Blog · A Simple guide to flat roofs

1: Flat Roofs Are Not Actually Flat

That’s right — flat roofs usually aren’t flat. A so-called flat roof may look horizontal but often has a slope

Slope and pitch create runoff. Water pools or puddles when there is no slope or pitch, leading to roof damage. You want water to flow into a gutter system and away from the foundation of your home. Flat roofs and low-sloping roofs don’t drain as quickly as it does with other roofing systems.

2: Flat Roof Systems—the Pros and Cons

The flat roof system is often used in commercial and industrial applications here in Kenya

 

Things to consider with flat roofing systems:

A. Added Usable Space

HVAC and refrigeration components are usually installed on the roofs of commercial buildings and other flat roofing systems. This allows more valuable space for building owners.

B.Easier Inspection and Maintenance

Commercial buildings are inspected frequently. A flat roof is easier to inspect and maintain should an issue arise.

C.Improved Energy Efficiency?

Flat roofs may be more energy efficient, depending on the materials used and the location of the building.

 

3: The Downside to Flat Roofs

Flat roofs may be more prone to leaks and hence they demand more maintenance than other kind of roofs.

Proposed Flat Roof

Proposed Flat Roof

 

Leaking Flat roof

Leaking Flat roof

 

 

4: The Types of Flat Roof Systems for Homeowners

There are several flat roof systems available to homeowners:

  • “Rubber roofs”(e.g., ethylene propylene diene monomer, known as EPDM)
  • Modified Bitumen Systems (MBS)

 

Rubber roofs (EPDM roofs)

These flat roof systems contain one layer of rubber or a rubber-type material that is mechanically applied. Adhesive straps are used to secure the rubber-roof systems. EPDMs are waterproof and is relatively easy to install.

An EPDM flat roof

An EPDM flat roof

 

An EPDM flat roof of a residential building in Nairobi

An EPDM flat roof of a residential building in Nairobi

EPDM membranes have a very long lifespan. Some installations exceed 40 years of exposure under various climatic conditions.

 

MBS: The preferred alternative. 

Modified bitumens generally use a traditional waterproofing medium — asphalt — modified with atactic polypropylene (APP), styrene butadiene styrene (SBS), synthetic rubber or other agents that create a uniform matrix that enhances the physical properties of the asphalt. SBS and APP are the most common bitumen modifiers used in Kenya.

SBS (Styrene-Butadiene-Styrene) modifies the asphalt by forming a polymer network within the bitumen. SBS gives the bitumen rubber-like characteristics and improved resistance to aging and weathering. Most SBS-modified bitumen sheets are either set in hot mopping asphalt, torch-applied or adhered with cold-process adhesives. SBS-modified bitumen sheets that do not have factory applied granule or foil surfacing need some form of field-applied ultraviolet protective coating.

APP (Atactic Polypropylene) is a thermoplastic polymer which forms a uniform matrix within the asphalt. This enhances the bitumen’s performance by increasing its UV resistance, increasing its flexibility at low temperatures and improving its flow resistance at high temperatures. APP-modified bitumen sheets are generally applied using a propane-fueled torch. Applicators use the heat to soften the modified bitumen on the underside of the sheet and then cools to form a waterproof adhesive bond.

APP Application on a basement

APP Application on a basement

 

APP Bitumen membrane

APP Bitumen membrane

 

APP Bitumen membrane

APP Bitumen membrane

The application of modified bituminous roofing is a construction process that involves the skillful arrangement of several components as specified for the process. The level of quality in the workmanship during the application process is critical.

 

For technical help:

Phone:   254-02-2358486, 254-20-422949/50

0721-766847, 0734-808052

Email: [email protected]