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Can You Waterproof a Slate Roof in the UK?

Slate Roofing GL5 Roofers Gloucestershire Stroud

Slate roofs are a common sight across the UK, adorning everything from cottages to castles. Their natural beauty and durability make them a popular roofing choice. However, over time slate is susceptible to water damage if not properly maintained. The rainy climate in parts of the UK means slate roof waterproofing is an important consideration for homeowners.

In this comprehensive guide, we will cover:

  • The characteristics of slate roofs and why they may need waterproofing
  • Different methods for waterproofing a slate roof
  • Whether to hire a professional roofer or DIY
  • FAQs on slate roof waterproofing

Understanding Slate Roofs

Slate has been used as a roofing material for centuries thanks to its many beneficial properties:

  • Longevity – Slate roofs can last over 100 years if properly installed and maintained. The slate itself will not degrade or corrode over time.
  • Durability – Slate is very hardwearing and impact resistant. It stands up well to weather conditions like rain, snow, and wind.
  • Aesthetic appeal – Slate has a natural, textured appearance that many homeowners find visually appealing. Its layered structure comes in a range of earthy colors.

However, slate is still vulnerable in some ways:

  • Water absorption – Slate is porous and will absorb moisture over time, especially through capillary action. This retained moisture can cause damage.
  • Risk of leaks – Water absorbed into the slate or ingress through joints in the roof can lead to leaks, rot, and structural issues if left unaddressed.

Applying a protective waterproof coating to the slate is therefore recommended practice.

Methods of Waterproofing Slate Roofs

There are a variety of options when it comes to waterproofing a slate roof, from traditional sealants to modern liquid solutions.

Traditional Waterproofing Methods

Past generations relied on natural sealants like linseed oil to waterproof slate. While these can provide decent short-term protection, they typically need reapplying every 5-10 years.

Other traditional approaches include:

  • Limewash – A porous mixture of lime putty and tallow/linseed oil traditionally used to seal and color roofs.
  • Cement washes – Applying a cement coating to fill gaps between slates. Provides water resistance but can crack over time.

The effectiveness of these older methods tends to be limited – modern solutions usually outperform them.

Modern Waterproofing Solutions

In recent decades, advanced waterproofing products for slate roofs have been developed. These offer longer-lasting protection thanks to polymer technology.

Silicone-based coatings are one of the most popular modern solutions. They have benefits like:

  • Long lasting – typically 10+ years before needing reapplication
  • Excellent water resistance while allowing vapor to escape
  • Flexible – won’t crack or peel like cement washes
  • UV-resistant for continued exposure to sunlight
  • Various colors available to match slate roof aesthetics

When applied properly, silicone coatings provide superior wet weather protection compared to traditional approaches. They won’t change the breathability or original look of the slate either.

DIY vs Professional Waterproofing

Is it better to waterproof your slate roof yourself or bring in the professionals? There are good arguments on both sides.

Professional Slate Roof Services

Hiring an experienced slate roofing company has some clear advantages:

  • Expert inspection – Professionals will thoroughly assess your roof to diagnose any issues needing correction before waterproofing.
  • Proper repairs – Any damaged slate/flashing can be correctly replaced and the structure made watertight.
  • Superb application – Contractors have the right equipment, materials, and techniques to apply protective coatings evenly and effectively.
  • Can provide a warranty – Many companies guarantee their slate waterproofing service.

Typical methods used by roofers include:

  • Power washing the roof to clean it before application
  • Using rollers, brushes, or airless spray equipment to evenly coat the slate
  • Ensuring full coverage on ridges, joints, nail holes, and vulnerable areas

DIY Waterproofing

Ambitious homeowners can save on labor costs by waterproofing their own slate roof. However, there are some important considerations:

  • Safety – Use scaffolding and anchor points to avoid falls. Work with a helper.
  • Convenience – Transporting a ladder onto a steep, tall roof is challenging without a lifting platform.
  • Skill – Achieving a uniform finish across the whole roof takes practice. Missing spots can still allow water ingress.

Recommended products for DIYers include:

  • Masonry waterproofing paint with silicone or acrylic binders
  • Slate sealant like Stormdry Masonry Protection Cream

Be prepared to spend time preparing, applying carefully, and monitoring results. Also have contingency funds in case you need to call in a professional from the roofing Stroud to fix any substandard areas, reflecting contemporary practices.


Can all slate types be waterproofed?

Most common slate materials can be waterproofed including natural quarried slate, clay slate-style ceramic tiles, and synthetic reconstituted slate.

Always check manufacturer guidelines but generally silicone or acrylic-based coatings are compatible.

How often should it be applied?

Ideally every 10 years. Though some modern solutions claim to last for 15 years or more, periodic reapplication is advised. Harsher weather, roof pitch, and product choice affect durability.

Visually inspect annually and reapply sooner if any cracks, wear, damage or leaks are spotted.

Are there eco-friendly options?

Yes, there are slate waterproofing products that claim to use more sustainable formulas with low VOCs, non-toxic ingredients, and high bio-based content.

Linseed oil is a traditional eco-friendly choice but may need reapplying more often. Compatibility can depend on your roof material.

Can older roofs be waterproofed?

Yes, but the condition needs assessing first. Replacing broken slates, cementing joints, and fixing leaks ensures the coating adheres properly.

Acrylic coatings typically have better adhesion to aged rough slate compared to smooth silicone.

When do I know my slate roof needs waterproofing?

Warning signs to watch out for include dark moisture staining on sections of slate, white salt deposits (efflorescence), the growth of moss, lichen, or roof algae, leaks or damp spots inside the attic space, and visible cracks or missing pieces of slate; don’t wait until major damage occurs, address early signs of water ingress promptly.

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