Commercial, Mixed-Use and Strata Roof Maintenance in Vancouver, B.C.

How To Do Flat Roof Waterproofing In 5 Steps?(STEP-BY-STEP GUIDE)

How To Do Flat Roof Waterproofing In 5 Steps?(STEP-BY-STEP GUIDE)

Roof waterproofing is one of the best measures to avoid leakage. All types of roofs are prone to leakage and water damage, the flat roofing system is no exception to it.

Flat roof waterproofing is done in several steps. First, it’s cleaning, the application of primer, and locating and fixing minor damages. Applying the roof waterproofing liquid and lastly inspection.

However, there is more to roof waterproofing than just applying the waterproofing liquid. This article sums up the process of waterproofing and offers a detailed guide to choosing a waterproofing liquid. Plus, I have answered some common questions about roof waterproofing too.

Before Initiating Roof waterproofing.

As a roofing professional, I often come across roofs that have undergone waterproofing at least once in their lifetime.

Most of the roofs may have opted for EPDM or torched-down modified bituminous membranes. As these were pretty common waterproofing techniques back then.

Previously waterproofed roofs have the residue of the waterproofing materials still present on them. You need to check if the new waterproofing material is compatible with the existing condition of your roof and previously used materials.

The Best example of this is a roof previously waterproofed with silicone. Silicone does not support any other type of coating as the silicone surface hinders the adhesion.

Equally, necessary is clearing and cleaning the roof surface. Even if your roof is new do not skip this step. Dust, debris, fallen leaves, and other dirt may accumulate on the roof in a short time. The waterproofing liquid needs to be applied directly on the clean and even surface of the roof.

Any sort of buffer between the roof’s surface and the waterproofing liquid may stop the liquid from fully taking effect.

To ensure a perfect application it’s best to get the roof cleaned.

Steps in Roof Waterproofing.

The whole roof waterproofing process can be broken down into five major steps.

Step 1- Cleaning.

The best way to clean your flat roof quickly and efficiently is by pressure washing. Pressure washing will effectively rid your roof of any buffers present on it.

Sometimes this process also reveals areas that need repairs before waterproofing, which were previously hidden beneath the dirt and debris.

Step 2- Application of Primer.

Primer is used on the cleaned roof surface to increase the adhesion between the roof surface and the waterproofing liquid. It also increases the durability of the entire waterproofing process.

This step should be conducted on a dry roof as it considerably reduces the drying time. Roofing contractors also use air blowers or torches to speed up the process.

Step 3- Checking minor damages.

In this step, all the corners, edges, pipes, vents, drains, and other roof penetrations are closely checked for any faults or cracks. If any fault is located then it is immediately repaired before the application of waterproofing liquid.

Step 4- Application of Liquid Waterproofer.

The most important step is the application of waterproofing liquid. Generally, two successive layers of any liquid waterproofers need better protection.

This is the topmost layer in the process of waterproofing and it may or may not be UV stable, anti-abrasive, solar reflective, and anti-static. These properties depend upon the type of waterproofing liquid you select.

Step 5- Thorough Inspection.

All phases of the roof waterproofing need an inspection, right from the beginning to the end. Inspection is necessary to point out errors in any step and correct them immediately.

After the entire process is completed, it’s best to have a thorough once-over of the entire roof to make sure everything is done perfectly.

Know more about the membranes used in flat roof waterproofing.

The waterproofing market is dominated by Acrylic and Silicone waterproofing liquid. It accounts for almost half of all roof waterproofing membranes available in the market.

Both Acrylic and silicone have their advantages and drawbacks.


As for Acrylic membranes, they are cheap and easy to apply. However, it includes multiple layers of coating with fabric reinforcement, which increases the duration of the process. Moreover, acrylic membranes are not compatible with roofs where water stagnation may occur.


Silicone on the other can protect the roof even if water stagnates on it. It’s easy to apply. But, silicone does not support re-coting by any other product. It is a must that the re-coting process should be done by the same silicone waterproofing membrane previously used.

This is a great disadvantage economically as well as labor-wise.

Cost of waterproofing.

The cost of waterproofing consists of two aspects. The labor and the materials used. Depending upon the materials the cost of roof waterproofing differs.

Also, the pre-waterproofing cleaning, correcting any faults in the roofing system, and the time required to complete your waterproofing process, will affect the total cost.

Before starting the roof waterproofing consult your roofing contractor and get an estimate.

Many times property managers or homeowners choose the cheapest available material. Usually, the quality of the waterproofing material improves with an increase in the price of the materials.

Choosing cheap materials may seem profitable at first, but the expense snowballs as the time passes and the material fails to do its job properly. Cheap materials may or may not have a warranty. Plus, the cost of re-coting is usually high.

Good quality materials may cost more at the time of application, but they last longer, and hardly any repairs are needed. The cost of maintenance is comparatively low.


How Long Does It Take To Complete The Roof Waterproofing Process?

The whole process may take about 3-5 days to complete. The time frame may differ depending upon the condition of your roof.

Are There Any Precautions Necessary After The process?

The waterproofing membrane takes 24 hours to dry completely. Do not step on the roof while it’s drying. Click here to read some more precautions.


Roof waterproofing is an essential process for the flat roofing system. I hope this article answers all your questions about the process.

However, it’s best to outsource the entire process to a professional roofing contractor. Who can carry it out from start to end and offer you the peace of mind you deserve.

If you are looking for a reliable and experienced roofer look no more!

Leak Stop is a one-stop destination to meet your roofing-related requirements. We offer roof repair, replacement, maintenance, and inspection services all over GVRD (Greater Vancouver Regional District).

We offer a free inspection to first-time clients. Connect with us TODAY at 1 866 777 0084 for immediate assistance!

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