for the professional fees you will incur. You might need a certified installer to avail of the warranty.

Bilco door prices range from $500 to $750. This price will bloat due to the preparation of the door frame and stairs if there is none. You might spend more to install the door without the necessary foundation. For new houses, you can include the installation in the initial construction of your home.

Also, you should include the costs of basement accessories for the door. You might need extensions, foundation plates, or stair stringers. If you want to save on installation, you can choose a powder-coated variant to skip the painting.

To get other relevant costs, read this article: How Much Does It Cost To Install Bilco Basement Doors.

Does My Basement Need A Bulkhead?

A bulkhead door is typical for basements. It allows access to and from the basement without passing through the main level of the house. The usual foundations are concrete or stone.

Bulkhead doors can either have one or two doors. You will need to swing it open with the handles on both sides of a door leaf. With doors closed tight, you can avoid water leaks and debris coming from above the surface.

The bulkhead is usually on an angled opening if you decide to add one for your home. This feature should include a stairway going down to the basement level. You might need to spend the installation of necessary foundations before buying the door.

Take note, though, that a basement bulkhead door has its advantages and disadvantages.


Here are some benefits of adding a Bilco door:

  • Residential Code Compliant - Bilco doors are IRC 2018 code compliant. The door serves as an egress in times of emergency and has weather-resistant properties. Some state building codes have other specific requirements. For instance, the doors must open outwards and directly access a basement bedroom.

  • Weathertight - With sloped and flanged construction, Bilco doors are weathertight. It keeps the areaway dry and prevents the binding of ice and snow on the door. You can also insulate the bulkhead to restrict the cold air coming into the basement. In that case, it will help in the efficient temperature control in the basement.

  • Long-lasting Composition And Finish - A Bilco is a rugged steel door that lasts for decades. You can also avail of the product warranty when you meet the conditions. You can choose between a Sherwin Williams baked primer or an optional powder coating. Both of these finishes create a durable protective layer for the door.

  • Added Security - The doors also provide security against trespassers. It has a slide bolt lock with internal mounting flanges and a keyed lock for external access.

  • Function And Mobility - Installing a bulkhead door is great for both finished and unfinished basements. A finished basement with a bulkhead door can improve the functionality of your home. If you plan to furnish an unfinished area in the future, you can easily mobilize people and fixtures to and from the basement.


One problem with Bilco doors is the gaps on the undersides of the door. Water and moisture can leak into the basement. Adding a weatherstrip on the door is not sufficient. You have to do the necessary sealing and waterproofing of the door foundation and stairway.

You can also install a drainage system on the bottom of the door to protect the basement from water damages. Check the gutters above the areaway if leaves and other debris cause clogging. Another solution is to use the door frequently to let excess moisture evaporate.

For more information, check out this post: Are Bilco Basement Doors Watertight?

How Long Do Bilco Doors Last?

Bilco doors will last long. The Ultra series can last for 10 years, while the Classic series is around 5 years. The powder coating of the doors prevents the chipping or fading of the paint. Also, you can use the door for longer with proper maintenance.

It is best to do regular maintenance during spring and fall. You will also need to use a red-oxide primer to keep the paint on the door. You can refer to the operation and maintenance instructions from Bilco to guide you.

In Closing

Green basement doors outside a brick home, How To Measure For A Bilco Basement Door

Bilco basement doors have standard sizes. You have to get the correct measurements before selecting the door that fits in your basement. It will help if you pick the right door size to avoid more expenses. The installation is expensive, especially if you hire a certified basement door installer.

A bulkhead door is a good investment for your basement. Whether finished or unfinished, a bulkhead door has more benefits than drawbacks. You can use the basement door for longer with the proper maintenance. With Bilco, you can have a durable, secure, and code-compliant basement door.

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