Video by UK Doors Online. This guide is based on the installation walkthrough by UK Doors Online, a Yorkshire-based aluminium door manufacturer, showing a complete sliding patio door installation from frame to finished seal. Their video is an honest, practical account from people who make and install these doors every day.
1. Measure the opening accurately
Measure the width and height of the structural opening at multiple points - top, middle, and bottom for width; left, centre, and right for height. Use the smallest measurement at each axis to determine the maximum door size. Openings are rarely perfectly square, so take nothing for granted.
Aluminium sliding doors are made to order in most cases. Double-check every measurement before you place the order - a door that arrives 10 mm too wide cannot simply be trimmed.
2. Remove the old door or frame
If you are replacing an existing door, remove it carefully. Take out the glass panels first if possible - sliding door glass is heavy and awkward, and you do not want it toppling. Then unscrew and pull out the old frame.
Check the reveal once the old frame is out. Remove any old sealant, screws, or fixings. The opening needs to be clean and sound before the new frame goes in. Patch any crumbling mortar or damaged brickwork at this stage rather than sealing over it.
3. Fit the sill and prepare the threshold
Most aluminium sliding doors come with a low-profile threshold sill. Fix this to the floor first, using the manufacturer’s anchors or appropriate fixings for your floor type. Get it perfectly level - a threshold that is even slightly out will cause the door panels to bind or roll unevenly.
If the floor level changes across the opening, pack and level it up before the sill goes down. A self-levelling compound over a small area is quicker than trying to shim the sill.
4. Install the outer frame
Lift the frame into the opening with a helper - aluminium door frames are not light, and trying to hold one straight while drilling is a recipe for it ending up crooked. Position it centrally in the reveal, check it is plumb on both uprights and level across the head, and pack with plastic frame packers as needed.
Fix the frame through the pre-drilled fixing holes into the surrounding masonry or timber frame using the correct fixings for the substrate. Expansion bolts for masonry; structural screws for timber. Check plumb and level again after each fixing - tightening one side can pull things out of true.
5. Hang the door panels
With the frame fixed and level, hang the sliding panels. The panels hook onto the top track first and then drop onto the bottom rollers. On most systems, tilt the panel at an angle to engage the top, then lower it vertically onto the bottom track.
The panels are heavy. Two people make this straightforward; one person doing it alone is struggling and risks dropping the glass or knocking the frame out of position. Do not attempt it solo.
6. Adjust the rollers and check the action
Once the panels are hanging, adjust the bottom rollers so the panel sits evenly in the frame and slides smoothly from end to end. Most systems have an adjustment screw at the base of the panel - turning it raises or lowers that corner of the panel on its roller.
The panel should slide with light, even pressure and land squarely against the seal at the closed end. If it is stiff on one side or gaps at the top, the rollers need more adjustment. Get this right before you move on - the handles and locks will not compensate for a panel that does not sit properly.
7. Fit the handles, locks, and weather seals
Fit the handle and locking mechanism per the manufacturer’s instructions. Test that the lock engages cleanly and that the handle returns properly. On multi-point locking systems, check that all locking points engage simultaneously when the handle is lifted.
Press the weather seals into the frame channels around the perimeter. These are usually a push-fit rubber or brush pile seal. They are what keeps draughts and rain out, so seat them fully and check there are no gaps at the corners.
8. Seal the frame to the reveal
Apply a continuous bead of exterior-grade silicone sealant around the outside of the frame where it meets the reveal. Smooth it off with a wet finger or a sealant tool for a neat finish. Do the same on the interior side.
That said, do not seal the weep holes at the bottom of the frame - these are intentional drainage points that let any water that gets past the seals out again. Block them and you trap water in the frame, which causes corrosion and staining over time.
When to call a handyman
Call Richard if the structural opening needs altering, the old frame has caused damage to the surrounding reveal, or the door is large enough that the glass panels are beyond safe two-person handling. Installing a sliding patio door is manageable for a careful DIYer, but the weight of the glass and the precision required on the frame make it one where having the right help makes the difference between a smooth job and an expensive problem.
Need a patio door fitted?
The Sandwich Handyman can help with door fitting, window repairs, and all kinds of property maintenance in Sandwich and the surrounding East Kent area.
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