Install an aluminium door frame plumb and square in an oversized opening, shim it, fasten it, seal the gaps, then hang and adjust the door.
For the full breakdown, see our best Aluminum Door Frame guide.
The real work in how to install an aluminium door frame happens before any fastening: the frame only fits as well as the hole it goes into. Measure the opening first, because one wrong dimension means a re-order at best and a binding, leaking door at worst. From there the routine is the same for patio sliders, French doors, bifolds, and storefront assemblies — measure, set plumb and square, shim, fasten, seal, hang.
Measure The Opening Before Anything Else
The opening decides everything, so check it before you remove an old door or order a new frame. Measure the width, height, and depth at several points — existing openings are rarely straight or level — and compare those numbers with the new frame’s stated dimensions. One installation guide stresses confirming the aperture actually fits the new frame before any teardown begins.
Equal diagonal measurements confirm the opening is square. If you’re still deciding which frame to buy, our tested aluminum door frame picks compare the top options before you commit to an opening size.
How Much Clearance Does An Aluminium Frame Need?
Plan for 10 mm to 15 mm of total clearance between the frame and the opening, with about 5 mm of that kept as a packing and expansion gap. Too little room and the frame can’t be shimmed square; too much and the sealant has nothing solid to grip. These are the numbers that matter at the fit stage:
| Clearance Or Fixing | Value To Work To | Why It Matters |
|---|---|---|
| Opening vs frame size | 10–15 mm total, roughly 5 mm packing and expansion gap | Room for shims and thermal movement without forcing the frame |
| Fixing spacing | 150 mm from each corner, 600 mm between fixings | Holds the frame true without bowing it |
| Lintel bearing | At least 150 mm onto brickwork on both sides | Keeps the frame supported and square in the opening |
| Diagonal check | Both diagonals equal | Confirms the frame is square before you fasten |
| Anchor tightening | Gradual, through pre-drilled holes only | Stops anchors twisting or bowing the frame |
Installing An Aluminium Door Frame: Fasten, Seal, Hang
Set the frame plumb, level, and square in the opening, then wedge packers behind every anchor point before a single fixing goes in. Slide shims or non-combustible blocking between the frame and the structure so the anchors don’t pull the frame out of true as they tighten. The jambs must sit vertical in both planes, with no twist or distortion.
Fasten through the frame’s pre-drilled holes using the manufacturer’s spacing — one residential guide calls for fixings 150 mm from each corner and 600 mm apart between. Tighten gradually and stop before the anchor cranks down hard: an over-tightened fixing bows the frame and jams the door later. Alumil’s technical guide for aluminium frame installation also requires the frame to sit under a lintel bearing at least 150 mm onto brickwork on both sides.
Seal the perimeter with caulk or silicone after the fixings are in, and bed any threshold in caulk to stop water tracking underneath. Only then install the door leaf and adjust the hinges so it swings freely with even gaps.
The job is done when the leaf swings without binding, the gaps read even from top to bottom, and the perimeter seal is unbroken. A door that fails any of those checks usually traces back to one step: a missing shim or an anchor tightened one turn too far.
FAQs
Do I need to leave an expansion gap with aluminium frames?
Yes. Aluminium expands and contracts with temperature, so the frame needs room to move — roughly 5 mm of packing and expansion space is typical, on top of the clearance needed for shims. Flexible caulk seals the gap without locking the frame rigid, so the joint stays weathertight as the metal moves.
Can one person install an aluminium door frame?
It is possible but rough. The frame has to stay plumb and square while you slide packers behind it, so a second pair of hands makes the job much easier. For larger patio, French, or storefront assemblies, two people are effectively required to lift and hold the frame without twisting it.
What happens if the frame is installed out of square?
The door leaf binds against the jamb, the gaps look uneven, and the lock may never line up. An out-of-square frame also strains the hinges and wears the door seals unevenly. Checking the diagonals and the level before fastening avoids all of it, which is why the measurement step comes first.
References & Sources
- Alumil. “Technical Guide for Aluminum Frames Installation.” Sets the fitting procedure, clearances, and lintel requirements for aluminium door frames.