Roof Leaks & Other Water Infiltration Problems In Your Home in Costa Rica

I’m frequently called upon to help property owners find leaks that have been permitting water infiltration into their homes and condominiums. The purpose of a roof inspection and report is to identify the source of the water infiltration into the interiors of dwellings and to provide specifications for a guaranteed solution.

Let’s begin by identifying the roofing components that will be referred to in this article.

In North America, the exterior walls and roofs on homes and buildings are constructed like the detail in the diagram below. The roof structure is installed on top of the main beam of the walls, and then sheathing laminates (such as plywood or cementitious laminates) are attached to the roof structure to create a flat deck.

Then underlayment, (such as black tar paper) acts as a moisture barrier, and is applied to the sheathing to prevent the transfer of moisture inside. Then the finished roofing product, (such as shingles or clay tiles) is attached on top of the underlayment.

In Costa Rica there are various types of finished roofing materials installed, but without a doubt, the most common and least expensive are metal laminates, known as “Laminas Undulado”, in English they are called “Corrugated Laminates”.

These corrugated laminates are available in calibers (thickness) 26 (.44mm), 28 (.32mm), 30 (.27mm) and 32 (20mm). Any thickness less than .44 mm is dangerous to walk on and the life expectancy is short, especially near oceans and areas with excessive rainfall. The finished surface of these laminates varies and the manufacturers offer various factory applied colors.

White is the most reflective, and being less than 10 degrees from the equator, this is a consideration to reduce ultraviolet thermal transmission of heat. The caliber 26 is available in white. The thinner products are not available in white and would require painting with expensive anticorrosive paint products.

In order to attach these laminates to the roof structure, they require at least 12 screw perforations per laminate. These roofing screws have rubber washers to help prevent moisture from entering in the screw holes, but this rubber deteriorates quickly with the strong ultraviolet radiation from the sun in Costa Rica.

Once the rubber becomes brittle, all the screw perforations are likely to permit water infiltration. On a roof the size of an average home, there would be approximately 1500 screw holes. You can imagine how much water can enter through this quantity of holes.

Depending on the roof design and the quantity of ridges, hips and valleys, as is detailed in the first diagram above, there are many joints, and these areas are where each metal laminate meets, and this is the source of many roof leaks.

Another type of finished roof material, primarily used on commercial buildings, is known as “Laminas Metalock”; in English they are called “Standing Seam”. These laminates are only available in caliber 26, which is .44 millimeters thick. The advantage to the Metalock roofing material is that it has very few perforations to attach the laminates to the roof structure.

However, most leaks occur where the laminates come together at the joints of the ridges, hips and valleys. In these areas, flat metal laminates, known as “flashings” are cut and installed to prevent moisture from entering underneath, but as with any rectangular building material, the angles and joints are the most difficult to waterproof, as is detailed by the arrows in the photo below.

In order to prevent further water infiltration, the solution is to clean the existing laminates and then apply sealers like Thermotek IBS, and Thermotek Asphalt Sealer to the existing metal laminates.

Once the sealer products have dried, a flexible membrane material, such as Thermotek Chovatek Professional, should be installed on top the metal laminates, over the flashings and into the valleys in order to seal the areas where the water infiltration has been occurring.

The Thermotek Chovatek Professional product is a modified bitumen membrane, also referred to as APP or SBS, and is made from asphalt and a variety of modifiers and solvents. The best method to apply rolls of this material is a heat welding process that adheres the product to the surface of the existing roof surface as well as sealing the overlapping rolls of membrane together to create a seamless waterproof surface. 

The metal roof laminates that are commonly used in Costa Rica are .44 millimeters thick and the new membrane is either 4 or 5 millimeters thick. This additional thickness will provide decades of moisture protection as well as an additional thermal barrier that is very important here in Costa Rica, where we are located less than ten degrees from the equator.

Furthermore, the additional thickness of the new membrane will provide an acoustic barrier to eliminate sound transmission through the roofs and into the inside of the dwellings during heavy rains.

The membrane is available in 4 millimeter and 5 millimeter thickness. I guarantee that the roof will not leak for 8 years when the 4 millimeter thick membrane is installed and 12 years when the 5 millimeter thick membrane is installed.

The membrane installation usually takes no more than one week, depending on the size of the roof and the membrane is available in the colors white and terracotta red.

If you have any questions or concerns about this type of waterproofing installation, send an email to

Costa Rica Homebuilder Tom Rosenberger

Written by VIP Member Thomas Patrick Rosenberger of CostaRicaHomebuilder.com With more than 28 years of homebuilding experience, 18 of which have been in Costa Rica, construction consultant Tom Rosenberger knows the ins and outs of building and remodeling a home in the Central Valley area of Costa Rica. You can contact Tom using his Contact Us page here.

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