The choice of material for window and door frames not only has implications on the cost of your build, but its overall look and functionality. 


  Kloeber Aluminium KustomSlide Mono and Plus on large new build home - grand designs

Image: Aluminium KustomSlide sliding doors, Kloeber

One of the largest purchases you will make in a self‐build or renovation project will be your doors and windows. From house design to security and energy efficiency there is a lot more to making your frame material choice than you may have first thought.

The 4 main material types used to fabricate doors and windows are plastic, timber, aluminium and alu‐clad (or composite, which is more than one material type used together, usually with timber internally an aluminium cladding on the outer face). The Grand Designs magazine team asked the bespoke glazing experts at Kloeber to explain the pros and cons of each of these options.

Plastic frames

Plastic units are cost effective and normally available on short lead times but they are prone to expansion, contraction and warping with climatic change. The frames tend to be thick with a restricted selection of colour options, they also lack in strength therefore cannot support large panes of glass. Some people do not like the aesthetics of plastic doors or windows and feel they are less suited to period properties, however they will appeal to those whose budget is a key consideration.

Timber frames

kloeber timber flush casement windows on extension - grand design

Image: Flush timber casement windows, Kloeber 

Timber is a naturally insulating material that keeps the heat in and the cold out. It’s also the sustainable, eco‐friendly choice if sourced responsibly (use FSC certified timber). Low U‐values and greater energy efficiency makes timber perfect for new builds and eco homes. Look for engineered timber, this is a term used to describe the manufacturing process where smaller strips of solid timber are laminated and glued together to form the larger segments that are then cut to size. This results in a more durable and stable timber that will not warp or bow.

The care of timber has improved too. There is great versatility with a choice of stains or paint finishes in any colour. With changes in modern processes such as microporous paint systems, you can expect a high quality paint finish to last for 8‐10 years without maintenance. Wood integrates nature with your home and offers a certain warmth, depth and texture that you cannot achieve with other materials, working well with both contemporary and period properties.

Aluminium frames

aluminium bifold doors from kloeber - grand designs

Image: Aluminium bi-folds, Kloeber 

If you prefer a slim, sleek aesthetic and contemporary styling then aluminium frames could be your ideal choice. They are light but very strong and allow for large panes of glass so can suit bigger apertures. Slim sightlines have become increasingly popular for sliding doors offering a frameless appearance with vast expanses of glazing for unadulterated views to the garden and beyond.

Aluminium frames are often specified on modern homes; however, they can be used successfully on period properties to create an effective contrast. A powder‐coated finish offers an appealing, durable, low maintenance surface and look for thermally broken aluminium to ensure a better thermal performance. Aluminium units are at the higher end of the market and will be more expensive than plastic and softwood designs.

Composite frames 

alud clad fixed windows and doors in modern home - grand designs

Image: Alu clad windows and fixed glazing, Kloeber 

If you can’t decide between timber and aluminium or you want to combine the properties and benefits of both, then alu‐clad or composite frames offer the perfect solution. An engineered timber interior and a thermally broken aluminium exterior creates a strong, secure, thermally efficient frame.

These frames can represent a higher level of investment but they allow for a modern looking aluminium exterior with the option of a softer, characterful timber interior adding warmth to living rooms and bedrooms. Alu‐clad works with contemporary as well as more traditional style homes, however, they may not suit all period properties so make sure you speak to a reputable supplier to discuss the options.

An experienced, knowledgeable supplier will be able to discuss your project in‐depth and recommend frame material options that would suit. They can offer guidance to help you make the right decision for your project. Why not consider a company that can offer survey, supply and installation services to streamline the process and to ensure peace of mind?


Are you in the process of choosing glazing for a self build or renovation? Share your thoughts with us by tweeting us @granddesigns or post a comment on our Facebook page.



What to consider when choosing glazing for your self-build

How to brief a builder on a home renovation project

5 top tips for hiring and working with an architect

Kevins Column

Grand Designs Live: Ask an Expert Weekend 22-23 May 2021

Discover free home project advice and product recommendations from the comfort of your own home. Register now to express your interest.
Self Build Homes

Bespoke architect designed homes that embrace their locations

With a bespoke architect-designed home you can create a house that suits your practical and aesthetic needs while ensuring it blends into its surroundings
Self Build Homes

6 self builders who carried out the building work themselves

To beat budget restraints, these have-a-go heroes rolled up their sleeves and tackled the construction of their homes themselves.
Self Build Homes

Tour this Canadian lakeside retreat, designed to endure extreme climates

Using sintered stone, this home has been created to survive Canada's extreme weather conditions.
Self Build Homes

Award-winning architects for design-led homes

The finest architects don’t just focus on your home’s exterior – they offer a complete service that marries the house’s form with a stunning interior....
Self Build Homes

How ground source heat pump systems can save you money on your energy bills

Opt for a ground source heat pump system with smart controls that can help cut energy bills and cut down on carbon use.
Self Build Homes

Off grid homes: 5 UK self builds for eco-friendly living

Self sustainability was the goal of these off grid homes in the UK. Read how these self builders achieved it.