How To – Installing a Sliding Glass Door

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    There are 2 difficult parts of installing an exterior sliding glass or pre-hung french door set.

    The first and most important is that you will probably need help to position the door in the opening. Although you can probably get the delivery people to place the door near the opening when they drop it off if you bribe them or if the company provides that service the weight of the door is pretty much over the limit of one person. In a pinch you may be able to install it by yourself but it won’t be easy. Two or even four people is a better situation.

    The Second is actually getting the door frame and panels into the door opening without ruining your caulking. It may not sound important but if you can’t lift the frame easily into place you will ruin your caulk and then you will have a door that leaks during a rainstorm. Its not that a door frame is very heavy its that it is difficult to handle because it is so wide. so you are probably going to either need long arms or a friend for this part.

    So, now that you have planned for the weight and bulk of the door and bribed a friend with pizza to help you can start preparing the opening to accept the new door.

    All exterior doors are installed from the outside of the house.

    If you have a pre-hung door it will come with directions and you should refer to the manufacturers recommendations. But lets step through the common steps that you will have to take on an average door.


    Preparing your door opening
    If you are installing a new door in a nonexistent opening. Meaning you will need to cut into the walls and the siding on the exterior of the house then you will most likely need a permit. You will need to install a Header above the door opening to support the load. This is not a difficult job but it will require that you calculate the loads of the upper floor and submit a sketch plan to your permit office.

    If you are replacing an existing door then your opening should be plumb and square unless the home has settled.

    Use a framing square in all four the corners of the door and quickly check for out of square.

    If there is a problem then you should use a 4 foot carpenters level to check for plumb and level on the sides and top and bottom of the opening.

    Take the proper measurements as instructed by the manufacture. Openings should be about a quarter to a half inch larger on the top and sides of the door to allow for shimming.

    Inspect the decking where the bottom of the door will sit. If you see any dry or wet rot then you should make repairs before continuing. If the studs on either side of the opening seem weak then you can install a second stud. Use construction adhesive and nail on an angle to provide for good connections.

    Caulk before you install

    Lay the frame directly in front of the opening if needed assemble the door frame following proper caulking instructions.

    Never skimp on the quality or amount of caulk that you apply to the door frame. Doing so can result in leaks that are not easy to fix. It is always better to apply too much caulk then too little.


    Now apply a few good passes of silicon caulk to the bottom plate of the door frame and to the nailing flanges. If the decking / flooring that will accept the door is OSB you must be careful to over caulk the bottom plate because OSB is not smooth and will not take form a good bond.
    Also if the sheathing on the house is OSB you should apply a few passes of caulk on both the flange nailer and directly to the OSB. This will improve your chances of a good seal.

    Positioning the frame in the opening
    This is where you really can use a helper. You must install the frame in the opening so that you do not disturb the caulk that you just applied. Lean the top of the frame out away from the house and lower the frame onto the decking without pushing the bottom plate towards the house.

    Now complete the install by leaning the top of the door frame into the opening. You should see extra caulk coming through prepunched nail holes and out from under the flange. If not you probably didn’t use enough caulk.

    Install one nail in the nailing flange on the top right side of the frame and check your plumb and square of the frame with a level.


    Now install the next nail in the lower left side of the frame and check that side for plumb and level.


    You can now begin nailing the flange around the door and continuously check for plumb and square.

    You can now install the door panels.

    Begin with the moving door first.
    Follow instructions on how to attach the wheels to your door if you will be positioning the moving door on the opposite side then delivered.

    Once the moving door is on its track slide it across the frame to each side of the opening until there is a small gap of about 1/8 th inch gap between the door and the side of the frame. Make sure this gap is uniform all the way up and down the door opening this will prove that the door frame is square and plumb. If the gap between the door and the frame has a bow then you will have to make adjustments and shim if necessary.

    Once you are happy with the gap and the square of the frame you should install the door locking mechanism and the handle. The mortise is inserted in a pre made hole that may be covered with a plastic plate. Check your instructions but you should be able to knock the plastic plate out with a chisel pretty easily.

    Now Lock your moving door into the frame so it won’t move.

    The Fixed Door is inserted last and from the outside of the house.
    Follow the manufactures instructions on how you should insert clips or screws to secure the fixed door in place.

    If you are installing a french door type system then you will have the option of making one door fixed or both doors operable. Additional instructions will be required from the manufacture as to how to check the gap and weatherstripping.

    Once the doors are installed you will have the ability to make fine adjustments by turning alignment screws usually found at the bottom of the door.

    Now that the door is installed you should allow 24 to 48 hours for the caulk to cure before you use the door extensively. If you have to use the door this is fine but remember that as the caulk cures it will form the weatherstripping that will prevent later problems so it is best to wait a few days before you give the door any heavy use.

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