|Floor Clearance and Weatherproofing
|There are a number of alternatives to weatherproofing the bottom of the door, and the method used dictates the clearance required under the door. In this article I will describe the aluminium threshold, which is by far the more popular and effective method. The aluminium threshold is designed to fit onto the step or sill, under the door. It is trough shaped with either a brush or rubber draught strip incorporated. The front section is raised higher than the main body, so that when the door closes, and brushes over the draught strip to form a draught seal, the outside face of the door closes up to the raised front section.
Any rainwater running down the door that enters the trough can escape through small holes to the front section without traveling under the door. To minimise the volume of water entering the trough, a metal deflector should also be fitted onto the door, which serves to divert most of the water away.
Because aluminium thresholds have the manufactures fitting instructions, I can only generalise the fitting procedure.
Firstly, the bar should be cut the correct width, which is the width of the door frame, rebate to rebate, and before fitting, used to mark the clearance under the door. This is done by placing it on the floor, tight up to the inside of the closed door, so that a line can be drawn across the width of the door indicating the height of the bar from the floor. Because the front section is raised, the bar should be turned around so that the lower section that the door will pass over is used.
Remove the door and placed it outside face down on to the trestles and from the line that you have drawn, add to it the clearance required (as specified by the manufacturer) and draw a second line above it. The door should then be cut to this second line.
Before refitting the door, place the bar in position, so that the inside edge of the front raised section lines up to the rebate (This usually means notching out a small section from each side of the frame) and fix in position. Refit the door and ensure that it brushes over the draught strip as it closes, as well as closing up to and lining up to the raised front section when closed. Without removing the door, remove the bar and apply sealant such as silicone into the grooves to the underside of the bar and re-fix in position. All that now remains is to fit the deflector onto the door at a height that clears the threshold by a few millimetres.