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The content contained in this Good Roofing Guide article is for information purposed only. While every effort is made to ensure this article is accurate at the time of posting, JJ Roofing Supplies would recommend that you always seek to use a professional roofer for completing all roofing related jobs.

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How To Guides

How to Lay or Replace a Slate on a Slate Roof

Slate is a very popular material for covering a roof, requiring a specific process for laying and repairing a slate roof. If maintained properly, it can look very aesthetically pleasing as well as protect your roof against the elements.

If you are looking to lay a slate roof, or replace one or more broken slates, this article will detail all the steps you need to follow. Learning how to slate a roof is an invaluable skill and will save you time and money.

Before we carry on have a look at our slate range. JJ Roofing Supplies stocks and sells a wide varierty of different slates. 

Safety

The first rule of learning how to slate a roof is knowing the correct safety procedures. Treat all roof coverings as fragile and take the necessary precautions in protecting the fixed material when either slating a new roof or replacing a broken slate.

When working on a slate roof, you should ensure there is adequate protection in place, such as scaffolding. Keep a ladder fixed firmly to the side of the roof, and it is always a good idea to have someone at the bottom holding it in place. Always wear appropriate clothing and footwear, such as gloves, a hard hat, and rubber-soled shoes. Learning how to slate a roof is much about protecting yourself as it is completing the job correctly.

Underlay

The next thing to consider when learning how to slate a roof is the underlay. With all the rafters fixed in place, you first need to roll out and secure your underlay. Starting at one side of the roof, ensuring the underlay is laying flush against the verge, nail the start of the roll in place against the furthest rafter. Then, roll it out along the length of the roof. Nail the other end in place, keeping a little slack in between the rafters.

You can nail it in place along the middle if desired, but this is not strictly necessary, as the battens you fix on later will hold it in place. Repeat this process until this section of the slate roof is covered.

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Battens – getting started

With the underlay secured, you need to figure out where your first battens will go, using two fully-sized slates and one under eaves slate. Place one full slate at the lowest edge of the roof, bearing in mind how much overhang there should be into the guttering, normally not less than 50mm.

To set the first batten, this is calculated by, the lap plus the batten gauge plus 50mm, therefore allowing for the 50mm into the gutter work back and place your batten under the head of the under eaves slate and fix. Your next batten will take the first row of the eaves course, line up with tails together and place the next batten where the holes appear in the first full slate and fix into position.

Your slate roof manufacturer will likely specify how much slate lap you need to accommodate for - this is a crucial thing to remember when learning how to slate a roof. ‘Slate lap’ is the amount of overlap there is between the nail holes of one full-sized slate and the bottom edge of the slate on top of it. To batten out the rest of the slate roof use the gauge supplied or use the following calculation; length of the slate minus the lap divided by two, this will give you your batten gauge centre to centre.

Setting out and laying your slates

The key to figuring out how to slate a roof is in learning how to set everything out correctly. Strike a chalk line from the eaves to the ridge to the width of every slate allowing 5mm for the joint between each slate, on to your battens.

Fix your under eaves course (e.g. slates with the reduced length), these should be laid first, beginning with a one-and-a-half slate to create a staggered pattern, (have slates less than 150mm should not be used). Keep a 5mm gap between each slate (to allow for natural expansion in the slate roof structure) so they are not completely rigid.

Lay your first full-length slate with its tail aligned with the under eaves course and nail with two copper nails 35x3.35mm gauge.

Slowly work your way upwards as you lay the slates, so you progress from (for example) the bottom-right to the top-left. This will limit the number of slates you have to stand on in the process, reducing the risk of any of them cracking, and making sure each slate has a minimum of two nails per slate. Do not over nail - so long as you remember this, you'll do fine when learning how to slate a roof.

The very top row will require top slates – which are, like eaves slates, reduced in length – in order to finish off the look. The top batten that takes the tops slate should be 5mm thicker than the main battens so that this slate doesn’t ‘cock up’.

Replacing a Slate on a Slate Roof

All slates are likely to be nailed into place, so in replacing one of these slates you will need to remove the nail. For this particular task, you will need a slate ripper, tins snips, and a hammer, as well as a slate trimmer if you need to alter the size of the slate you’re fitting – we’ll call it Slate Y for the purposes of this explanation.

Feed the hooked end of the slate ripper underneath Slate X (the slate you want to replace), and trap the nail in the hook. Hammer on the handle of the slate ripper to force the nail out of place, and then pull the ripper out. Repeat this process for the second nail.

Following this, you should be able to slide Slate X downwards and out of position, applying light pressure to the top with the palm of your hand, and keeping the ripper underneath to help leverage it out. This is a crucial step when learning how to slate a roof, so be sure to keep this in mind to ensure success.

Slate Y must be a perfect fit for the space available, so use the slate trimmers to cut it down if necessary.

If you have removed more than one slate, you should be able to re-nail most of them to the timber battens underneath; remember not to nail them down too tightly or loosely – a 1mm gap from the slate surface should suffice.

For the final slate, you will need to secure it in place with a small strip of lead, long enough to be nailed into place against the batten, and stick out from and wrap around the bottom of the slate that will go on top of it.

Nail it in place, and then rest the slate ripper over the existing slates so you can slide Slate Y into position. You should see some of the lead at the bottom of the slate. Make sure Slate Y is level with the rest of the slates around it, and that it has been pushed up to rest on the batten underneath it.

The final step in figuring out how to slate a roof is in folding the lead over the bottom of Slate Y. Fold the lead over the bottom of Slate Y so it makes a small hook, and this will keep the slate in place. Use the lead snips to cut off any excess lead.

Laying and maintaining a slate roof does not have to be too tricky. Ensuring you have the correct tools to hand and take the time to prepare for and carefully plan out the work, you can create a neat and practical roof, and replace any slates that get cracked.

Hopefully, by following the advice listed above, you should have no problems handling replacing any aspect of your slate roof. For more information on how to slate a roof, be sure to give our team a call and remember, we’re the number one choice for roofing-related products and accessories.


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