What you are really buying when you buy an aluminium pergola
Aluminium took over the pergola market for unglamorous reasons. It does not rot, it does not need a coat of stain every other spring, and it can carry a wide span on a slim section, which is what people mean when they say a structure looks modern. What it does not do is standardise the market. Two aluminium pergolas of the same footprint can be built very differently, and the difference shows up in the fourth or fifth winter rather than on the day it is installed.
Extrusion, not tube
Quality aluminium structures are extruded profiles with internal chambers, not folded sheet or plain box tube. Those chambers are where the rainwater channels, the wiring runs and the fixings land, which is why a good frame looks clean from underneath with no visible cables or brackets. When you compare quotes, ask what the post and beam sections are and whether water is carried inside the frame or by an add on gutter.
Powder coating and the RAL question
Aluminium is finished with a polyester powder coat baked onto a pre treated surface. Standard choices are anthracite grey, white and black, and most systems will do any RAL shade to order. The finish matters more near the coast or in an exposed rural spot, where salt and grit find any weakness in preparation. A well coated frame needs washing, not repainting, and that is the main practical reason people move away from timber.
- Anthracite grey suits grey render, slate and modern glazing
- Black reads sharper against red brick and pale patios
- White brightens shaded north facing gardens but shows algae sooner
- Custom RAL usually adds lead time rather than a large cost
Span, posts and why the middle post appears
The wider you go between posts, the deeper the front beam has to be to carry snow and wind load without deflecting. There is a point on every system where a fourth post has to appear, and a supplier who avoids mentioning it is either using a heavier beam, or they are hoping you will not notice the sag in year three. Ask what the maximum clear span is for the specific beam being quoted rather than for the range in general.
Engineering is not an upsell. A frame that is quietly underspecified for a windy Yorkshire garden costs more to put right than it saved.
Bring us the two quotes you are comparing
We will tell you plainly what each frame is doing structurally, what it is not, and what your garden actually needs across a Yorkshire winter.
Fixed roof or louvred roof on the same frame
Most aluminium systems can take either a fixed glass roof or motorised louvre blades. The frame looks similar, but the louvred version carries a motor, a drive shaft and blade bearings, and it needs a slightly different structural allowance because the load path changes when the blades close. If you like the aluminium look but want the light in permanently, the fixed glass version is simpler and there is nothing to service.
What lives inside a modern frame
The reason people accept aluminium over timber is usually integration. LED strips sit in the beam channel, zip screens track inside the posts, heaters bolt to purpose made rails, and the whole lot runs from one supply. Deciding on these at survey is cheap. Adding them after the frame is up means surface trunking, which spoils the exact clean look you paid for.
- Dimmable LED lines in the beam recess
- Infrared heaters on the crossbeam rather than clipped to a post
- Zip screens running in the post track for wind resistance
- One switched supply with the cabling hidden inside the frame
Maintenance, honestly
Twice a year, wash the frame with warm soapy water, clear the gutter channel and check the post bases for standing debris. That is it for the aluminium itself. If there are louvres, the blade bearings and the motor should be looked over at the same time, and if there are screens, the tracks want brushing out. Nothing here needs a specialist, and nothing needs painting.
Questions people ask us about this
Does aluminium get too hot to touch in summer?
The frame warms in direct sun like any metal, but the profiles are thin walled and shaded by their own roof for most of the day, so it is rarely an issue in a British garden.
Will an aluminium pergola dent?
Structural extrusions are far stiffer than the thin sheet used on cheap flat pack gazebos. Careless ladder work can mark a post, but normal garden use will not.
Is aluminium noisier in rain than timber?
A fixed glass roof and a closed louvred roof both make some sound in heavy rain. Laminated glass has an interlayer that dampens it noticeably, which is worth specifying if the structure sits outside a bedroom window.
Can the colour be changed later?
Not easily and not well. Powder coating is a factory process, so choose the finish carefully at order stage rather than planning to change it.
How does the warranty work on an aluminium structure?
Frames are covered up to 10 years, with motors, glass and electrical components carrying their own manufacturer terms.
In short
Aluminium wins on lifespan and integration rather than looks alone. Read the beam sections, the span limits and how water leaves the frame, and the better quote becomes obvious.