Your Guide to the Best Sealants for UPVC Windows Outside

There is a wide range of window frame and glazing sealants available on the market, but how do you know which is the best fit for your windows? 

The primary aim of sealant is to keep your property free from moisture. Most window frames are subject to a degree of movement due to the sun and cold weather causing some materials to expand and contract, so it is important that your chosen sealant offers flexibility. 

This guide explores some of the best sealant options for outside UPVC windows in addition to explaining which other materials these sealants work well with.

Things to Consider When Choosing Window Frame Sealants

There are a number of factors that you should consider when narrowing down your options for window frame sealants. 

One of the most important factors will be the material of your window frame as some sealants adhere better to certain materials compared to others. 

Additionally, it is also important to know that some sealants are better suited to exterior use and others for interior use. When sealing external frames, it is better to go for those designed for weather resistance. 

You should take the frame movement due to expansion and contraction into account, as using a window sealant suited to high-movement or expansion joints will benefit you in the long run.

Top 5 Sealant Options for UPVC Windows

Low modulus-based silicone sealants can be used both internally and externally in most cases, and this kind of sealant is recommended for most window frames. 

It offers optimal levels of flexibility to adhere to shifting weather in addition to providing long-lasting results.

Everbuild 825 LM

A low modulus, neutral cure, odourless silicone window frame sealant, the Everbuild 825 LM sealant can be used both internally and externally on a variety of window types. 

This highly versatile sealant is available in a range of colours to perfectly colour-match your home. It also effectively bonds to a wide array of materials without the need for advance priming:

• UPVC
• Wood
• Powder-coated aluminium
• Glass

The Everbuild 825 LM sealant is suitable for use on both porous and non-porous surfaces and is ideal for weather sealing, sealing glass to glass, and sealing glass to the perimeter of a window. It is also compatible with soft metals like copper.

Soudal Silirub LMN

This is a low-modulus silicone-based sealant which is suitable for most frame types. It is a high-quality elastic product which is available in a variety of colours, ideal for blending in with the aesthetic of your home. 

This product also boasts UV resistance, ease of application, and longevity long after the sealant has been applied to the desired surface. 

It offers excellent adhesion to: 

• UPVC
• Treated and untreated wood
• Metals
• Glass
• And more

Soudal Silirub LMN is highly flexible, making this a good option for high-movement joints and joints subject to contraction and expansion from the sun.

Everbuild 950

Cost-effective and easy to use, the Everbuild 950 window sealant is a low modulus sealant which is compatible with a wide range of surfaces and can effectively point external and internal perimeters.

This product is suited to a wide range of materials, including:

• UPVC
• Wood
• Glass
• Aluminium

In addition to creating a seamless, secure, and aesthetically pleasing seal, the Everbuild 950 window sealant can be simply applied to the desired surface without the need for priming beforehand. 

This makes this option an excellent choice for larger-scale jobs and is an ideal tool for professionals who complete window sealing jobs on a regular basis. It is highly weather resistant, suitable for all kinds of general glazing, and even roof weather sealing. 

The Everbuild 950 also boasts excellent flexibility to provide longevity and value for money.

Arbosil LM

The Arbosol LM is a high-quality window sealant which comes highly recommended for the sealing of brickwork joints and UPVC window joints. 

It benefits from being a one-part neutral cure sealant, which allows it to form an elastic silicone rubber barrier when exposed to moisture, perfect for weatherproofing properties and increasing the longevity of newly installed windows. 

Arbosil LM is ideal for sealing: 

• Brickwork joints
• UPVC windows
• Translucent roof joints
• General glazing

CM Sealants SFS

This water-cured window sealant is suited for use in both building joints and glazing joints. It is manufactured from a single component and is highly versatile, excellent for a wide range of applications including sealing high-movement and expansion joints. 

The CM Sealants SFS is a low-modulus form of sealant which creates a flexible elastic seal when cured at room temperature. No primer or further preparation is required before application as it can bond securely to a wide range of different surfaces. Including: 

• Aluminium
• UPVC
• Wood

Once the sealant has cured on your desired surface, it offers a movement capacity of up to 50% over a range of temperatures, perfect for weather sealing and the longevity required from window sealants.