Slimline Patio Doors

Slimline patio doors are available as bifolding doors, sliding doors, and slide and turn doors. There are also products with a frameless appearance for glass rooms and glazed extensions. This article explains the different minimalist and slim frame patio doors products making the most of glass.

Slimline patio doors explained.

The variety of slimline patio doors and other glazed products address the need for garden access doors but having significantly thinner sightlines than fully-framed sliding doors. At the same time, these doors provide all the functionality, security and weather performance. Even more important with slimline patio door is the requirement for a lower profile threshold.

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Slimline doors and windows

The design of slimline patio doors is based around creating products with the bare minimum of visible aluminium. Most products come designed from the outset as slim frame patio doors. Others rely on being fixed into the structure, effectively hiding the frame from view. As a result, the frameless style suits new extensions better than using these doors as a replacement for existing doors.

Three benefits of choosing slimline patio doors

Aside from a thin profile and ultra-slim look, slimline patio doors provide three additional benefits.

  • Better U-Values by using more glass
  • Larger glass panels than standard framed patio doors and more light as a result
  • Better and less cluttered views looking through closed doors

It is hard to find slimline patio doors in materials other than aluminium or steel.  The inherent strength of these two metals allows for thinner profiles than PVCu, timber or hybrid patio doors. 

Even the fully framed systems rely on some aluminium as it’s essential for the fixing of locks and other hardware as well as providing a fixing point to the building.

All these thin and sleek patio doors feature thermally insulated frames, a high quality construction and little compromise on security or weather performance with a well-designed system.

Understanding what defines a slimline patio doors product

slimline patio doors in a contemporary cheshire home
Reynaers Hi-Finity sliding doors by Altitude Aluminium.

There are no standards defining slim frame patio doors. Generally speaking, these doors range from sliding doors having slimmer door mullions, as well as specifically designed as a thinner system.

What constitutes slimline is also down to individual preference and satisfaction with the product. As a guide, we recommend this criterial as slimline:

  • Any mullion profiles below 30mm or no visible mullions at all.
  • Narrow frame and door profiles below 75mm
  • A low threshold or one flush with the inner floors and outside decking or slabs
  • Products designed for fixing into the building structure hiding the frame from view
  • Any specific window designed and obviously frameless.

Choosing slim frame patio doors products

slim frame patio doors in a new extension
Vistaline by ID Systems is a slide and turn slimline patio doors product

The following products are available as doors with reduced or minimal sightlines and work as patio doors for the home.

Understanding what’s a slimline bifolding door

The slimmest bifold at the door mullions is the Sieger Lux, structurally bonded bifold with 30mm sightlines.

Bifolding doors are evolving and today are thinner than before. Choosing a slimline bifold door product means finding those with the smallest sightlines at the closed and meeting doors. There’s a substantial choice of folding sliding doors and you can find out who makes the thinnest bifolds covering all the major brands.

How to get slimline French Doors

aluminium crittall style door in black in a traditional house
Black Alitherm aluminium steel-look door supplied by Newlite Home Improvements, Sussex

The most slimline of French doors remains any of the steel look products in aluminium. It’s possible to configure these without the bars giving a full glass appearance. Do bear in mind you won’t find a super slimline version of French Doors unless it’s single glazed.

One of the most popular is the Smart Systems Alitherm range, airMOD French doors and the Aluco Aluminium range.

How frameless products are some of the best slimline doors

ultra slim patio doors
Frameless slide and turn doors with no visible mullions made by FGC

Frameless doors are arguably the most impressive amongst slimline patio door.  First of all, these doors have no visible mullion. You only see aluminium with the perimeter frame and top and bottom of the door panels.

Remember with many of these systems, some are only intended for outside use or where there is little requirement for thermal performance or weather protection.  Many of these frameless slimline doors come as single glazed for internal use or outside, non-weathered installations.

One outstanding product designed as a fit-for-purpose external quality door is Frameless Glass Curtains.  These offer certified security, a weather rating, thermally insulated frames and are one of the best on the market.

There are many other products available however these use aluminium or plastic cappings to the glass edges.

Why Sliding doors come with the most options.

grey sunvista ultra-slim patio doors in a new home
Sunvista doors come with 19mm mullion and the option of a full frameless installation.

Slim frame patio doors are commonly associated with sliding doors. Any sliding door with a 20mm mullion is widely regarded as minimal and there are slimmer products available too. Some of the slimmer sliding doors include Sunvista, Vitrocsa, Cortizo, Ultraglide and many other brands. Here is a comprehensive section all about different sliding doors to help you understand the product.

Do not assume thin sliding doors only come as the more expensive structural glazed product.  There are the standard type of inline or lift and slide patio doors also having thin mullions.  A good example is the SUNFLEX SVG20 with a 20mm mullion, the Visoglide from Smart Systems, also with a 30mm mullion. YES Glazing provice a 24mm slider and the Cero Sliding door is one of the best made with 35mm mullions.  Therefore your choice of a slimline door may be down to cost as well as your desired aesthetic.

One thing sliding doors offering a slim solution in the home is the thin mullion. Any door below a 50mm sight line at the interlocking mullion is suitable. You can also check out our unique article showing you who makes the slimmest sliding patio doors to help you decide.


Slimline and minimal framed patio doors will vary depending on your project requirements, budget as well as your desired function from your doors. Bear in mind these door types are at the top end of the price range with higher manufacturing and installation charges too.

We can help with slim frame patio door product suggestions and putting you in touch with suppliers near you.