Nowadays, low-slope roofs are popular for commercial structures, but they are also increasingly showing up in residential architecture. Whether planning a remodel, building a new house, or just wanting to maintain your current roof properly, as a homeowner you must grasp the nuances of low-slope roofs.
From its definition to maintenance advice and common materials, this in-depth blog post will take you through every aspect of low-slope roofs.
What Is A Low-Slope Roof?
A low-slope roof typically looks completely flat but has a gentle incline for water drainage, unlike steeper traditional roofs. It uses materials designed to handle pooling water, making it suitable for different styles and climates. Often used on commercial buildings, low-slope roofs are great for rooftop gardens, HVAC systems, and offer various aesthetic options.
What Qualifies As A Low-Slope Roof?
Any roof that rises less than 2 inches for every 12 inches of horizontal run is considered low-slope roofing, written as a pitch of less than 2:12. Roofs with a slope up to 4:12 can also be classified as low-slope roofs by construction rules.
Common Applications Of Low-Slope Roofs
- Commercial and Industrial Buildings: Warehouses, retail stores, office complexes
- Residential Buildings: Houses, especially in arid climates
- Large Commercial Structures: Big box stores, shopping malls
- Institutional Buildings: Schools, hospitals
- Industrial Structures: Manufacturing facilities, distribution centers
- Hospitality Buildings: Hotels, motels
- Multi-Family Residential Buildings: Apartment complexes, condominiums
Types of Low-Slope Roofing Materials
Let’s take a look at some low-slope roof options for your home:
#1. Single-Ply Membrane
For roofs with a low slope, single-ply membranes are a modern yet efficient option. Commercial buildings can benefit significantly from a single layer of this robust and flexible synthetic material. Modern materials are used to create this membrane, which is UV-resistant, simple to install, and low maintenance.
They can also adapt to varying temperatures, lowering the risk of cracks and gaps from flexing materials. In addition, its waterproof nature reduces the possibility of leaks and water damage. It is often possible to place them over pre-existing roofs, which reduces waste and disposal fees from removing the old roofing materials.
- Cost-Effective: Lower costs for materials and installation.
- Lightweight: Reduces building stress, ideal for commercial use.
- Durable and Weather-Resistant: Withstands harsh weather and temperature changes.
- Easy Installation: Quick application with large rolls of the membrane.
- Puncture-Resistant: Resists damage from foot traffic and equipment.
#2. Built-Up Roofing (BUR) System
Given that they offer a dependable and long-lasting waterproof membrane, built-up roofing (BUR) systems are another popular option for flat or low-sloped commercial roofs. These systems are made of fiberglass or polyester reinforcing fabric sandwiched between several alternating layers of bitumen roofing (asphalt or coal tar). Usually, a layer of small stones, fine gravel, or a reflective coating covers the surface of a BUR system.
- Multiple Layers: Strong water and weather resistance.
- Adaptability: Handles building movement and harsh conditions.
- Energy Efficiency: Reflective coatings lower cooling costs.
- Lower Maintenance: Less upkeep is needed.
- Fire Resistance: Excellent fire safety.
- Customizable Design: Fits specific needs and climates.
#3. Modified Bitumen
Modified bitumen roofing systems are a durable and flexible roofing option made by mixing asphalt with polymers and reinforcing it with fabric mats. It’s a cost-effective choice for flat or low-slope roofs and typically comes in a multi-layer system. There are two main types: APP (more UV-resistant) and SBS (more flexible). It offers good protection but has a shorter lifespan of about 20 years and can absorb heat if dark in color. Proper installation by a skilled contractor is essential due to potential odors and fumes.
- High Tensile Strength: Resists punctures, tears, and damage.
- Excellent Waterproofing: Prevents water penetration and damage.
- Flexibility: Expands and contracts without cracking.
- Resistance to UV Rays: Protects against sun damage, extending lifespan.
#4. Metal Roof
Metal roofs for flat roofs are popular due to their durability, energy efficiency, and modern look. Metal roofs handle flat roofing challenges well, such as water drainage and insulation, and are made from materials like steel, aluminum, or copper. They are lightweight, reduce the structural load, and can be coated to reflect heat, which is great for warmer climates.
- Standing seam metal roofs feature vertical seams with concealed fasteners and a flat area between them. It offers a sleek look, design flexibility, energy efficiency, and durability, lasting up to 60 years. It’s weather-resistant and accommodates thermal movement but can be more expensive.
- Corrugated metal roofs use exposed fasteners and are a more affordable option. They are less weather-tight and durable compared to standing seam metal roofs, but are generally more economical.
#5. Thermoplastic Polyolefin (TPO)
For commercial roofs, thermoplastic polyolefin (TPO) is flexible, long-lasting, and available in huge sheets (10, 12, or 20 feet wide) made of polypropylene and ethylene-propylene rubber.
Thanks to its reflecting surface, which lowers heat absorption and cooling expenses, TPO accounts for over 40% of the commercial roofing material industry. TPO has fewer heat-welded seams for a watertight seal and is simpler to install and maintain. Most options are chlorine-free, 100% recyclable, and resistant to chemicals and UV radiation.
- Durability: Resists UV, chemicals, and punctures.
- Lightweight and Flexible: Easy to handle and install.
- Heat-Welded Seams: Strong, watertight seals.
- Cost-Effective: Lower installation costs.
- Aesthetic Versatility: Available in various colors.
#6. Ethylene Propylene Diene Monomer (EPDM)
The next one, ethylene propylene diene monomer (EPDM) is a durable synthetic rubber membrane widely used for flat roofs. EPDM is popular for its versatility and suitability for commercial, industrial, and residential buildings.
Available in black and white, white EPDM is more reflective, helping to lower heating and cooling costs. EPDM can be installed in several ways—fully adhered, mechanically fastened, or ballasted—depending on factors like the building’s location and climate.
- Durability: Lasts 50+ years with proper maintenance.
- Waterproofing: 100% waterproof and resistant to punctures and tears.
- Flexibility: Stretches over surfaces and returns to shape.
- Weather Resistance: Withstands high winds, hail, and severe weather.
Points To Consider When Getting A Low-Slope Roof
Before installing a low-slope roof, think of the benefits and drawbacks mentioned below.
Benefits of Low-Slope Roofs
1. Better Heating and Cooling
Low-slope roofs have less attic space than steep roofs, which means less air needs to be heated or cooled. This can make your building’s heating and cooling more efficient.
2. Easier to Maintain
It’s safer and easier to walk on a low-slope roof, which helps with tasks like cleaning and repairs. There’s less chance of slipping compared to a steep roof.
3. Cheaper to Install
Low-slope roofs use fewer materials and need less labor, making them cheaper to install. Even if you choose a pricier roofing material, lower labor costs can balance it out.
4. Good for Solar Panels and Green Spaces
The flat or gently sloped design is perfect for adding solar panels or creating green spaces, like rooftop gardens.
5. Extra Usable Space
Low-slope roofs can hold large equipment like HVAC systems and offer extra space for other uses.
Drawbacks of Low-Slope Roofs
1. Slower Water Drainage
Water, snow, and ice can sit on low-slope roofs longer, which might cause leaks and damage if not maintained properly.
2. More Maintenance Needed
With more standing water, low-slope roofs need frequent maintenance to remove debris and prevent leaks. The roofing materials might also wear out faster.
3. Fewer Material Choices
Some materials, like asphalt shingles, aren’t good for low-slope roofs because of the risk of water getting in. You’ll need to use materials like modified bitumen, membranes, or metal panels.
4. Risk of Water Pooling and Leaks
If not designed and installed correctly, low-slope roofs can collect water, leading to leaks, damage, and even mold and mildew. Regular upkeep is important to avoid these problems.
5. Stress from Weather
Extreme weather and freeze-thaw cycles can put extra stress on low-slope roofs, causing them to wear out sooner and need more repairs.
How Does Drainage Work On A Low-Slope Roof?
1. Scuppers
Scuppers are openings in the edge of the roof, often in parapet walls. They let water drain off the roof and into gutters or downspouts. Proper sizing and placement help prevent clogs and ensure water flows effectively.
2. Central Roof Drains
Located at the lowest points of the roof, central drains collect water from the surrounding area, which is sloped towards them. They connect to pipes that carry water down through the building, reducing the risk of freezing in colder climates.
3. Crickets
Crickets are triangular structures that direct water towards drains or scuppers, preventing water from pooling in specific areas. They are often placed around obstacles like HVAC units to improve drainage.
4. Gutters
Gutters collect water draining off the roof and guide it away from the building. Regular maintenance is needed to keep them clear of debris and ensure proper water flow.
Drainage Requirements for Low-Slope Roofs
- Minimum Slope: A roof slope of 2% (about 1/4 inch per foot) is required to direct water to drains.
- Drainage Systems: Use primary drains and secondary drains as backups to prevent overflow.
- Ponding Water: Water that stays on the roof for over 48 hours can damage the roof. Good drainage is crucial to avoid this issue.
How To Tell If Your Low-Slope Roof Needs Repair
When you observe any of the following indicators, it’s necessary to contact a roofing expert:
- Pooling Water: Standing water after rain can mean poor drainage, leading to leaks or damage. Regular checks are essential to fix this.
- Visible Damage: Look for rips, tears, or holes in the roofing material. These can cause leaks if not repaired immediately.
- Flashing Problems: Check the flashing around seams and penetrations. Loose or separated flashing can cause leaks.
- Water Spots on Ceilings: Discolored spots on your ceilings often indicate leaks. Investigate these spots for roof issues.
- Cracked or Loose Membrane: Check for cracks or loose areas in the roof’s protective membrane. This can affect waterproofing and needs prompt repair.
- Age of the Roof: If your roof is nearing its expected lifespan (15-30 years), it may need a closer inspection for potential replacement.
What Is The Best Way To Maintain A Low Slope Roof?
1. Regular Inspections
It’s recommended to inspect your roof twice a year in spring and fall and after storms or harsh weather. Have a licensed professional check for damage like cracks or tears, and fix any problems quickly to avoid further issues.
2. Drainage Management
Proper drainage prevents water from pooling, which can cause serious damage. Keep drains, gutters, and downspouts clear of blockages. If water sits for more than 48 hours, it can harm the roof’s membrane.
3. Debris Removal
Regularly clear debris such as leaves and branches from the roof, as it can trap water and cause leaks. Trim overhanging branches to reduce debris buildup.
4. Address Ponding Water
Ponding water is a common issue on low-slope roofs. Regular inspections help find areas where water collects. If ponding continues, consult a roofing professional to check the drainage system.
5. Repair Blisters and Cracks
Look for blisters (moisture trapped between membrane layers) and cracks from UV exposure or stress. Repair these issues promptly to prevent leaks.
6. Fastener Maintenance
Check for loose fasteners that could cause leaks or wind damage. Tighten or replace fasteners regularly to keep the roof secure.
7. Limit Roof Traffic
Reduce foot traffic to prevent wear on the roof. If access is needed, use walk pads to protect the roofing material.
8. Protective Coatings
Reapply protective coatings as needed for UV protection and waterproofing. Consult a roofing professional for the right type of coating.
Conclusion
Low-slope roofs are cost-effective and offer extra usable space but need specific maintenance. By understanding the basics, materials, and common issues mentioned above, we hope you make the best decisions for the long-lasting protection and value of your home.
For quality flat roofing services in Buffalo, NY, choose OConnor Contracting. Our expertise lies in providing excellent flat roofing services and upkeep to safeguard your business or residential property. For trustworthy roofing services, contact us at (716) 600-7663.
