What is Sarking on a Slate Roof and Why is it Installed?

Sarking, or insulation foil, is a flexible plastic sheeting with foil laminate applied to one side. It is applied on top of the rafters and under the battens the slate tiles are mounted to.

Sarking has several benefits which include:

  • Provides good weather protection during the installation of slate tiles
  • Prevents dust from entering your ceiling cavity
  • Creates additional insulating to your ceiling batts
  • Offers temporary weather proofing if your roof slates get damaged

A Byproduct of Space Program Technology

Outer space is much more brutal than Melbourne weather. Interestingly, though the benefits of foil insulation were well known decades ago as the result of the space program, only more recently have those benefits been applied to home insulation technology.

Foil insulation provides a “radiant barrier” that works equally well to retain heat in your home during cold weather and inhibit solar radiation (heat) from entering during hot weather. Heat transfer is accomplished through the infrared spectrum and foil thwarts that transfer so effectively that it’s used in outer space.

The conventional batt insulation in your home only slows down this transfer and becomes a radiant sponge in the process—soaking up heat only to leach it toward the cold. A little known law of temperature exchange is that heat seeks out cold. Summer heat seeks out the cooler air in your home. In the winter, cold is not actually coming in, heat is going out.

Understanding this nature of temperature exchange will help you realize why your home heats up noticeably at the end of a summer day and into the evening. Once your batt insulation is overwhelmed with stored heat from the day, it begins radiating it inward toward your cooler living space.

Foil inhibits this process by bouncing the heat back toward its source, therefore keeping you cooler in the summer and warmer in the winter, all while reducing energy bills. You may not think of a new slate roof as being a means of reducing energy bills, but because we use sarking on all slate roofing projects, you’re getting this additional benefit too.

How Long Does a New Slate Roof Last?

There are basically 2½ answers to this question:

  • As little as 10-12 years with signs of failure as early as 3 years
  • As much as 150 years or more—or somewhere in between

To arrive at the answer for you, it’s like pretty much anything else in life; the quality of materials and workmanship will determine the lifespan of your new slate roof. That will come as no surprise so let us help you better understand how to acquire a slate roof you’ll only need to do once in a lifetime.

One good reason so many Melbourne homes and buildings have slate roofing is the proven performance to withstand everything the Melbourne climate can throw at it: salt air, high velocity winds, torrential downpours, hail, snow and ice, intense solar heat and rays, our roofs take a beating. Yet there are period homes in excess of 150 years old with the original slate roofs. That’s proven performance!

To achieve that on your own roof, you’ll need roofing slate with proven performance and a slate installer with proven experience. You also want to be sure you’re getting a written warranty.

Since we’ve outlined these important factors, it’s only fitting we include our own credentials. We’ve been doing slate roofs since 1980 and the experience predates that back to the 1970’s apprenticing under a lifelong master slater. Most of our slating team members exceed 10 years experience. Our workmanship warranty is 50 years and we offer slate tiles with up to a 100 year warranty.

Qualified slate roofing companies are easy enough to identify because they can prove their experience and are not put off by your wise concerns. The dodgy slate roofers do not stand up well to scrutiny. Considering what’s at stake, that bit of due diligence on your part is well worth the effort. Do that and the 100+ year life expectancy on your new slate roof will be your reward.

What Maintenance Does a Slate Roof Require?

Many of the slate roofs around the Melbourne area, like many other places, are located in leafy places. A leading cause of slate roof failures that we see is from leaves and other debris clogging the gutter and drainage system. For this reason, an annual or biannual cleaning of the gutters is highly recommended.

Beyond that, a properly installed new slate roof of good quality, or a fully restored original slate roof, will be essentially maintenance free for many years. However, as the slate roof ages, we advise a professional inspection at least every 2-3 years. Many homeowners wisely choose an annual inspection to safeguard against unpleasant and expensive surprises from water damage.

This isn’t technically maintenance but a word of caution is also appropriate. If other services such as painting, TV or satellite antennas, solar heating, and so on are performed on your home or structure, a slate roof professional should also be consulted. Other tradesmen, or kind souls helping out, are not always aware of the damage they can inflict on a slate roof.

The operative word here is good quality slate properly installed. Once you have that, very little maintenance is required.

What Type of Roof Slate Should I Use On My Home?

The short answer is the best you can find and/or have a proven master slater help you choose. When it comes to slate tiles, the illusion of a low price often serves as a disguise for your most expensive option, especially given the fact that once you get burned, you’ll end up paying what you should have invested the first time.

The advice to speak with a professional isn’t just because of our bias as professionals, it just makes sense for many reasons. The know the characteristics and quality of slate on the market, they can evaluate the style of your home and offer the best choice of options, they can listen to your needs and preferences before offering your most suitable choices, you can see and feel the slate material you are considering, and the consultation to provide these services is usually free.

Once you have been presented with your slate choices, the slate roofer, or slate tile supplier, can provide pictures of homes completed with the slate tiles you are considering. Even better, you may be able to see the home or homes which is far better than a picture. We would recommend viewing the oldest example so you can see for yourself how well the slate tiles have aged.

If you’ll permit us a self promotional boast, Abardeen has been slating roofs since 1980 and we’ll gladly show off our earliest work because we’re quite proud of it.

This ought to be your instinct but we’ll mention the importance of a written guarantee anyway. Ours is 50 years on the workmanship and you can get up to a 100 year warranty on our favorite and best slate tiles. By contrast, we’ve seen slate roofs fail in as little as 3-4 years so that warranty is really, really important!

Follow these guidelines and you’ll discover your choices in color, texture, quality, longevity, and everything else you need to make your home and slate roof aesthetically beautiful and stay that way.

What Roof Frame Structure is Required for Slate Roofs?

We get this question quite frequently, mostly from architects and builders, so we wanted to answer it as best we can. There are of course variables and we’re answering it from the perspective of our market here in Melbourne, AU but the principles apply elsewhere. The answer is also technical, but that’s okay since usually only technical people ask it.

The simple answer is to design and build according to the structural requirements used for terracotta roofing tiles. The weight of the lightest “Marseille” pattern terracotta tiles currently available in the Melbourne area is almost 10 kg/sqm heavier than the commonly used Del Carmen 500×250 slate tiles.

Here are some approximate weight comparisons for roofing tiles:

  • Natural slate – Del Carmen 500×250: 30.5 kg/sqm
  • Terracotta tiles – Marseille pattern: 40kg kg/sqm
  • Terracotta tiles – Swiss pattern: 43.5 kg/sqm
  • Concrete tiles – – Flat slate pattern: 52 kg/sqm

The terracotta and concrete tiles listed are also the lighter weight options available. Other tiles on the market are considerably heavier. Also be aware that slate tiles vary in thickness and therefore also in weight. Plus, as the dimensions of slate tiles decrease, the weight per sqm increases conversely. Larger tiles reduce the per sqm weight.

The 500×250 though is the most commonly used in the Melbourne area. Other options include 400×250, 450×250, and 500×300.

Another consideration during roof framing is the heights at which fascias, tilt battens, verge, sole and lear gutter boards, etc., are set and finished at. This is nearly impossible to give a generalized answer on since there are many factors at play and each job has its own set of unique circumstances.

If you’re in our service area, a simple phone call to Abardeen Slate Roofing at (040) 302-2137 is the best answer we can give. We work directly with architects, builders, and the carpenters doing the framing to assure the framing method matches the slate roofing tiles that will be used. If you’re not in our service area, a good slate roofer will offer the same service because it benefits everyone.

Why Do So Many “New” Slate Roofs Fail?

The answers to that question probably aren’t going to offer very many surprises, but the one factor that does surprise people is how quickly a new slate roof can fail. It can happen in as little as 3 years! Most owners of a bad slate roof learn that lesson the hard way but if you’re one of the few people who ask this question beforehand, congratulations.

This is going be less about why a slate roof can fail so you can avoid having it happen, or worse, having it happen again if you’ve already been burned. Knowing why they fail does equip you to avoid the heartbreak and expense of a failure.

Not all slate is created equal

In other words…quality. Slate is a natural product. Many people falsely assume that because slate is mined from the earth, it is essentially all good. That is very incorrect. The facts are that slate varies widely in its resistance to moisture and water absorption, delaminating, its stability and longevity, and its overall suitability for being used on your roof.

Another factor that is not helping your situation is that testing slate quality is voluntary so a great deal of slate being sold on the market isn’t tested, or it is only tested for a standard used to mislead uninformed buyers. The downside for natural products is they don’t have the same accountability that applies to the manufacturers of manmade roofing products.

There are stringent testing standards like the French NF30 which is generally regarded by experts as the most rigorous testing standard in the world. Having slate tiles that pass tough testing standards may appear to make them cost more, but the reality is, if you don’t have the right slate quality installed, you’ll just spend money on better quality later, and that’s the real expensive option.

Poor quality workmanship

Again, no surprises as we state the obvious, but unqualified slate roofers are at least as bad as poor quality slate material. We dedicated much of our previous post (and other posts) into some basic rules for qualifying a good slate roofer, but because so many new slate roofs in the Melbourne area have suffered the consequences of poor quality workmanship, we can’t overemphasize how important this is.

Melbourne is subject to torrential downpours. That’s what makes slate such a great choice when quality tiles are properly installed. But improperly installed, all the benefits get cancelled out. Melbourne is also subject to some high velocity winds. Properly installed, your slate roof is like armor plating. But poorly installed your slate tiles can become dangerous projectiles posing a serious threat to persons and property.

Climbing on the roof

Slate roofing will withstand everything nature can throw at it better than any other roofing material. People on the slate roof does not fall under the nature category. You should consult with a slate roof professional before anyone climbs on the roof. A satellite dish, skylights, or a better view are not worth ruining your slate roof for.

Warranty for a New Slate Roof

A particularly loaded question slate roofers get asked is, how long will the slate roof last, or, what is the warranty period?

One reason this is such a loaded question is the diversity among the slate roofers you would pose the question to. We of course can only answer that question for ourselves and not the other roofers. The short answer is we have a 50 year installation warranty. If you choose our highest grade Del Carmen slate tiles, the warranty is 100 years!

A slate roof should last you in excess of 150 years.

That’s the good news. It won’t surprise you that our statement about good news means we also have bad news. We’ve seen slate roofs fail in as little as 3-4 years. Not the ones we do, but unfortunately, anyone hiring a slate roofer can get burned if they take a warranty at face value.

We would never make an erroneous claim that a fair market price guarantees anything in choosing a slate roofer, but it is most definitely true that a low price is a major red flag and you are pretty much guaranteed to be buying a nightmare. Low price accompanies getting burned a whole lot more than often than not.

The roofing trade is high up the scale of industries prone to be populated by shady participants. It’s amazing how often and seemingly easily they find someone to rip off. The reason we call that amazing is that it’s fairly easy, and intuitive, to identify a qualified roofer.

Here are a few basic rules:

  • Length of time in business – One of the leading traits of a scammer is here today, gone tomorrow. Hiring someone without a demonstrated business history is a huge risk. For the record, Abardeen has been doing slate roofs since 1980.
  • Experience – Slate roofing takes years to master so experience is a must. Any company that hires slate roofers as a “summer job” should be avoided. This is a good place to mention most of our slate roofers exceed 10 years in their experience.
  • Specialize in slate roofing – Slate roofing is not something to “dabble” in and good slate roofers don’t dabble, they love what they do. If you don’t love it, you won’t want to do it. If slate roofing is a menu item on the list of services, you’ll do well to look elsewhere.
  • Reputation – A good reputation can’t be easily faked. The late former US President, Ronald Reagan, made the famous statement, “Trust but verify.” That’s good advice.
  • How the scaffolding is supplied – A serious slate roofer should own their own scaffolding. If the roofer needs to rent scaffolding, that signals a lack of business strength and opens you up to a couple of primary problems and risks. First, if they don’t complete the roofing on schedule, the rental prices escalate fast. You’ll pick up the tab. Second, renting the scaffolding naturally leads to taking shortcuts to reduce rental costs instead of taking the time to complete your slate roofing properly.

If you take this short list of intuitive steps to evaluate a slate roofer prior to hiring them, you can be confident any warranty they provide will be more than a worthless sheet of paper.

How to Tell if You Need a New Slate Roof

Waiting until the obvious signs appear like ceiling stains, buckled walls, and chunks of wall and ceiling material falling would be the worst advice for detecting the need for a new roof. Visible damage means the things you don’t see have been a long time in the making and the “maturity” of that damage will cause deep wounds in your economic situation when you’re faced with fixing it.

Like pretty much anything else in life, early detection of the need for new slate is your best defense and least expensive option. If you suspect that your old slate may be getting tired, you can have a professional inspect it for you, but inspecting it yourself is an easy and viable option if you are able to access the underside inside the ceiling cavity.

Yes, it’s the underside of your slate tiles that tells the real story. Failing slate tiles will exhibit easily identifiable characteristics, including:

  • Delaminating, flaking, and peeling
  • White, powdery surface formation
  • Softness

Those visible signs are easy to see. You may even observe color variations that signal moisture penetration. The surest sign of leakage in the near future is softness. Good slate tiles will be firm and hard.

To check for softness, a standard screwdriver is an easy test. Apply a firm pressure as you drag a screwdriver across the underside of your slate roofing. If you can easily score the slate tile, you can be sure it’s time for new slate on your roof. It’s a good idea to perform this test in multiple locations.

There, if you thought that might be difficult, you can be pleasantly surprised. If your roof passes these simple tests, you have peace of mind on the structural integrity of your slate roof. If it doesn’t pass, some of the other information on this site and blog will help you find a reputable and experienced slate roofer.

New Slate Roofing On An “Old” Roof

In case you’re wondering if Abardeen will re-roof an “old” structure with a new slate roof, the answer is emphatically, yes. But next, you may be wondering what the process looks like.

  • Will it be messy?
  • How long will it take?
  • How much inconvenience will it cause?
  • What effects might it cause to your property?

Maybe you’ve seen a slate roofing project that was an eyesore and pretty much met every stereotypical nightmare you could have envisioned: big stacks of material for weeks on end, debris strewn all over the place, you name it, that’s what it looked like. There are slate roofing contractors that operate that way, but here is what you should actually expect.

First, scaffolding is set up for the safety of both the workers and anyone on the ground. We are especially careful to avoid damaging property, landscaping, gardens, etc. Only a few areas are set up at one time so walkways, driveways, and other access points are not blocked any longer than required.

One the first day of your project, and each day thereafter, materials for that day are brought to your site so you will not be supplying a warehouse location. For each day of your project, the section of your old roof for that day will be stripped and stacked on the scaffolding. Very rarely do we need to place materials on the ground but an out of the way location is chosen when needed, and cleanup is always prompt.

New slate tiles and any required flashing will be installed on the section stripped. At the end of the day, you are waterproof, clean and tidy, and debris is hauled off in our trucks. No, dumpsters are not left on your property during the project.

Rinse and repeat: This process continues each day until your new slate roof is complete.

Inconvenience? Minimal to non existent.

For an average sized Melbourne area home, this process takes about two weeks. You will always know in advance the actual time required for your project. Once we are done, you won’t know a roofer was ever on your property except for the beautiful new slate roof. The Boy Scouts of America have the motto, “Leave no trace.” That sums up our philosophy as well.

See an example of a slate re-roofing project

The Slate Roofing On Your New Building Project

If you’re the builder or the owner of a new building (or new home building) project, you realize how interdependent all of the contractors are on each other to keep everything on schedule. That would especially apply to having a new slate roof put on. Many of the contractors can’t complete their part of the project until that new roof is finished.

Here’s a brief overview of items you should consider when hiring a slate roofing contractor:

  • Experience – Slate roofing requires years of experience and practice under the apprenticeship of a master slater to truly acquire the skill needed.
  • Reputation – As already pointed out, contractors depend on each other to complete a project on schedule. You want to be sure your slate roofer has a reputation respected by other contractors.
  • Safety – Not only is the safety of workers on the roof paramount, extra precautions need to be taken to insure the safety of everyone working below them. If the roofing quote is temptingly low, safety shortcuts are almost certainly being taken because you may not think to question this in advance.
  • Framing – Be sure the carpenter or framer has been provided with the proper specifications for the slate roofing being installed. Having an experienced slate roofing contractor involved in the early stages of your building project is highly advisable.

A new construction project should be exciting for you. Having something as beautiful and enduring as a slate roof should add to the excitement. Look around some of the Melbourne neighborhoods at other “new” projects and you’ll see not everyone gets exciting results. That’s sad but it doesn’t have to be that way. These few simple guidelines will help you remain excited even decades from now.