Door Threshold / September 14, 2018 / Laure Lacharite.
Ive learned by the hard way of experience that its necessary to remove old existing jambs carefully. If directly fastened to masonry with cut nails jambs removal may break out the cinderblock unless the jambs are cut into short manageable lengths. An out of level concrete threshold step can be ground flat by a concrete cutting subcontractor or the door threshold can be adjusted by unscrewing and repositioning in the jamb by the amount out of level. Any attached brickmold and casing must be removed from the jambs to make installation easier with shimming. Also brickmold will probably have to be ripped in width to fit the overall brick opening width and height.
But what about retrofitting a new entry door system in an older home built with cinderblock masonry walls? You cant use the same technique of just nailing through the jambs the masonry will just deflect and bend a regular framing nail. Cut nails might possibly work but the chances for jambs alignment adjustments are slim to zero while the chances of masonry cracks or half-moon hammer head marks in the jambs are almost a given. Masonry screws need to be started in pre-drilled cinderblock holes which can be drilled through the jamb but Ive never been satisfied with their holding power alone where the cinderblock is prone to crumble around the holes while adjusting screws and snugging shims tight. Experience has taught me to always insert plastic expansion sleeves in the cinderblock to properly fasten masonry screws.
Several sill manufacturers provide plastic threshold protection that is specific to the model of sill they are selling. Unfortunately heavy duty plastic protectors are not available for every type of entry threshold so the protection is not easy to obtain. There is one surface protection company on the west coast that does inventory plastic threshold protection for two of the most common sill profiles. For protecting sliding door tracks there are two types of threshold protection. The first is a hinged plastic protection that flips over the tracks of sliding doors to keep them clean from debris.
Then re-assemble door system and re-shim into the indexed positions in the rough opening. At last now fasten jambs to the cinderblock with the masonry screws using shims at each screw location. Fine tune screw adjustments by wedging the shims to get the reveals around the door even. Adjust top and bottom jamb shims as necessary. Open and close door to check touching the weather stripping evenly top to bottom for any possible jambs twist. Some slight remaining jambs twist can be adjusted by persuading the jambs with a block and a hammer. Be careful. Now nail the shims permanently in position with a pneumatic nail gun shooting squarely into the cinderblock. Dont worry the nails should sink into the cinderblock as long as they are the proper length and are nailed squarely and firmly.