How to Slate a Roof

Slate roofing has become hugely popular as a roofing material for homes and buildings around the country. Not only do roof slates create an effortlessly beautiful look for your property, but they also provide great practical and environmental benefits, as well as boosting the value of your home.

Unfortunately, due to the premium nature of a slate roof, you’ll be paying more for both materials and labour. This has led to many homeowners considering installing their new slate roof themselves. But how do you lay a slate roof? In this article, we’re going to explore everything you need to know about fitting a new slate roof.

Types of Slate Roof Tiles

There are many different types of slate roofing to choose from, but which one is right for you?

Natural Slate

Welsh

If you’d like to add a touch of timeless beauty to your property, look no further than Welsh Slate. Welsh slate roof tiles are some of the most popular, thanks to their combination of gorgeous aesthetics and excellent durability. Due to the environment in which it is extracted, Welsh Slate is naturally resistant to acids, alkalis, and UV light exposure. It offers an impressive life expectancy of 70 years or more, and even lasted for over 400 years atop St Asaph Cathedral.

Canadian

Canadian Slate is one of the highest-quality roofing materials available to homeowners. The ultra-tough structure and stunningly deep colouring of these slates is thanks to the harsh environment in Quebec, where most of them are extracted. The charming appearance of Canadian roofing slate lends itself well to a multitude of property types, whether you’re re-roofing your home or a larger period structure. These slates also produce very little CO2 during their manufacturing process and can be recycled at the end of their 75+ year life.

Spanish

Sourced from a range of idyllic locations across the country, Spanish Slate is best known for its stunning depth of colour and timeless character. Spanish roof slates add plenty of kerb appeal to virtually any property, and age beautifully across their lifespan. Plus, due to their exceptional strength, these tiles hold up brilliantly against the harshest of weather or environmental conditions. Crafted entirely from natural stone, they’re an excellent green option to reduce the impact of your project.

Fibre Cement Slate

Fibre cement slates are ideal for homeowners looking for the beauty of natural slate at a fraction of the cost. Available in a range of stunning finishes, fibre cement tiles add plenty of character to any property they adorn. They also boast impressive durability, along with an expected lifespan of 50-60 years. Due to their lighter weight, fibre cement can be used on many different structures, including residential properties and commercial premises. Plus, these tiles will require minimal maintenance across their lifetime.

Synthetic Slate

Both natural and fibre cement slates can be too heavy for many structures, which has led to the creation and rise of lightweight artificial slates. Crafted from a mix of recycled limestone and plastic, these tiles are a practical alternative that can be used on even lightweight timber structures. Designed to mimic the aesthetics of natural slate, you’ll hardly notice the difference. Plus, these tiles are considerably easier to work with and install.

How to Slate a Roof with Natural Slate

1. Measuring Your Roof Pitch

The very first step in any roofing project is working out the pitch of your roof. This is a vital part of working out how many tiles you’ll need, and the amount of overlap when laying each slate. Typically, slate can only be used on roofs with pitches of 20° or more, but this can depend on the exact slate tile you choose.

Read our handy blog to learn how to work out your roof’s pitch, and then consult the manufacturer’s guide for the required overlap.

2. Fitting the Roof Membrane

Choosing a high-quality roof membrane will keep your roof space protected against water ingress, and ensure long, reliable service from your new slate roof.

 Before rolling out the membrane, you must ensure that your rafters/trusses are completely clear of splinters, old nails and any kind of debris that could damage it. Once completely clear, start at one bottom corner of your roof and roll the roofing membrane out along the trusses. Moving around the roof space, use this method to continue rolling out the membrane to reach the top of the roof.

After rolling and completely covering the roof with the membrane, secure one edge using clout nails. Then, pull the roof membrane so it is tight on the opposite end and fix with clout nails. Secure a few more clout nails at the point that the membrane joins with the trusses.

TIP! – Make sure your roof membrane hangs over into the gutter to allow effective water drainage.

3. Setting Out Battens for a Slate Roof

First Batten

Now the roof membrane is securely fitted, it is time to figure out the placement of the battens. For this step you will require two full sized slates and one under eaves slate. Place two battens onto the roof but don’t fix down. Take one full sized slate and place onto the batten, allowing for overhang (overhang is recommended to be around 50mm). Make sure the pre-drilled slate holes fall into line with the centre of the batten. Fix using temporary fixings.

Second Batten

Placing a second batten beneath the slate tile, carefully move it in an upwards direction towards the batten you placed first. Position the eaves slate onto the second batten. Make sure the eaves slate can reach the bottom edge of the roof.

Using galvanised nails, securely fix both battens ensuring they are parallel before doing so. To check this, measure from various points along the roofline. If the difference in this measurement is the same, the battens are parallel.

Third Batten

Move a third batten down so it is positioned below the top of the slates. At this stage, the top of the full-sized slate should be central to the batten.

Take another full-sized slate and position it on top of the third batten. Once again, ensure the pre-drilled slate holes are aligned with the batten centre.

Batten Gauge

To calculate the batten gauge, measure the distance from the top of one batten to the top of another. Once you have the batten gauge, you can position the battens on the remaining area of the roof based on this measurement.

4. How to Lay a Slate Roof

After positioning and securing all of the battens, you can now begin laying the slate tiles. This step may seem complicated, however when you understand the technique, you will soon have your whole roof fitted in next to no time.

Start by making a line with chalk from the eaves to the ridge to the width of each slate. Allow 5mm for the joint between each slate onto the battens.

Start at the eaves, fixing the under eaves slate course first. To begin the course, use a one-and-a-half slate to form a staggered pattern. Creating a staggered pattern will help to increase roof stability. Remember the 5mm gap between each to allow for expansion.

Once finished, lay a full length slate with the bottom tile positioned inline with the under eaves course. Use two copper nails to secure.

Continuing the method, work upwards until you reach the top opposite corner. Laying the slates this way will reduce the amount of foot traffic on the slates whilst fitting.

When you reach the very top of the roof, you will need to install top slates. Make sure the batten positioned at the top of the roof is 5mm thicker than the others.

TIP! – You should ensure that each slate is fitted with at least two nails, however, don’t overuse.

How to Fit Ridge Tiles on a Slate Roof

After slating your roof, one of the final steps is fitting ridge tiles onto the structure. Ridge tiles are designed to finish the roof structure, protecting it from the elements. They are usually installed in the same or a similar colour to the slates and will commonly be seen in two shapes – round or angular. Angular ridge tiles are more commonly used for slate roofs.

Mortar Bed

When fitting ridge tiles onto a slate roof, you need to ensure the edge of the tile seals the top of the slates by a minimum of 75mm. This can be done using a mortar bed of 3:1 sharp sand to cement along the edges of the ridge tiles and slates. Use the solid bed of mortar at the ends of the ridge tiles to fill in the gap where they meet, then use a piece of flat slate to bridge the gap between the tops of the slates on both sides.

Push the ridge tiles down firmly into the mortar beds to set. Remove excess mortar that was pushed out and smooth the joint.

Mechanical Fixing

A lot of manufacturers now utilise mechanical fixing systems for ridge tiles instead of the mortar technique. The mechanical fixing system will usually include side sealing pieces, end sealing pieces, a special ridge board and fixing nails or screws.

The side sealing pieces are laid along the sides of the ridge, creating a seal between the ridge tiles and slates whilst the end sealing pieces straddle the end of the ridge tile. A ridge board is fitted above the apex of the trusses to take the ridge tile fixings.

The system will differ from brand to brand, so it is always key to reference the manufacturer’s guide for installation advice and information.

How to Slate a Roof with Fibre Cement

1. Tilting Fillet

To ensure the underlay doesn’t sag between the rafter feet, use a tilting fillet to support behind the fascia. To finish, the underlay should hang into the gutter. This is to ensure that moisture on the underlay drains effectively into the gutter with no moisture build-up. The eaves should not be sprocketed because this may hinder the installation of the disc rivet at the tail of the eave’s course.

What is a Tilting fillet? A tilting fillet is a wedge-shaped strip of wood that is fitted beneath the slates to tilt the bottom course.

2. First Course

In total, you will require three slate courses at the eaves. The first under eaves course should be cut, drilled and head nailed to the length of the batten gauge. It is recommended that eaves overhang by 50-55mm for 100mm gutters. To begin, centre the first under eaves slate at the centre point of the eaves. Take time to locate this before beginning installation.

After fixing the under eaves slate, position a full length slate over the top, cutting the slates on both verges to the same width. Continuing to utilise this method, move across towards both verges, fitting the rest of the under eaves slates.

3. Second Course

Cut the second under eaves course from the same slate as the first. The length for this is the batten gauge + the slate headlap. Fit the second under eaves course so it covers half the width of the first. Allow the shank of the tail rivet for the first course to pass between the adjoining second course of slates, oversailing the fascia 50-55mm.

4. Align & Overhang

Secure the first full slate course to the second batten with the tail trivet passing between the two second under eaves slates. It should extend through the hole in the tail of the full slate. You must be sure to check that the first full slate course overhangs the gutter by 50-55mm

At this stage, the tails of all three slate courses should be in line, overhanging the gutter. Ensure this is the case before moving to the next step.

5. Final Steps

You should ensure that the verge slate on alternate courses is a slate and a half width cut from a double slate. This is in order to create the correct bond. You will need to pre-drill holes into the verge slates for three nail and two rivet fixings, as well as one extra hole. The extra hole will allow the tail rivet for the course above to pass through the slate and a half.

The following single verge slate will also need an extra hole for the tail rivet of the next slate and a half. Remember, tail trivets should always pass between two neighbouring slates in the tail of the slate they are holding. The overhanging shank of the rivet will be bent down the slope. 

How to Replace a Roof Slate

After installing your roof slate, you may find that from time to time, you need to replace a broken or missing roof slate. So, what is the process for this?

In our handy ‘How to Replace Roof Tiles’ article, we talk you through the simple process of replacing a slate roof tile, as well as a look into replacement costs and answers to any further questions you may have.

Cost of Slating a Roof

Professional roof slating jobs have the potential to get pretty expensive including labour costs. So, how much does it cost to get the job done yourself?

In the following table, we have compiled a list of various types of slates and the average prices of each to give you a clearer idea of slate material costs.

Type of Slate

Average Price per item (inc VAT)

Product

Welsh Slate

£2.50

Redland Cambrian Slate - Interlocking Slate Tile

Canadian Slate

£4.61

Cembrit Glendyne - 4-5mm Natural Slate Roof Tile

Spanish Slate

£1.58

Samaca Q33 - Natural Spanish Slate

Fibre Cement Slate

£3.35

Cembrit Moorland Fibre Cement Slate

Lightweight Slate Tiles

£1.98

Tapco Synthetic Slate Tile

How to Climb and Walk on a Slate Roof

Although slate tiles are generally very durable and weatherproof, it is always important to climb and walk across them with great care. It is especially important to follow this guidance if you are working on an older slate roof as the slates may have been subject to deterioration, hence making them weaker and more fragile.

Generally, it is recommended that you minimise the amount of foot traffic on your slate roof and try to avoid walking across it altogether. However, there are a few ways you can enhance the safety of yourself and of your slates to reduce the risk of damaging your slate roof when working on it.  

Ladders – The type of ladder generally recommended for working on slate roofs is a hook ladder. Hook ladders are designed to hook over the ridge of the roof, allowing the roofer to walk on the roof structure without putting weight on the roof itself.

Footwear – When walking across slates you should always wear shoes with a soft sole. Very heavy work boots are far more likely to cause damage to the slates, so going as light and soft as possible whilst still protecting your feet is advised.

Weight Transfer – Always make sure you are evenly distributing your weight when walking across any tiled roof. Transfer your body weight gradually from one foot to another as you walk and walk using the ball of your foot. Never jump or leap between slates.

To Conclude

Slate roofs are a popular for a reason. From their elegant style and aesthetics to their fantastic durability and impressive lifespan, slates offer an abundance of benefits that make them suitable for a wide range of properties.

If you are thinking of installing your own slate roof, then why not have a browse through our affordable, high-quality range of roof slates to get your project started? Whether you are in search of natural slates, fibre cement slates or plastic slate effect roof tiles, we stock a wide range of varieties from leading brands you can trust.

Alternatively if you have any further questions or queries, don’t hesitate to get in touch with our award-winning customer service team who will be more than happy to help. Simply give them a call on 01295 565565, email sales@roofingmegastore.co.uk, or leave a message in the handy live chat.