Properly sized and supported sliding door headers bear the weight of the house, ensuring the good function of a sliding glass door.
A sliding door header is a rigid horizontal beam that sits directly over the door opening and bears the weight of the house so that there is no pressure on the door panels. The size of a sliding door header depends on the width of the building and how many floors are above the door. A correctly sized and installed sliding door header will ensure that the doors will open and close smoothly for the lifetime of the door.
How a Sliding Door Header Functions
Most wood frame house walls are constructed out of horizontal beams called plates that are supported every sixteen inches or so by vertical beams called studs. The rough opening for a sliding glass door is typically six feet wide. In a regular wall four studs would support the area below the opening. Instead, the header plate over the door must be strong enough to replace the studs by carrying the weight over the span of six feet without bowing.
How a Sliding Door Header is Constructed
The sliding door header is an integral part of the doorframe. They are typically fashioned out of 2x8s, 2x10s, or 2X12s that are doubled, tripled, or quadrupled with half inch plywood sandwiched in between for strength. The size of a sliding door header is determined by header tables, which take into account the weight of the building as well as possible snow loads.
The header sits on vertical jack studs, located on the left and to the right of the door opening, which form the door frame. Short vertical cripple studs placed every sixteen inches typically support the space between the ceiling plate and the header plate. The weight of the house is distributed evenly onto the header via the cripple studs, which carries the weight to the jack studs that likewise should be strong enough to bear the weight of the door opening.
Undersized Door Headers
Unfortunately, a common shortcut that sliding door installers use to save time and money is to use an undersized or insufficiently supported door header. Initially the door appears to be installed correctly. Over time the header will start to bow or one side will start to sink, putting pressure on the door itself.
The door will begin sticking, making it hard to open and close smoothly. Over time the crushing force of the weight of the house will take its toll. The weather stripping, the handle and even the glass will start to fail, leading to the premature replacement of even a quality sliding glass door.
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