- Why Do So Many “New” Slate Roofs Fail?
- What Roof Frame Structure is Required for Slate Roofs?
- What Type of Roof Slate Should I Use On My Home?
- What Maintenance Does a Slate Roof Require?
- How Long Does a New Slate Roof Last?
- Can You Walk On Slate Roofs?
- Do Hail Storms Damage Slate Roofs?
- What is Sarking on a Slate Roof and Why is it Installed?
- Will Moss and Lichen Affect My Slate Roof?
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.
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.
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.
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.
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
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.
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.
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
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.
Here’s an example of early slate roofing failure after ONLY four years!
Framing before slate roof installation on new construction
New Del Carmen slate tiles with original terracotta capping preserved
Slate roofs require very little maintenance but keeping the gutters free from leaves and other debris is important
Sarking is an important feature in every slate roof installed by Abardeen
This is a before and after example of and old roof requiring all new slating