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.
3-4 (Moderate to Advanced)
About 16 Hours.
Bruce W. Maki,
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
|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
||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 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
- 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
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.
||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
||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.
||At the upper corners there was some special
caulking that had to be applied to the lower pieces (the
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.
||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.
Flashing is important: Careful attention must be given to the
point where the siding meets the top of the Bilco door.
||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
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
||... 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
||The doors after installation.
The torsion rod springs make lifting the doors almost
||Using a can of expanding foam insulation, I
filled the gaps behind the steel extension and the rough stone
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.
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.
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