Metal roofs are ubiquitous in industrial estates and rural belts. It is cheap to get and easy to install. But they require repair quite frequently.
Note: This article is about METAL Roof waterproofing. If you are looking for waterproofing your concrete roof or terrace, click Here.
Below are major reason why metal roofs need repairing:
Metal corrosion: Due to contact with rain and dust, corrosion becomes a common phenomenon in most metal roofs. Some roofs have precoats or paints which saves it for sometime but eventually succumb to corrosion.
Metal Expansion: High metal expansion and contraction over time, leading to loose fasteners and cracks in seals and joints. These cracks and loose lead to dripping of water inside.
Condensation: Condensation forms when warm, moisture-laden air hits a cold surface. In the case of metal roofs, it happens when warm, moist air from inside the house is driven into, and trapped inside of, the cavity beneath the roof. When the metal roof's temperature drops at night, the air condenses on the underside of the roof.
Storm damage: Due to high speed of wind, metal roofs get damaged and develops cracks. Also, the joints get damaged due to the same.
Leaks due to the sub-standard waterproofing of joints and connections or poor installation (Inner gutters, sky-lights, Exhaust outlet etc.)
Although traditionally many methods using bituminous or coal tar were used for Terrace waterproofing, new generation methods are safer and sturdier.
There are two major type of waterproofing techniques available for waterproofing of metal roofs:
Roof Repair with Single Ply Membrane
Roof Repair with Liquid Membrane
Let us talk in details about the above two methods.
METHOD 1: Single Ply Membrane Technology:
This method uses rubber sheets or polymer sheets which can be attached to the roof mechanically using fasteners or glued with adhesives. It is simple yet highly reliable method to protect your metal Roof.
How to fix membranes on the roof:
a. Ballasted (Putting weight on the membrane)
b. Mechanically Fastened
c. Glued with adhesives
To joint the seam between the membrane, we either use hot air gun (In case of TPO) or joining tape (In case of EPDM).
What are the Advantage of Single Ply Membrane Technology?
Proven track record (50+ years)
Easy and Quick Installation
UV Reflection or Heat retention
Class-A fire rated
Moderate cost
What are the Disadvantage of Single Ply Membrane Technology?
Strength of the membrane deteriorate with time
Joints or seams which have been connected using hot air or tape are vulnerable to debonding
Membranes are vulnerable to puncture
Let us discuss the two type of membrane in more details:
A. Thermoplastic Polyolefin (TPO)
It is a type of polymer single-ply membrane that employees thermo-welding (hot air gun) to joint the seams. This type of membrane was first developed in the 80's and it is currently the fastest growing membrane tech. Almost 60% of the Single Ply Membrane work is being done by TPO.
Dimension details:
Sheets are typically 6-10 feet wide, 20-100 feet long. Thickness of the membrane is ranging from 0.5 mm to 3 mm.
Application:
As the color of TPO is white, it is UV resistant and helps in making building efficient.
B. Ethylene Propylene Diene Monomer (EPDM)
EPDM is a older technology which is black in color and are not UV resistant. Their dimension is similar to TPO. Only disadvantage is that they aren't UV resistant but preferred in colder climate where heat retention is preferred over heat reflection.
How to maintain roof with TPO or EPDM membrane?
It is easy to repair damage in the membrane. Just use a patch where the membrane is damaged. For any inaccessible location, use silicone guns to fill gaps.
EPDM is said to have longer life compare to TPO.
METHOD 2: Use of Liquid-Applied Membrane (LAM) coatings:
When dealing is uneven metal surfaces, sprayable or brush applied liquid coatings are preferred. LAM is very efficient with short application time.
New-age low-odor LAM technology enables installation even in populated urban areas, where hot coal-tar application is prohibited, and for buildings that need repair while still in use without the need to close down the facility (Government Office, Hospitals or Schools).
Example of material that can be bought from market:
There are many option such as Sika SikaElastic or Dr. Fixit 646 Cool Roof Coating for metal roof. Application of above product is easy and availability is also good in Tier 1-2 cities of India.
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