When it comes to waterproofing your deck or flat roof, there are three primary characteristics that a homeowner should consider: Waterproofing, durability, and flexibility. Naturally, waterproofing and durability go without saying; however, flexibility is often a factor that is overlooked in lieu of aesthetics. Flexibility is crucial in any climate, but especially so in regions that see a lot of fluctuations in humidity and temperature
Say you have a new plywood deck or flat roof over living space. It is imperative that your space below stays dry. Well, regardless of how solid your deck looks and feels – it will inevitably shift, warp, swell, bow and contract depending on your time of year. Wood absorbs moisture from the air and releases it in warmer/dryer temperatures. In addition to that, wood is an excellent building material for earthquakes and shifting foundations because of its inherent flexibility – why compete with acts of God when you can sway right along with them. For these reasons, the membrane you decide to install to protect your surface and the space below must also be flexible.
Even if your deck surface is concrete, flexibility is paramount in importance – especially in climates that see freezing temperatures in winter. Concrete, as we all know, is rigid and has almost no flexibility. It is still a very sensible and extremely durable material – but as the annals of time take their toll on it and the earth shifts beneath a structure; concrete cracks. This is a result of more than just the building ‘settling’. Concrete is porous, so inadequately or non-waterproofed concrete surfaces will absorb moisture. This will expedite the deterioration of the material and furthermore when that permeating water freezes (and therefore expands) it breaks the bonds that hold the concrete together – making cracks form sooner. While it seems counterintuitive to focus on the flexibility of a waterproof membrane on a rock-solid surface, properly waterproofing your concrete deck will not only prevent leaks when cracks occur – but will also help prevent cracking in general by keeping moisture from penetrating the surface.
So, what should you be looking for in a waterproof membrane?
Well, as you may have guessed by now – flexibility. You want your membrane to move with the natural shifting of your structure – regardless of your substrate. Rigid products like epoxy and poly-aspartic membranes will eventually crack, creating leak risks that can then cause even more damage. So, steer clear. Stick with products like urethanes (Flexstone, Tremco, Masterseal etc.), torch-on asphalt-based membranes, or vinyl membranes like Duradek or Weatherdek (so long as you can live with exposed and occasionally vulnerable seams). Ensure that you choose a reputable brand and always look for CCMC approvals. You get what you pay for in the building-materials market, so there’s no point in rolling the dice when it comes to something as vital as your building envelope.
Secondly, as we also touched on; we want to consider the durability of the membrane. Thicker is often better, so opt for a system that is a minimum of 80 mils. If you want to get technical, explore tech-sheets for the systems you’re considering to see test results for things like abrasion resistance, tensile strength, elongation and fire resistance. It is also worth ensuring that the finished product is UV stable and will not break down or require costly regular maintenance like most tile and all epoxy finishes.
Thirdly, we want our membrane to become one with your deck surface; so, adhesion is also incredibly important. Make sure that you have a product that is compatible with your substrate. For example, most vinyl membranes require good-one-side plywood – if you have a concrete or standard plywood system; maybe vinyl is not your best option. Liquid applied products (urethanes) will adhere to standard plywood and within this family; Flexstone with the use of an epoxy primer will bond permanently to concrete substrates as well. To choose the right material, you must also know your substrate – compatibility is crucial.
Finally – and this one should probably go without saying – make sure that your product is waterproof and will remain waterproof for decades to come. Look for test results that address permeability and elongation to ensure that your surface will not absorb water or crack under pressure.
Within these parameters, you can be sure to have a solid and long-lasting waterproofing system that is worry-free and reliable. Once you narrow down your options to high quality, well adhering, thick, flexible, waterproof and UV stable membranes – you can focus on things like warranties and aesthetics. Just make sure you take care of the important stuff first. There are few things more frustrating than a leaky roof or deck.