How to Waterproof Flat Roofs Effectively

A flat roof is a unique type of roof in which the roof cover is inclined at an angle of less than ten degrees hence the name. Flat roofs come in a number of different types depending on their design structure and materials. 

Read about the different types of flat roofs by clicking here.

A flat roof comes with many advantages compared to other conventional roofing types among which include: simplicity in design as well as cost-effectiveness in setting up and maintenance. However, flat roofs aren’t without their own drawbacks including them being aesthetically unappealing, or less durable due to more severe exposure to weather elements.

Read more about the pros and cons of flat roofs by clicking here.

The major drawback of the flat roof is drainage; being flat means that there is always a risk of water gathering in paddles on the roof which might compromise the integrity of the roof. Owing to this it’s of the utmost importance that a flat roof is waterproof to make it watertight and impervious to damage by penetration of water.

The process of waterproofing a roof consists of a number of steps which include: 

Roof preparation. The roof is prepared for waterproofing by cleaning it and ridding it of any dirt, dust, and debris.

The next step is to assess the condition of the existing waterproofing membrane if one already exists. A decision is then made of whether to simply patch up the existing waterproofing membrane, or overhaul it. That decision helps zero down on what particular waterproofing approach to take. 

The final step is the application of the waterproofing membrane. Different waterproofing types have different methods of application. The waterproofing material is usually applied in liquid form. It is evenly spread out across the roof and left to dry.

There are a number of methods of waterproofing a flat roof that depends on the waterproofing material used. The choice of any particular type of waterproofing depends on a number of factors including; the size of the roof, scope of work, budget constraints, tastes, and preferences among others. These waterproofing types include the Use of repair kits, sealant, Bitumen, and liquid rubber.

Different methods suit different scenarios.

When using a sealant for small repair works on an already waterproof roof, emphasis is put on the areas of interest, the areas that need patching up. Usually, a brush can be used to accomplish this task.

When it comes to overhauling an existing waterproofing cover or waterproofing a roof for the first time, a larger-scale approach should be picked; using either bitumen or liquid rubber and a paint roller.

Sealant; A sealant is a viscous chemical that when applied dries on a surface leaving a water-tight surface. It is appropriate for small-scale works and thus only used on an already waterproof roof simply under repair. It can be used to seal small holes and patches.  

Repair kits; This is also suitable for a small-scale project for a roof with pre-existing waterproofing. It is also merely used to patch up existing waterproofing. This method is not ideal for waterproofing a new roof.

Liquid rubber; In this case, molten rubber is applied to a flat roof, spread evenly, and left to dried. When dry, rubber is impenetrable by water. This method is ideal for flat roofs that have never been waterproofed and can easily be applied on a wide scale.

Bitumen; Bitumen is a petroleum product with efficient waterproofing properties. When heated, bitumen forms a dark liquid which hardens into a waterproof membrane when it dries.

Pros and cons of waterproofing a flat roof.


Waterproofing ensures the longevity of a flat roof. This is because it makes the roof impervious to dampness and water penetration. 

Resistance to dampness also translates into resistance to the growth of molds and vegetation that might otherwise compromise the integrity of the roof.

Waterproofing mitigates the possibility of roof leakage which might otherwise lead to further defects like leakages in the walls or the interior. 


There are costs involved in waterproofing a flat roof in terms of material and labor. 


Waterproofing flat roof counters the most severe risk of a flat roof which is the drainage risk. Waterproofing makes the roof impervious to water and the risks of dampness or the growth of molds. Before making a decision on which waterproofing method to consider, one should consider the scale of the project, and the condition of the existing roof, then weigh the pros and cons of waterproofing.

Leave a Reply

Start typing and press Enter to search

Shopping Cart

No products in the basket.