Will Moss and Lichen Affect My Slate Roof?

Overall, moss and lichen will NOT adversely affect the integrity of your slate roof but there is one caveat to that answer.

Moss growth primarily occurs on the southern slope of your roof but can certainly grow on other slopes, just not usually to the same degree as the southern slope. We do not believe moss has any negative effects on the integrity of your slate tiles but on a low slope it can impede the water flow which can lead to leaking.

A leaking roof can be fixed or avoided by professional moss removal. If leaking has already occurred, offending slate tiles need to be removed, cleaned/scraped, and reinstalled after proper preparation including new sarking under the battens. Moss removal can be accomplished through scraping, pressure cleaning, and/or chemicals but keep in mind that all methods are temporary since regrowth will eventually occur.

Provided your roof has steep enough pitches to prevent these natural growths from impeding water flow, removal is simply a matter of personal choice. Many people prefer the moss and lichen as “character building” qualities that money can’t buy and only time can add. Architects will often even specify mossy reclaimed slates, especially with an extension to match the existing slate roof and home.

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.

Do Hail Storms Damage Slate Roofs?

You obviously want the answer for your roof to be no but we have seen many cases recently where the answer is yes. The determining factor, not surprisingly, is the quality of the slate.

Melbourne has experienced some very intense and damaging hail storms in recent years. Quite a large number of older and softer slate tiles did not fare well in these storms. Damage ranged from only a few perforated or snapped tiles to a need for complete replacement of the entire roof, and everything in between.

There were some instances we inspected where the roofs were relatively new but poor quality tiles were used and the damage was considerable, requiring complete replacement of the roof. Overall though, roofs with concrete or terracotta seemed to sustain more damage than slate roofs did.

There is definitely good news for everyone choosing good quality slate for their roofing. ALL of the roofs we inspected that had good quality slate, both new and old roofs, were completely unfazed. They were undamaged, water tight, and worry free. You could easily say this makes a strong case for choosing good quality slate roofing installed by master slaters.

Can You Walk On Slate Roofs?

The best answer to this question is no. That answer should include other tradesmen like house painters, satellite dish installers, etc.

The problems with walking on slate roofs include both safety concerns and damage to the roofing material.

Safety Concerns

Steep pitched roofs are both difficult and dangerous to walk on. The risk of personal injury is significant. It ought to go without saying but we’ll mention anyway that a slate roofing professional is much cheaper than a hospital or funeral home.

Even lower pitched roofs at 28 degrees or less still pose significant hazards. Melbourne roofs are prone to moisture, moss, and other naturally occurring growths that are harmless to the roof but make the surface slippery. Slippery + slope + gravity = quick trip to the ground.

Roofing Damage Concerns

The quality and age of the slate roofing material is a major determining factor in how well the roofing holds up under human feet. Good quality slate holds up well under everything Melbourne weather can throw at it, but is doesn’t necessarily hold up to foot traffic. Lesser quality slate most definitely caves under pressure.

Without the knowledge a slate roofer has for being on the roof, any attempts to walk on the roof can and probably will result in snap, crackle, pop, perforation, or even dislodging of the slate tiles, along with other potential damage.

Here’s a great way to put this in proper perspective: In 10 minutes, an inexperienced person can do more damage to your slate roof than 100 years of nature could!

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.