Superior RD-42 Fireplace Doors — Custom Exact-Fit Replacement
Replacement Glass Doors for the Superior RD-42 Wood-Burning Fireplace
If your home has a builder-grade fireplace from the 1980s or 1990s, there is a good chance it is a Superior RD-42 — a nominal 42-inch, wood-burning, zero-clearance (prefab) firebox that was installed in enormous numbers across the U.S. It is the larger sibling of the popular RD-36, and like most fireplaces of its era, the glass doors it originally shipped with (or was designed to accept) have long since been discontinued. The good news: you can still get doors that fit it perfectly — they just have to be built for your fireplace, not pulled off a shelf.
Step 1: Confirm You Actually Have an RD-42
Never order fireplace doors from memory or from a house listing. Every prefab fireplace carries a metal rating plate (also called a data tag) stamped with the exact model number. On Superior fireboxes you will typically find it inside the firebox itself — usually along the side wall or floor near the opening — or tucked behind the bottom louvers on the face of the unit. Open the mesh screen, shine a flashlight, and look for a small metallic label.
One important wrinkle: Superior was later folded into Lennox Hearth Products, so your plate may read "Superior," "Superior Fireplace Company," or "Lennox" — the RD-42 appears under both brand names in factory documentation. Related Superior/Lennox models from the same family include the BR-42, BC-42, HC-42, BBV-42, and B40; several of these share door hardware, which is why replacement listings often group them together. If your plate shows any of these, you are in the right place.
Why You Can't Just Buy the Original Doors
Superior stopped producing the RD-42 and its factory door kits decades ago, and the OEM accessories were discontinued along with the firebox. Surviving new-old-stock kits are essentially gone, and used doors are a gamble — warped frames, missing tracks, and tempered glass of unknown history.
The tempting shortcut is a universal or "masonry-style" door from a big-box store, and it is the single most common mistake we see. Masonry doors are designed to overlap a flat brick face and anchor into mortar joints. A prefab fireplace like the RD-42 has a sheet-metal face, precise factory dimensions, and strict listing requirements. A universal door will not seal against the metal face, usually cannot be anchored safely, can block cooling louvers, and installing an unlisted door on a zero-clearance firebox can violate the unit's certification and your insurance terms. Prefab fireplaces need an inside-fit door made for prefab fireboxes — a frame sized to slip into the opening and attach the way the manufacturer intended.
Our Solution: Custom Doors Built to the 1/8"
ExceptionalFire builds replacement doors specifically for prefabricated fireplaces like the Superior RD-42. Instead of forcing your fireplace into a stock size, we manufacture each door to your measured opening, accurate to the eighth of an inch. You choose the frame finish, door style, and handle options, and the finished unit arrives ready to install with basic hand tools — no masonry anchors, no grinding, no guesswork.
Not sure what you are looking at? Snap a photo of your fireplace and let our AI Fireplace Expert match it — it takes about 15 seconds and works even when the rating plate is dirty or painted over. Once you know your model, you can configure your door and see your price instantly in our prefab door collection. No waiting for a callback, no "request a quote" black hole.
Measuring Your RD-42 Opening
Because we build to your exact opening rather than a catalog size, careful measurement matters more than the model number itself. You will need the opening width (measured at top, middle, and bottom), the opening height (left, center, right), and a quick check of the surrounding face. Our step-by-step measuring guide walks you through it with photos, and takes about five minutes with a tape measure. If two measurements disagree, send us both — that is exactly the kind of detail custom manufacturing absorbs and universal doors cannot.
Safety First: How Glass Doors on a Prefab Fireplace Should Be Used
Glass doors on a wood-burning, zero-clearance fireplace like the RD-42 are meant to be open while the fire is burning. Closing bi-fold glass doors on an active wood fire traps heat inside a firebox that was never designed for it, which can overheat the unit and damage the glass and surround. The doors earn their keep when the fire dies down: close them to stop room air from escaping up the flue overnight, to keep smoke and stray embers in check as the fire smolders, and to block cold drafts and pests in the off-season. Always keep the mesh screen closed during the burn, and follow the instructions supplied with your fireplace and your new doors.
Frequently Asked Questions
My rating plate says Lennox RD-42, not Superior. Is that the same fireplace?
Yes. Superior became part of Lennox Hearth Products, and the RD-42 appears under both names in factory literature. The firebox and door requirements are the same — order using your measured opening and you are covered.
What if the rating plate on my fireplace is missing or unreadable?
It happens constantly on 30-year-old units. Take a straight-on photo of the fireplace and run it through our AI Fireplace Expert, or measure the opening using our guide — because every door we build is made to your dimensions, a missing tag does not stop the order.
Will new glass doors stop the cold draft coming from my RD-42 in winter?
That draft is one of the biggest hidden energy costs of an older prefab fireplace: warm room air escapes up the flue around a loose damper. A properly fitted, gasketed glass door dramatically reduces that air loss when the fireplace is not in use.
Can I install the doors myself, or do I need a technician?
Most customers install our inside-fit prefab doors themselves in under 30 minutes with a screwdriver and a drill. Each door ships with model-appropriate hardware and instructions, and our team is available if you get stuck mid-install.
Get Doors That Fit Your RD-42 the First Time
Configure your Superior RD-42 replacement doors online in minutes and see your price instantly — or, if you would rather talk it through, our fireplace experts are available 7 days a week by phone, chat, or email. Measure once, order once, and give a 30-year-old fireplace a door that looks like it came from the factory.