Flat roofs have become the new norm in Kenya, especially for residential houses and commercial rental flats.
But this type of roof possesses significant water leakages challenge if not well waterproofed during or even after construction.
Water leakages can be extremely inconvenient especially when the water damages the internal ceiling finishes of the house.
Below are some of the ways in which you can ensure that your flat roof remains water tight.
APP (Atactic Polypropylene Membrane)
Ideal for flat roofs with minimal protrusions.
The supply of materials and labour fixing rate for APP membrane is KES 1500 per square meter and in comes with a 10 years of warranty.
The Atactic Polypropylene prevents the bitumen from being deteriorated by extreme weather conditions such as sunlight, UV light or even cold temperatures.
To fix it;
The method involves the laying of another membrane on top of the first membrane to ensure that the roof is extremely water tight.
A polyester career is also used to reinforce the waterproof.
Method involves the following steps;
Waterproofing Liquids
Specialized companies such as SIKA and Dr. Fixit have some waterproofing liquids they offer for flat roof waterproofing solutions.
These liquids can be applied as admixtures during the casting of the flat slab while others can be used as fluid coats in case the slab is already cast.
Admixtures for use during casting are poured into the concrete during the mixing process. Examples of the admixtures are SIKA-1, and BASF Master seal.
Fluid coating methodology involves continuous application of the membrane sludge on the flat roof. It is very ideal for roofs with a lot of penetrations and protrusions.
For fluid coating;
Market rate is KES 1200-1800 per square meter depending on your choice.
Use of Sealants
Unlike membranes which are ideal for whole surface application, sealants are used where there are cracks and / or joints.
Sealants are applied selectively to the affected areas and the following procure is followed;
Use a rate of KES 100-150 per linear meter to estimate the costing.
What to Consider when choosing waterproofing method
The choice of waterproof depends on;
But this type of roof possesses significant water leakages challenge if not well waterproofed during or even after construction.
Water leakages can be extremely inconvenient especially when the water damages the internal ceiling finishes of the house.
Below are some of the ways in which you can ensure that your flat roof remains water tight.
APP (Atactic Polypropylene Membrane)
Ideal for flat roofs with minimal protrusions.
The supply of materials and labour fixing rate for APP membrane is KES 1500 per square meter and in comes with a 10 years of warranty.
The Atactic Polypropylene prevents the bitumen from being deteriorated by extreme weather conditions such as sunlight, UV light or even cold temperatures.
To fix it;
- clean the flat surface of any dirt.
- Next apply a bitumen primer to the flat surface.
- Then fix the membrane with overlaps of 200mm where there are joints.
- Note that the fixing of the membrane involves torch blowing the bottom side it till it gets shiny and then laying the heated surface next to the primed surface.
- Finally install the protective cement and sand screeds over the membrane.
The method involves the laying of another membrane on top of the first membrane to ensure that the roof is extremely water tight.
A polyester career is also used to reinforce the waterproof.
Method involves the following steps;
- Clean the surface
- Apply a primer such as bituseal T5 or primer BF 4.
- TORCHBLOW the first sheet bottom and attach it to the flat slab
- TORCHBLOW the second sheet bottom and attach to the top of the first sheet.
- Ensure there is an overlap of at least 200mm where there are joints or at the ends.
Waterproofing Liquids
Specialized companies such as SIKA and Dr. Fixit have some waterproofing liquids they offer for flat roof waterproofing solutions.
These liquids can be applied as admixtures during the casting of the flat slab while others can be used as fluid coats in case the slab is already cast.
Admixtures for use during casting are poured into the concrete during the mixing process. Examples of the admixtures are SIKA-1, and BASF Master seal.
Fluid coating methodology involves continuous application of the membrane sludge on the flat roof. It is very ideal for roofs with a lot of penetrations and protrusions.
For fluid coating;
- Clean the surface of any debris
- Apply a primer if the product data specify so.
- Pour the liquid waterproofing using a roller or brush as specified.
- Wait for the first coat to cure
- Apply a second, final coat as specified in the data sheet.
Market rate is KES 1200-1800 per square meter depending on your choice.
Use of Sealants
Unlike membranes which are ideal for whole surface application, sealants are used where there are cracks and / or joints.
Sealants are applied selectively to the affected areas and the following procure is followed;
- Clean the joint or crack
- Add primer if specified
- Apply the sealant using a spatula or a caulking gun.
- Ensure the application is even
- Wait for 24-48 hours for the paste to harden.
Use a rate of KES 100-150 per linear meter to estimate the costing.
What to Consider when choosing waterproofing method
The choice of waterproof depends on;
- The roofs drainage and slope.
- Weather conditions of the area.
- Condition of the existing roof.
- Air circulation of the existing roof area.