Classic Series
Steel doors for flat, level foundations. Sizes O, B, C and SL; primed and select powder-coated options.
YOUR SUPPLY PARTNER FROM THE GROUND DOWN™
YOUR SUPPLY PARTNER
FROM THE GROUND DOWN™
Basement Door Installation Resource
Choose and Install the Right BILCO Basement Door
Measure your opening correctly, compare BILCO door types and sizes, and follow instructions written for your exact door family.
Do not order from the label or assumed size of your old door. Measure the exposed foundation itself after the old door is removed.
Start Here
One Brand, Three Different Door Systems
The correct door depends first on the shape and condition of your foundation. These systems are not interchangeable.
Type BR
Steel doors for existing, structurally sound sloped masonry sidewalls. Models BR-1, BR-2 and BR-3.
Ultra Series
Corrosion-resistant polyethylene door for a flat foundation. Available in one Size C with its own instructions.
Check the masonry first. Loose, crumbling or unsuitable sidewalls must be repaired or rebuilt before a new door is anchored.
Most Important Step
Measure Before You Buy
Remove the old door and measure the exposed foundation in inches. Masonry may have been repaired, widened, capped or altered since the old door was installed.
Flat-foundation measurements for Classic and Ultra doors.
The five measurements
- W1 — inside width: clear opening between the inside faces of the sidewalls.
- W2 — outside width: overall width across the outside edges of both walls.
- L1 — inside length: clear stairwell length from the house to the inside of the front wall.
- L2 — outside length: full foundation length from the house to the outside of the front wall.
- H1 — height: from the flat mounting surface to the top of the house-wall opening.
Expose the foundation
Remove the old door, old frame and loose material. Measure the foundation—not the old frame.
Measure W1
Check near the house, in the middle and near the sill. Record the largest clear inside width the frame must cover.
Measure W2
Check more than one location and record the smallest usable outside width so the frame stays fully supported.
Measure L1 and L2
Measure both sides if the areaway is not square. Record the inside opening length and the full outside foundation length.
Measure H1
For a flat foundation, measure from the frame mounting surface to the top of the wall opening. Type BR selection uses the slope and width/length measurements instead.
Measure only to sound, usable foundation material. Loose brick, crumbling concrete and unsupported voids are not safe mounting surfaces.
Flat-foundation selection rule: Classic or Ultra
- Width: door width must be at least 4 inches greater than W1, but no greater than W2.
- Length: door length must be at least 2 inches greater than L1, but no greater than L2.
- Height: door height must be greater than H1.
| Door | Width | Length | Height | Extensions |
|---|---|---|---|---|
| Classic O | 47 in. | 58 in. | 30 in. | None |
| Classic B | 51 in. | 64 in. | 22 in. | None |
| Classic C | 55 in. | 72 in. | 19-1/2 in. | Classic C only |
| Classic SL | 51 in. | 43-1/4 in. | 52 in. | None |
| Ultra C | 56 in. | 73 in. | 19-1/2 in. | Ultra only |
Example: W1 46, W2 52, L1 61, L2 66 and H1 20 inches fits Classic Size B: 51 inches wide, 64 inches long and 22 inches high.
Sloped Sidewalls
Type BR selection
Use Type BR only on two structurally sound, flat sloped masonry walls that are level with each other, can hold anchors and allow the sill to sit 2–4 inches above grade.
- Door inside width must be equal to or greater than W1, and overall width must be less than W2.
- Door length must be at least L1 + 2 inches, but no greater than L2.
| Model | Inside width | Overall width | Inside length | Overall length |
|---|---|---|---|---|
| BR-1 | 36 in. | 43-3/16 in. | 58 in. | 65-1/8 in. |
| BR-2 | 40 in. | 47-3/16 in. | 60-1/4 in. | 67-5/8 in. |
| BR-3 | 44 in. | 51-3/16 in. | 67-3/8 in. | 74-1/2 in. |
Need Help Choosing?
Send us W1, W2, L1, L2 and H1, plus: a straight-on house-wall photo; an overhead stairwell photo; both full sidewalls; the sill and surrounding grade; close-ups of damage or voids; and tape-measure photos of every critical dimension.
Contact Basement Supply Before OrderingModel Comparison
Classic, Type BR or Ultra?
| Feature | Classic | Type BR | Ultra |
|---|---|---|---|
| Foundation | Flat, level | Sloped masonry | Flat, level |
| Material | Steel | Steel | Polyethylene |
| Sizes | O, B, C, SL | BR-1, BR-2, BR-3 | Size C only |
| Lift hardware | Gas springs; model hardware supplied | Gas springs plus adjustable coil springs | Motion dampers |
| Finishing | Primed or powder-coated | Primed or powder-coated | Do not paint |
Primed steel: finish within 45 days with exterior alkyd-base enamel—one thin coat, then a second coat on exterior and interior primed surfaces. Powder-coated steel: no additional finish painting is required.
Longer Openings
Use Only the Extension Made for Your Door
An extension adds length at the house end. It cannot correct a width, height or foundation-type problem.
Classic Size C
6, 12, 18, 24 and 30 inches. Total lengths: 78, 84, 90, 96 and 102 inches. Choose a total at least L1 + 2 but no longer than L2. Multiple extensions are supported only with BILCO’s documented support and weatherproofing.
Type BR
6, 12 and 18 inches, matched to BR-1, BR-2 or BR-3. The panel overlaps the header by at least 1 inch. Multiple panels may overlap; confirm support and flashing before ordering.
Ultra
6- and 12-inch polyethylene extensions. Total length is 79 or 85 inches with one panel. BILCO permits no more than two Ultra extensions; confirm a two-panel layout before ordering.
Create a Suitable Mounting Surface
Foundation Plates
Foundation plates can cover rough masonry and minor voids, reduce an oversized inside width, and support certain corner installations. They do not make weak masonry strong.
| Model | Width | Length | Height |
|---|---|---|---|
| FP5 | 5 in. | 84 in. | 1-3/4 in. |
| FP8 | 8 in. | 84 in. | 1-3/4 in. |
| FP11 | 11 in. | 84 in. | 1-3/4 in. |
| FP14 | 14 in. | 84 in. | 1-3/4 in. |
How to choose
- Measure the top width of each sidewall.
- Calculate how much W1 must be reduced for the selected door.
- Choose plates wide enough to cover the wall and create the needed inward overhang.
- Confirm the plates and door can anchor into sound, level masonry.
If overhang exceeds 6 inches, BILCO requires continuous support underneath. For areaways longer than 84 inches, follow the official sheet for overlapping a cut second plate.
Repair first: loose brick, crumbling mortar, movement, major cracks and large missing areas must be repaired or recapped—not hidden beneath plates.
Inspect, Plan, Protect
Before Installation
Confirm the site
- Correct family, model, finish and extension
- Sound, clean, dry, correctly sized foundation
- Frame can rest fully on top—never buried in concrete
- Water drains away; roof runoff is controlled
- Interior door at the bottom of the steps
- Current instructions and local code requirements checked
Typical tools
- Tape, pencil and level
- Drill and manual-specified bits
- Screwdrivers, wrenches and sockets
- Exterior sealant specified by the manual
- Correct wall fasteners where not supplied
- Safe stair or ladder access
Safety equipment
- Work gloves and safety glasses
- Hearing protection when drilling
- A second capable person for heavy leaves
- A secure guard around the open stairwell
Safety: Keep people away during installation. Close and lock the doors when the areaway is not in use. Never stand, sit or place loads on the doors.
Flat Foundation — Steel
Classic Sizes O, B, C and SL
Use the manual packed with your door for every hardware count, drill size and anchor location.
1. Prepare and assemble the frame
Remove the old door, patch holes and repair damaged masonry. Attach the header and sill to the side pieces with supplied bolts and caulk header seams. Size SL: orient the sill mounting tabs exactly as shown in the official detail.
2. Position, square, drill and anchor
Set the frame flush to the house, plumb both sides and make diagonal measurements equal. Mark and drill per the manual. Anchor the frame to masonry and use wall-appropriate fasteners for the house flanges. Caulk the exterior perimeter with opaque exterior polyurethane—never mortar.
3. Install leaves and lift hardware
Use two people as needed. Install hinge and cotter pins, then attach lift hardware only after the frame is secure. On the current gas-spring arrangement, the larger-diameter portion is on top. Use the exact hardware supplied with your model.
4. Finish and test
Finish primed steel within 45 days; powder-coated doors need no added paint. Open and close slowly. Confirm smooth control, complete closure, secure fasteners, continuous caulk and clear header drainage.
Sloped Masonry Sidewalls — Steel
Type BR-1, BR-2 and BR-3
Type BR is not a Classic frame placed on a slope. Its frame, anchoring, lift assistance and flashing are different.
1. Inspect the walls
Both sloped sidewalls must be sound, flat, level and level with each other. The sill must sit 2–4 inches above grade. Repair or reinforce weak masonry first.
2. Assemble, square and anchor
Attach the sill, set the supported side pieces and header, equalize both diagonals and tighten. Apply silicone beneath the frame on clean, dry masonry. Drill and install the supplied anchors exactly as specified; caulk anchor holes and header seams. Never bury the frame in concrete.
3. Install the leaves
The leaves can slam before lift assistance is installed. Slide hinge pins fully into their brackets and secure them with cotter pins while controlling each leaf.
4. Install gas and coil springs
Follow the BR-specific orientation; the exposed spring portion is at the bottom on the current arrangement. Add the supplied supplemental coil springs as needed for controlled operation on the installed slope.
5. Adjust the supplemental springs
Use only the number and placement of coil springs needed for controlled operation on the installed slope. Test carefully and keep hands clear of moving parts.
6. Finish, flash and test
Finish primed steel within 45 days. Install the aluminum flashing at the house with appropriate wall fasteners; replace siding over it or seal its top edge on masonry. Confirm full closure, proper drainage and a clear header channel.
Flat Foundation — Polyethylene
Ultra Series Size C
Ultra uses its own polyethylene frame, anchors, hinges and motion dampers. Do not use Classic steel-door hardware or steps.
1. Prepare and assemble
Confirm a smooth, level foundation. Connect the header and side panels with supplied drive screws, then connect the aluminum sill with the exact screws, nylon spacers and washers shown in the Ultra manual.
2. Position, square and anchor
Plumb the sides and make diagonal measurements equal. The distance between side-piece anchor holes must be at least 53-1/4 inches on center. Drill, anchor and fasten the header as specified, then caulk the full exterior perimeter with opaque polyurethane.
3. Attach leaves and dampers
Fasten each closed leaf to its hinges in the manual’s order. Install ball studs facing the house and snap each motion damper onto the upper and lower studs.
4. Inserts, care and final check
Follow the separate directions for solid, vented or clear inserts. Do not paint Ultra. Clean with a non-abrasive household cleaner. Confirm aligned leaves, free drainage, continuous caulk and smooth movement.
Ultra does not use: Classic C steel extensions, BR extensions, Classic gas springs, steel-door paint instructions or the BILCO Weather Strip Kit.
Official Ultra Instructions
Get the Details Right
Common Mistakes to Avoid
Measuring
- Ordering from the old label
- Measuring only once
- Confusing inside and outside dimensions
- Measuring to damaged material
- Using an extension to fix width or height
Installation
- Starting with an unsquare frame
- Anchoring into weak masonry
- Burying frame parts in concrete
- Skipping required caulk or flashing
- Operating leaves before lift hardware
Stop and get help
- Masonry moves or crumbles
- The areaway must be rebuilt
- The wall needs structural alteration
- A custom multi-extension support cannot be verified
- Safe lifting or fall protection is not possible
Official BILCO Videos
Watch BILCO Door Installation
Time-Lapse Installation
See the overall sequence of a BILCO basement-door installation.
Watch on YouTube →
Detailed Door Installation
Watch a BILCO door installation using foundation plates to improve the areaway.
Watch on YouTube →In-Depth Installer Training
Need a More Detailed Walkthrough?
For a thorough step-by-step breakdown of installing a Classic Series basement door, watch BILCO's detailed installer-training video.
Watch the In-Depth Installation Video →Video scope: These videos mainly show Classic/general installation. Type BR and Ultra installers must follow their separate model-specific manuals.
Shop Basement Supply
Doors and Accessories
Classic Series
Primed steel doors
Powder-coated doors
Primed Size C extensions
Powder-coated Size C extensions
Type BR
Primed BR doors
Powder-coated BR doors
Primed BR extensions
Powder-coated BR extensions
Ultra Series
Ultra polyethylene door
Ultra extensions
Foundation Plates
Primed foundation plates
Powder-coated foundation plates
Quick Answers
Frequently Asked Questions
Can I order the size shown on my old BILCO label?
No. Remove the old door and measure W1, W2, L1, L2 and—on flat foundations—H1. Repairs and older construction can change the usable opening.
What is the difference between W1 and W2?
W1 is the clear inside opening. W2 is the full outside width across both walls. The frame must cover W1 while resting on enough sound foundation within W2.
Should I choose Classic, Type BR or Ultra?
Classic and Ultra fit flat foundations. Type BR fits two existing, sound sloped masonry sidewalls. Each system has separate hardware and instructions.
Are Classic C and Ultra C the same size?
No. Classic C is 55 × 72 × 19-1/2 inches; Ultra is 56 × 73 × 19-1/2 inches. Their extensions and hardware are also different.
Can I combine extensions?
BILCO documents multiple Classic C and overlapping BR extensions when properly supported. Ultra permits no more than two. Never combine extension families.
Can foundation plates cover damaged masonry?
They can cover rough surfaces and minor voids, not structural damage. Loose, unstable or crumbling masonry must be repaired or recapped.
Do primed steel doors need paint?
Yes. Finish within 45 days using exterior alkyd-base enamel: one thin coat followed by a second coat on both exterior and interior primed surfaces.
Can I paint an Ultra door?
No. BILCO states that the high-density polyethylene door cannot be painted.
Does this cover the Weather Strip or Keyed Lock Kits?
No. Those accessories use separate instructions and are intentionally outside this guide. The Weather Strip Kit does not apply to Ultra.
Official manuals and sizing sheets
Measure Twice. Order Once.
Still Unsure Which BILCO Door Fits?
Send us your five measurements and photos before ordering. We can help identify the correct family, size, extension and foundation-plate setup.