Plastic Window Trim – Everything You Need To Know

Window trim

Plastic window trim is generally used to fill the gap between a UPVc window and wall. It might not sound like the most exciting topic, but it’s an important detail when planning new windows for your home. Here’s the complete guide…

Used extensively within the double glazing industry, this flexible material neatly covers sharp edges and corners.

This linear profile is the icing on the cake in terms of window fitting as it matches or contrasts the colour of the window frame, giving an all round aesthetic finish.

Plastic window trim is usually added both internally and externally to a newly fitted window and can be cut to the desired length.

Easily attached with adhesive or silicone, plastic trim compliments and completes the fitting of UPVc windows and doors.

Why have plastic window trim?

Imagine a UPVc window fitted without a surrounding trim.  It would be quite ‘revealing’, literally.

The door jamb or window reveals are the architectural linings of any opening and not a pretty sight if left uncovered.

When a window or door is fitted into its aperture, leaving it without a trim would look pretty rustic; in professional terms, unfinished.

Without the addition of trim, the pointed corners of windows and doors would look awkward and present sharp edges.

Having plastic trim around your new UPVc windows or doors also provides a decorative finish, as this product comes in a variety of styles.

Fitting plastic window trim

Plastic window trim can be purchased in the larger, well-known DIY stores and is relatively easy to fit yourself, should you need to.

The recommended adhesive for fitting plastic trim to window and door surrounds is silicone.  This sealant is flexible and weathertight and can even come in different colours.

That said, window trim can also be fitted with tape or adhesive such as superglue.

If you are having new windows or doors installed by a double glazing company, then they will probably be fitting the trim as part of your overall cost. 

Check with your installers if you have particular requests on types of trim.  Even the best double glazing companies will use a basic but effective design.

Your trusted window fitter is likely to use a supplier for plastic trims who will guarantee the product for around 10 years against discolouration, warping and cracking so you can feel secure in the knowledge that both windows and accessories are protected.

Popular styles of plastic trim

Whilst there are some more unusual and less known styles of trim on the market, these are the most commonly used.

  •  Flat
  •  Angle
  •  Quadrant
  •  Concave
  •  Bead

Colours and sizes

Most popular styles of plastic window trim will be available in the same range of colours as for UPVc window frames so you can be sure to match and blend the surround seamlessly.

For windows and doors in wood finish, you can also choose matching brown trim or simply let your product stand out by framing it in white.

Depending upon your window style, window sill size and of course, personal choice, window trim is widely available in 20mm to 30 mm widths and usually sold in 5M lengths ready for cutting into required sections.

As a general rule of thumb, narrower trim looks good on contemporary style homes whilst the wider version suits a more traditional setting.

Window TriM FAQ’s

So, just to clarify some of the uncertainty about this functional product.

Why are there different names?

Plastic window trim can sometimes be referred to as casing. Window moulding can also be used to describe this decorative profile but most double glazing installers in the UK generally use the term trim.

Will the trim last as long as my windows?


Because this product its manufactured to the same high standards as your window frame, plastic window trim, with its durability and functionality should serve you as long as the windows.

Can plastic trim be replaced if necessary?

Accidents can always happen and if your UPVc trims are subject to damage such as knocks, scratches and marks, they can be easily replaced without impacting your window frame. 

Return to your purchase store or ask you window installer to reapply fresh trim to ensure a perfect match.

How much is plastic window trim?

Whilst plastic trim can vary in price, you will probably be able to purchase 5 metre lengths for around £15 currently.

Clearly, the price of plastic trim will be a little higher if you are planning on using an unusual or particularly decorative style. 

If you require coloured trim this may also cost you a little more.

So, just how important is plastic window trim?

In much the same way as placing a picture in a frame, plastic window trim is the perfect way to finish off your windows and doors.

Functional by giving a smooth and stylish edge, but also allowing homeowners to alter the aesthetics of their window frames by adding decoration and colour. 

Playing around with the possibilities of this much over-looked and yet economical product, will surprise you.

Try switching your plastic window trim for a new colour or shape to liven up old frames or spend time considering which trim is the best choice for your new double glazing products.

Either way, plastic window trim is here to stay and in great shape.

Matt James
Matt James

Hi, Matt here! I started out almost 20 years ago as a teenager working in the family business fitting doors, windows and conservatories. I now run this website to share the best tips and advice for anyone looking to get a good deal on double glazing.

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