New Bilco door. Old House Improvements:

Replacing An Old Basement Entry
With A New Bilco Door

In This Article:

An old wooden basement access door is demolished, some new concrete is poured to form a smooth level rim, and a new Bilco steel door is installed.

Related Info:
Skill Level: 3-4 (Moderate to Advanced) Time Taken: About 16 Hours.

By , Editor


Recently some friends who own an old house asked me to replace an old decrepit basement door with a new Bilco steel door.

The existing basement door was home-made, and poorly made too. 

There were many problems with this door, such as leaks, and general insecurity.


The underside of the door was badly decayed. All those white patches are fungal growth.


There were holes in the plywood door, and moss was growing on the wood. Moss growth is not a good sign, especially when it's on the south side of the house.


The concrete pad at the entry was acceptable but slightly cracked.


The wooden support framing (red arrow) was mostly intact. I could have simply made a better door, but the homeowners wanted something more secure and sturdy.


Using hammers and pry bars, I removed the door and all the plywood skin.

At this point I realized that the plywood and lumber was all pressure treated. This told me that the door was probably less than 30 years old.

In spite of this preservative, the wood managed to rot in places where it was exposed to the elements.

I suspect that the Chromated Copper Arsenate (CCA) preservative got washed away from years of rain dripping on the plywood door.

There was a large pile of dead leaves behind the far side. Fortunately these leaves were dry, otherwise there would have been some interesting flora and fauna growing in the "compost".


The good news: The side foundations were in excellent condition.

The bad news: The front foundation (red arrow) was thin, weak, and cracked. It also sloped sharply away from the side foundations, which meant that the new Bilco door would not have a uniform and flush surface to rest on.


The side walls of the entry foundation were made from stone rubble, just like the rest of the foundation. Most of this foundation was intact.


I used a sledge hammer to break up the front slab part of the foundation, being careful not to damage the stone rubble wall that extends a couple of feet below grade.

This front slab was basically a pile of rocks with mortar smoothed over the top.


I made some concrete forms from 2x4's (the lumber from the old door frame).

I placed some of the rocks from the old front slab into the forms, to reduce the volume of concrete I would need.

These rocks weren't just thrown into the hole. They were laid out to occupy the center portion of the slab. I tried to keep the rocks away from the form boards, so the slab would be 4 inches thick (or greater) around the perimeter, and at the center there would be some rocks embedded in the slab.

Also, before I put the rocks in place, I used a tamper to pack the soil down. This should help prevent settling later. 

I poured the concrete slab. This took 6 eighty-pound bags of Quickcrete. It was getting pretty late in the evening when I finally finished this slab.

For this small concrete slab I used:

  • a wheelbarrow for mixing,
  • a hoe (to mix the concrete in the wheelbarrow),
  • a small flat shovel (to help guide the concrete as it was poured), 
  • a small magnesium float (to "float" the concrete, or push the rocks below the surface) and
  • a broom to add the final texture (as is standard with outdoor concrete slabs).


Estimating Concrete:

To determine the number of bags of concrete, I first compute the volume of the slab, by multiplying the length by the width by the depth (or thickness). Of course, this can only be done if the units of measure are all the same, either in inches or feet. (Multiplying inches times feet results in unusable information.)

If I use dimensions measured in inches, I multiply the three dimensions together to get the volume in cubic inches. Then I divide that number by 1,728 (which is 12x12x12, the number of cubic inches in a cubic foot) to get the volume in cubic feet.

Concrete weighs between 120 and 140 pounds per cubic foot. If I multiply the volume (in cubic feet) by 120, I find that I get a good estimate of the total weight of dry concrete mix I need. Then I can divide the total weight by 80 pounds to determine the number of 80 pound bags to buy, or I can divide by 60 to get the number of 60 pound bags I'll need, whatever the store carries.



Concrete pad for Bilco door. The next day the slab was hard enough to walk on, though still soft enough that it could be chipped if I wasn't careful.


I could tell that the rough surface of the stone wall was going to keep the Bilco door from meeting the house correctly. There were a couple of high spots, which I shaded in black with a marker pen (red arrow).

I used a 4 inch diamond wheel on a grinder to cut away the rock. This took a few minutes.


I assembled the door extension and set it in place on the foundation.


I placed the extension close to the house and marked the mounting hole locations on the stone foundation.

Then I used a hammer-drill and a carbide masonry bit to drill some mounting holes in the foundation wall. The Bilco door came with some large plastic anchors for mounting to masonry.


Parts of Bilco door frame. The main parts of the Bilco door frame. 
  • Two sides,
  • a back rail, 
  • a front rail.


I assembled the door frame according to the instructions. There were two bolts at each corner. Bilco door frame assembled before installation.


At the upper corners there was some special caulking that had to be applied to the lower pieces (the triangle-shaped sides).

This caulking (provided with the door hardware) was just a small strip of soft pliable goo that got squished down as the screws were tightened.


A bottom corner. Assembly of the frame was simple and took about 15 minutes.


Bilco door set in place on foundation. I set the frame in place to test the fit.

Note how there is green paint on the back side. I pre-painted the side that would be inaccessible after installation. Bilco says to paint the entire door and frame with an oil-based paint, or the metal will rust.


Attaching the extension to the house:

I pried up the metal flashing that remained from the previous basement door installation, and I drove in a couple of small lag screws into the wood structure of the house.

Fastening Bilco door to house.

Flashing is important: Careful attention must be given to the point where the siding meets the top of the Bilco door.

Attaching Bilco door to stone foundation of old house. I drove lag screws into the plastic anchors that I had earlier installed in the stone foundation.

This completed the installation of the extension.

I then placed the Bilco door frame on the foundation and aligned the mounting holes with those on the extension. I also slipped some strips of sill seal foam (the blue stuff in the photos below) under the door frame. I poked a screwdriver through the mounting holes to rip openings in the thin foam.

Using a felt tip marker I marked the mounting hole locations on the concrete foundation.

I removed the frame and drilled large holes with a hammer drill and a carbide masonry drill bit.


I tapped the plastic anchors into the holes.


I set the door frame back into position and secured it with the small lag screws provided.


Using a utility knife I trimmed away the excess sill seal foam.


There were a couple of smaller screws that held the front section of the frame to the concrete.


With the frame attached, I installed the doors.


Each door has two hinges, and each hinge is held in place with a steel pin (red arrow). A cotter pin prevents the pin from falling out.


Bilco doors are very heavy, and if the torsion rod springs are not installed correctly somebody could get badly hurt. Follow the instructions included with the Bilco doors.

The photos that I show here may not be an accurate representation of the installation sequence of the 4 torsion springs that help lift the doors.

These photos portray some of the installation steps for the torsion rods on the right hand door.

After the first rod was installed, (which on the right hand side is the lower rod), I hooked the "J"-shaped end of the second torsion rod into the hinge bracket...


... and then I slipped the "L"-shaped end into the retaining socket.


This photo of the right-hand door shows how the lower torsion spring (the black rod on the right) is behind and above the upper torsion spring.

The upper rod holds the lower rod in place. The rod that goes in front and below (and holds the other rod in place)  must have its "L" end pointing downward.

The torsion rod installation for the left hand door is similar, but different. The first rod installed is the upper, and the lower rod holds the upper in place.

On both doors the rod with the "L" end that points downward is below the other rod (which has the  "L" end that points up).

The torsion rods have number 1 and number 2 markings on their plastic parts. Also, Bilco includes a small tube of special grease to lubricate the torsion rods where they rub against the steel hinges.

The doors after installation.

 The torsion rod springs make lifting the doors almost effortless.


Using a can of expanding foam insulation, I filled the gaps behind the steel extension and the rough stone foundation.

After the foam had cured completely (a couple of hours) I trimmed away the excess with a sharp knife. Then I covered the cut foam with siliconized acrylic latex caulk.


I later painted the doors with oil-based paint, as per Bilco's instructions. The doors are primed at the factory and must be painted to keep them from rusting.

It took about a quart of paint.

Completed and painted Bilco basement entry door.

I also installed a Bilco-supplied keyed lock (an option that cost about $60). Installing this lock involved drilling several holes through the thick steel doors. The holes need to be located rather precisely, and Bilco provides a paper template to lay out the holes. But... drill bits tend to wander when drilling in steel, so achieving precision was not easy. I found that making heavy dimples with a center punch was very important.

I recall that it took me several hours to install just the lock.

There is a simple sliding drawbar locking mechanism on the inside of the Bilco door (which is standard equipment), so the door can be locked from the inside. But the owners of this house wanted to be able to access the basement from the outside, so they needed the additional keyed lock.

The completed and painted door adds a degree of security and convenience to the older home. In fact, I would seriously consider adding this type of exterior basement access to any house.

Having spent plenty of time around this house, I find it very convenient to be able to walk directly into the basement without having to go through the house.

From the perspective of a mechanical engineer, I find the Bilco door to be well designed and very sturdy. I understand that Bilco has been making these doors for many decades, and I'm sure they have fine-tuned their design over the years.

The Bilco door is not cheap. This "size C" door with a 12 inch extension and a keyed lock was almost $700. We bought this Bilco door at a local lumberyard. These are normally special-order items that may take a few days or weeks to arrive.

Web Links: Bilco Company web site.



Tools Used:

  • Cordless Drill/Driver
  • Basic Carpentry Tools
  • Basic Concrete Tools
  • Hammer-Drill
  • Ratchet Wrench and Sockets


Materials Used:

  • Bilco Door
  • Bilco Door Extension
  • Bilco Door Lock
  • Expanding Foam
  • Caulk
  • Concrete
  • 2x4's for Concrete Forms

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Copyright © 2003

Written March 28, 2003