Call Us
FREE SHIPPINGOn all orders
EXPERT FIT REVIEWEvery order reviewed before shipping
TRADE PROGRAMExclusive pricing for pros. Apply →
Get a Free Quote
Login

Country

Martin GD36B Fireplace Doors — Custom Exact-Fit Replacement

Martin GD36B Glass Doors: Repair the Kit, or Replace It Properly?

If you're searching "GD36B," odds are something on your fireplace doors just failed — a cracked pane, a bi-fold that won't track, a frame corner letting go. The Martin GD36B isn't a fireplace: it's the factory bi-fold glass door kit Martin Industries supplied for its SF36A and SF36AI 36-inch wood-burning zero-clearance fireboxes (the polished-brass version of the same kit was sold as the GD36PB). The model number lives on the door assembly itself, while the firebox behind it carries its own rating plate — usually on a side wall inside the firebox or up behind the top edge of the opening. Check both. Knowing you have a GD36B on an SF36A tells you exactly what your options are, and aren't.

Here's the short version of those options: Martin Industries went through bankruptcy in 2002 and its hearth assets changed hands, so the GD36B has been out of production for decades. Replacement glass and parts for it surface only sporadically — a scattered aftermarket parts listing here, a secondhand auction find there — a catch-as-catch-can supply for a door assembly that is itself decades old. You can chase a pane for aging hinges and worn bi-fold tracks, or you can replace the whole assembly with a door built new for your firebox. This page makes the case for the second route, honestly.

Why Patching a GD36B Rarely Ends Well

  • The glass is the symptom, not the disease. By the time a pane cracks, the kit's hinges, magnets or latches, gaskets, and fold tracks have taken decades of heat cycles. New glass in a fatigued frame buys you the next failure, not a fixed door.
  • Supply is a coin flip. Those listings are one-off finds. If a second pane goes next season — bi-folds break in pairs more often than you'd think — there may be nothing on the market at all.
  • Fitment risk cuts both ways. Used and surplus panels come with no guarantee they match your kit's revision, and a bi-fold panel that's slightly off binds in the track or leaves a gap at the center meeting point.

None of this means your fireplace is done. The SF36A/SF36AI firebox behind the doors is typically sound — it's the bolt-on kit that aged out. Fireboxes and doors have different lifespans; you replace the door, not the fireplace.

The Durable Fix: A New Door Built for the SF36A/SF36AI

ExceptionalFire builds complete replacement doors for discontinued prefab fireplaces, including the Martin firebox family the GD36B was designed to cover. Instead of hunting parts for a discontinued kit, you get a new assembly made for your exact opening:

  • Confirm what's behind the doors. Take a photo of the fireplace — doors on or off — and upload it to our AI Fireplace Expert. It identifies the firebox from the face and frame style even if both the kit label and the rating plate are gone.
  • Measure the opening, not the old door. With the GD36B removed (or its frame edges accounted for), measure the firebox opening itself: width at top, middle, and bottom; height at left, center, and right; smallest number wins in each direction. Old door frames hide the true opening, so don't transcribe the kit's dimensions — our measuring guide shows exactly where the tape goes. For this model, measuring is not optional; we don't build from the kit number.
  • Configure it and see the price immediately. The configurator on our prefab fireplace door collection takes your numbers and your finish, glass, mesh, and handle choices, and prices the door on the spot.
  • Built and installed without drama. Every door is fabricated to your measurements to the 1/8 inch, glazed with tempered safety glass, and framed inside-fit for zero-clearance fireboxes. It mounts with basic hand tools, the same way the factory kit came off.

Mistakes That Make a Broken GD36B Worse

  • Burning with the glass closed. The GD36B used tempered glass, and so do standard replacement doors. Tempered glass can't take sustained direct flame — burn with doors fully open, close them only after the fire is out.
  • Keeping a cracked pane in service. Damaged tempered glass can let go suddenly. Remove the broken panel or keep the fireplace cold until the door is dealt with.
  • Cutting ordinary window glass to fit. Annealed glass shatters dangerously under fireplace heat. Only tempered safety glass belongs in a fireplace door.
  • Swapping in an overlap masonry door. The SF36A/SF36AI is a prefab firebox with a sheet-metal face — it needs an inside-fit door, not one that clamps to surrounding brick.
  • Ordering a new door from the GD36B's frame dimensions. The kit's outer frame isn't your firebox opening. Measure the opening itself with the old assembly out of the way.

Frequently Asked Questions

What size fireplace doors fit a Martin GD36B?
The GD36B is the door kit, not the fireplace — it fits Martin's SF36A/SF36AI 36-inch fireboxes. A replacement door is sized to that firebox's measured opening, which varies by installation, so measure the opening directly and we'll build the door to those exact numbers.

Can I still buy replacement glass for the GD36B?
Only sporadically — the odd aftermarket parts listing or secondhand find, with no steady supply since Martin's 2002 bankruptcy ended factory production. Given the age of the surrounding hardware, a complete new door built for the firebox is the more durable repair.

Is it safe to close the new glass doors while the fire burns?
No — the same rule that applied to your factory kit still applies. Tempered glass doors stay fully open during the burn and close after the fire dies down, where they stop heated room air from escaping up the flue.

Do I have to get bi-fold doors again?
No. Because your replacement is built to order, you choose the door style, finish, glass, and handles in the configurator rather than being locked to the original bi-fold pattern. If you're unsure what suits the SF36A opening, our specialists are available seven days a week to talk it through.

Retire the Kit, Keep the Fireplace

Pull out the tape, follow the measuring guide, and price a new door for your SF36A or SF36AI in minutes on the prefab fireplace door collection. Not certain what firebox is behind that failing GD36B? A single photo in the AI Fireplace Expert settles it — and our specialists are on hand to make sure the door you order is the last one this fireplace needs.

Have a different Martin firebox in the house? We also cover the Martin SF36, Martin SF42, Martin SI36, Martin SA36, Martin SC36, Martin SC42, Martin SA42, Martin BE42, and Martin SB4800.