How to Waterproof a Flat Roof in Noosa: A Homeowner’s Guide

Waterproofing a flat roof is like giving your home a raincoat. It’s essential for keeping the weather out. This means the health of the entire building will depend on it as the building can’t rely on the natural draining capacities of a slope.

In other words, a flat roof absolutely needs waterproofing. Unlike many other things, it’s more than a mere nice-to-have!

Whether you’re dipping your toes into an entirely new project or maintaining an existing roof, this article will help you figure out how to get it done right. But before we begin, let’s clear the air of a confusion we’re hearing all the time.

A flat roof and a leveled roof are the same thing, different name. Both terms refer to roofs with a very low pitch, often seen on modern homes and buildings. (There is NO such thing as a completely flat roof, by the way.)

Now that we’ve got that sorted, let’s dive into the waterproofing itself.

How to Prep Your Flat Roof for Waterproofing

Think of prepping your roof like painting a room – you wouldn’t just slap paint on a dirty wall. After all, you want it to stick and remain there.

So here’s what you need to do:

Start by giving your roof a good scrub. Sweep away any debris and scrub off any dirt or grime. You’ll want to have a nice, smooth surface for the waterproofing to stick to. To be 100% sure and make things easier on yourself, rent out a pressure washer. It’s the only way to blast away anything that doesn’t belong there: from dried out bird goo to moss or lichen, dust or gravel.

Next, you’ll need to wait until it gets completely dry. In some cases (like liquid membranes), the surface might need priming too to make sure the liquid sticks.

Now that it’s clean of everything that doesn’t belong there, you can inspect your roof for any damage. Look out for cracks, blisters, or other issues. If you spot any, fix them up before moving on. Waterproofing over damage would be like putting a band-aid on a broken leg – it just won’t work.

Finally, check your drainage. Make sure water has a clear path off your roof. If it can’t escape, it’ll find a way into your home, no matter how good your waterproofing is.

Choose the Right Waterproofing Method

When it comes to waterproofing, there are a few different methods to choose from. Each has its own perks and quirks, so let’s break them down:

Liquid Membranes

Think of these like paint for your roof. You brush, spray or roll them on, and they create a seamless, watertight barrier.

They’re great for roofs with lots of nooks and crannies, but they can be a bit messy to apply and might need multiple coats to get it right.

What you’ll need, however, is a pro assessment of whether the surface material is compatible with the membrane itself. Some materials, like silicone, will repel any liquid whatsoever. So the process is more complex and potentially ridden with issues than slapping a liquid onto the surface would suggest.

Pros:

• Flexibility: Liquid membranes can stretch and move with your roof, which is great for handling temperature changes and slight movements.
• Seamless: Since it’s applied like paint, there are no seams or joins that could potentially leak.
• Easy application: You can apply it yourself with a brush or roller, making it a DIY-friendly option.

Cons:

• Curing time: It needs time to cure properly, so you’ll need to keep an eye on the weather to avoid any rain during this period.
• Potentially finicky: Before committing, double check if the roof surface material is compatible with the liquid.
• Messy: Application can be messy, and you might need multiple coats to get the job done right.

Sheet Membranes

Sheet membranes are like big rolls of waterproof material. The installation is simpler than with liquids – you just need to unroll them onto your roof and secure them in place. On the bottom side, they have a self-adhesive layer that will make sure they remain there. They’re tough and long-lasting, but they can be a bit tricky to install around corners and details.

The thing about synthetic materials that these membranes are made of is that you can “stuff” them with almost any added features you’d want. Need them to be more than just waterproof? Just say the word and you’ll get a variety that’s also resistant to flame or absorbs UV.

Pros:

• Durability: Sheet membranes are tough and can last a long time with proper maintenance.
• UV resistant: Many sheet membranes are resistant to or absorb UV rays, which helps them last longer in sunny conditions.

Cons:

• Seams: The seams between sheets can be a potential weak point if not properly sealed.
• Installation: They can be tricky to install, especially around corners and details. It might be best to hire a pro for this job.

Bituminous Membranes

This one’s a classic choice, actually a subcategory of both liquid or sheet membranes that’s made from asphalt or tar. The reason why we’re singling them out in a separate section is that they are the most common. Unlike many others, they can be installed year-round. So completely fine if you only just realise in July that you need to waterproof your roof!

Overall, bituminous membranes are tough and reliable, but they can be smelly and messy to apply. Plus, they’re not the most eco-friendly option out there. Bitumen is a petroleum derivate. So it’s not only a byproduct of fossil fuels, but its extraction and refinement is incredibly dirty as well and oozes lots of greenhouse gases.

The stinky aspect isn’t negligible either. The smell isn’t just annoying (at least to some of us); it can be bad for our health too.

Pros:

• Tough and reliable: Bituminous membranes have been used for ages and have a proven track record.
• Cost-effective: They’re generally more affordable than other options.

Cons:

• Eco-friendliness: Not the most environmentally friendly option due to the synthetic, highly processed materials.
• Smelly and messy: The application process can be smelly and messy, making it less pleasant to work with.

Hot-Applied Systems

Hot-applied systems involve heating a membrane with a torch of some 150-250 degrees Celsius to seal it to the roof. They’re incredibly durable, but they require specialist equipment and knowledge. In other words, no matter how handy you are, this one’s potentially very risky and is best left to the pros.

It’s basically coating, similar to both the liquid and sheet membranes that we discussed above. But the difference is that the “regular” liquid or sheet membranes are cold-applied and, apart from requiring attention to detail around the pipes and corners, aren’t risky to work with.

Due to the riskiness, the labour costs of this method will, of course, surpass the cold-applied liquid. In both cases, you should get a layer of watertight seal. But the heating process reinforces the seal, which is why it’s broadly considered more effective.

However, it’s worth noting that hot-applied systems are generally better for big roofs of commercial buildings. Your average residential home can absolutely make do with cold-applied liquid or sheet membranes.

Pros:

• Extremely durable: Hot-applied systems form a strong bond with the roof, making them very durable.
• Long-lasting: With proper maintenance, these systems can last a long time.

Cons:

• Cost: Can be more expensive due to the more complicated and risky labour.
• Specialist equipment: Requires specialist equipment and knowledge to apply, which means it’s a job for the pros.

Common Waterproofing Issues

Even the best waterproofing jobs can hit a snag. Here are some common issues to keep an eye out for:

• Pooling water: If water’s not draining properly, it can pool and eventually seep into your home. Keep an eye on your roof after rain to spot any standing water.
• Poor adhesion: If your waterproofing doesn’t stick properly, it can lift and let water sneak underneath. Proper prep is key to avoiding this. But also extreme diligence while working!
• UV damage: Some waterproofing materials can break down under UV light. Choose a UV-resistant product to dodge this issue.

Waterproofing Your Garage Roof: A Quick Example

Let’s say your flat-roofed garage has seen better days, and you’ve noticed a few leaks. Here’s what you’d need to do.

First, give the roof a good clean and check for any damage. Like we explained above, fix up any cracks or blisters you come across. Scrub it well and let it dry.

For a simple job like this, a liquid membrane could be the way to go. It’s DIY-friendly and easy to apply with a brush or roller. Just follow the manufacturer’s instructions and make sure to cover the entire roof, paying extra attention to edges and corners.

After the membrane’s cured, check the roof for pooling water after the next rain. If you spot any, you might need to tweak your drainage.

Wrapping Up

Waterproofing a flat roof is a job worth doing right. Whether you go for liquid membranes, sheet membranes, or another method, proper prep and maintenance are key. Don’t let water damage catch you off guard – invest in a good waterproofing system and keep your leveled roof happy and healthy. Your future self (and your wallet) will thank you.

So, there you have it – a straightforward guide to waterproofing a flat roof. Now grab your tools and get to work. Your roof’s counting on you!