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Premium Fiberglass Doors – Performance

Gregg Hoyer illustrates the performance differences between a Therma-Tru Classic Craft and a Therma-Tru Fiber Classic including durability, function, and build quality.


Standard and premium fiberglass doors differ in design and in performance.  In this video, we’re going to be talking about performance.  Now here we’ve got a premium fiberglass door.  It’s got a three-quarter light, it’s got decorative glass, and it’s a beautiful door, but we want to understand what makes this so special, what makes it so different, and it’s performance.  So we’ve got that same door with parts cut away so that we can see inside the door and see what really makes it so special.

Now the top and the bottom rails on the Classic Craft door feature these large composite rails and they go from one edge of the door to the other.  They don’t allow any moisture through, and that’s moisture management.  We don’t want to get any moisture to the interior parts of the door because that will effect durability and performance.  Now we see the hollow areas of the door are filled with polyurethane foam, and that urethane foam give us great insulating value.

The Classic Craft door is a heavier door than standard fiberglass.  Why is weight important?  Well, in this case it means that it’s tougher, it’s more rigid, it’s more secure, it’s got more inside of it.  It also gives that real good feel of a solid wood door.  Now where does that weight come from?  Most of the weight comes from this part of the door.  This is the lock stile and the weight is in the beam that runs from the top of the door down to the bottom.  That beam is four and an eighth inches wide and it runs the entire length of the door.  It’s important for this part of the door to be very rigid, very secure, very stiff.  On the other side of the door in three points, we have hinges that hold the door in place.  But over here, a typical lock installation will run an area from about here to here.  The top and the bottom of the door can move, it can deflect.  That’s where we want that strength.  We want that part of the door to be very rigid so it doesn’t move.  In addition we want some extra material for very complex locking mechanisms.  Mortise locks or multi-point locks because we don’t want to compromise the strength of the stile in installing those kind of systems.

The Classic Craft skins are 50% thicker than standard fiberglass skins.  Why is that important?  Well, it give a lot of protection against impact.  Let’s say a lawn mower goes past the front of this door, or a rock comes flying out, hits the panel, or a baseball, or a golf ball – that thicker skin gives a lot of protection against cracking.  Classic Craft doors have fiberglass frames that hold the glass in place.  Now standard fiberglass doors will use plastic frames which is okay, but the fiberglass frames are more stable.  It’s also made out of the same material that the skin is made out of so it finishes very consistently.

Classic Craft doors have square wood edges just like wood doors.  Now the hinges are mortised to the edges of the door.  That’s really important for strength and for performance.  Some fiberglass door systems actually don’t mortise hinges to the edge of the door and that is a performance or a strength concern.  Also all Classic Craft hinges are ball bearing hinges and that gives you great durability, quiet operation, and peace of mind.

Classic Craft doors are architecturally correct.  That means the stiles, the rails, the components are in proportion, just like a wood door.  Keep in mind, Therma-Tru door systems are engineered door systems.  The door, the glass, the frames, the sills, the hinges, the weather strip, the multi-point locks all come from Therma-Tru and are tested as a unified system.  We feel this provides you with the very best performing fiberglass door unit.

Exterior Door, Fiberglass Door
Updated on March 7, 2019

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