Flat roofs are common on commercial buildings and their aesthetic appeal are making them more popular in residential construction, but whether you are a property manager or homeowner you need to know what to do if you experience leaks or damage on your flat roof. Let’s dig into the ins and outs of flat roof repair to give you a better idea about flat roof problems and when it is best to repair your roof or replace it. This article covers:

• Common flat roof problems and how to locate and identify them
• Materials needed for flat roof repair
• How to fix a flat roof
• When to call a professional roofer
• How to know if you need a roof repair or a replacement
• Flat roof repair cost considerations

Common Flat Roof Problems

It’s no fun to discover your roof is leaking. Flat roof leaks though can be especially complicated, and understanding common flat roof problems is the first step in fixing them.   Roof damage can occur for many different reasons, including storms, especially those with large hail, high winds, excessive rainfall, or heavy snows. Other causes of roof damage include wear and tear over time, excessive heat and sunlight, or faulty materials or sub-par installation.   Flat roofs are prone to damage by:

• Drainage problems that can cause water to pool on the roof surface
• Extreme temperatures that can cause roofing membranes to crack or blister, or roofing seams to buckle
• Severe storms or excessive debris build up that can cause tears, cracks or punctures in the roofing membrane
• Building settlement that can cause excessive strain on attached roofing membranes, causing tears and separation

These common problems can cause damage to the flat roofing system and eventually lead to leaks. Proper maintenance and routine inspection can help locate and identify these common problems early. Flat roof repair is always best done when problems are small. Early detection is key to catching small problems and preventing them from becoming bigger ones.

Locating and Identifying Common Flat Roof Problems

Before jumping into how to fix a flat roof, it is helpful to know how to locate and identify common roof problems. Routing inspection, especially by a professional roofer, can help identify a flat roof membrane that is becoming worn or has experienced storm damage, and may require a repair. Getting an inspection after an especially strong storm, a winter with lots of snow, or a summer with excessive heat is always a good idea. Below are some common signs to look for when trying to determine if your roof is leaking and where it may be leaking from.

1. Roofing Membrane Degradation

Membrane cracks, tears, punctures, and blisters are all signs of the flat roof membrane starting to degrade and can cause it to leak. In addition, seams and flashing are especially prone to degradation and damage. Looking at seams and flashing is important because they often prove to be where leaks are originating.

2. Water Collecting on the Roof

Water ponding or pooling on the roof’s surface is a sure sign that something is wrong. It can be a sign that the roof membrane is starting to sag, preventing proper drainage. This can lead to splits or tears in the membrane and water penetration below the membrane surface, causing leakage.

3. Vegetation and Moss Growth on the Roof

Spotting vegetation or moss growing on your roof can also be a sign that water is collecting on the roof’s surface.

4. Interior Signs of a Leaky Roof

Other signs that your flat roof is leaking can be found on the interior of the building. Watermarks on the walls or ceiling of a building can indicate a leaking roof. Walls or ceilings that are damp, collecting condensation, or moldy can also be an internal sign of a leaky roof. A damp or moldy smell in an interior room can also be a sure sign of a leaking flat roof.   If you spot any of these signs on your flat roof or in the interior of your building, it may be time for a flat roof repair or replacement.

Read More: How Long Does a Flat Roof Last? Lifespan, Factors, and Tips

Materials Needed for Flat Roof Repair

Minor leaks on your flat roof can be repaired either by a professional roofer or with do-it-yourself repair kits. The materials you need for repairing a flat roof depends on your flat roofing system. EPDM, modified bitumen, TPO or PVC roofing are all different types of flat roofing systems that require different flat roof repair materials. The first thing you need to know before doing your flat roof repair is what type of flat roof you have.

EPDM Roofing System

EPDM is a flat roofing system constructed from a durable rubber material made from ethylene and propylene. Repairing this type of system is much like patching the rubber on a tire as it is made of a similar rubber material.

Modified Bitumen Roofing System

This type of flat roofing system is made of asphalt combined with durable rubber and solvents. It comes in sheets that are adhered to the roof surface by applying heat through an open-flame torch. Repairing a modified bitumen roof is possible with a self-adhesive heat-applied bitumen flashing tape, or larger permanent fiberglass mesh patches and roofing cement.   TPO Roofing System TPO is a single-ply roofing membrane made of polypropylene and ethylene-propylene rubber that is adhered together with a polymer. It is installed by adhering the rubber membrane to the roofing surface. It can be repaired much like the EPDM system.   PVC Roofing System PVC roofing is a durable, yet flexible plastic material that is layered with polyester to add extra strength. It is installed with heat welding, or adhesives and solvents. Patching PVC roofing is done in much the same way as TPO or EPDM with a PVC patch and adhesive.

How to Patch a Flat Roof

Safety First

Whether you are doing a residential roof repair or a commercial one, safety is the first and foremost consideration. Although a flat roof does not present the same safety issues as a high slope roof, accessing a flat roof, which is often higher up than some high-slope roofs, needs to be done with caution.   Use a sturdy, extension ladder and work with a partner, exercising caution with typical trip hazards. These include loose wires, debris, metal flashing, or uneven surfaces. Also wearing safety equipment, such as waterproof gloves and safety glasses, is a must.

Necessary Tools

Having the right tools is important for any building project. For flat roof repair, the tools you will most likely need include putty and utility knives, a wire brush, a trowel, and cotton rags as well as any specific tools needed to apply repair materials.

Necessary Materials

Use the materials specifically designed for flat roof repair, which include rubberized roofing wet patch, reinforcing repair fabric or fiberglass mesh, flashing tape, and roofing cement or adhesives. The type of material used depends on the type of roofing system you have. Make sure to follow the manufacturer’s instructions. It is also a good idea to have mineral spirits or other cleaners to clean your tools.   Fiberglass mesh or flashing tape is used for modified bitumen roofing while wet patch and repair fabric is used for TPO or EPDM roofing. The steps are similar in that you are cutting away the damaged roofing material and then adhering a patch to seal the area and prevent further leakage.

Steps for Patching a Flat Roof

1. Thoroughly clean and dry the work area before you start. A wet area will not produce a satisfactory outcome.
2. Remove the damaged portion of the roof with a utility knife. Cut out any blisters, bubbles, or cracks. Trim close to where the membrane is adhered to the roof deck. Scrape off the damaged material and then clean the area again before proceeding.
3. Fill depression with wet patch or roofing cement, spreading about 1/8th of an inch over the area with a trowel or putty knife. Take care to smooth it out in at least a six-inch perimeter beyond the damaged area.
4. Cut, set, and embed reinforcing tape, fiberglass mesh, or repair fabric to fit the damaged area and then spread more of the wet patch or roofing cement over the patch and smooth until it is fully covered.
5. Clean your tools with mineral spirits and allow the patch to cure.

When to Call a Professional Roofer

Minor leaks in any type of flat roofing system can be repaired with the right materials, tools, and techniques. If you are comfortable with DIY projects and have the proper materials and tools, it is possible to do the flat roof repair yourself. Hiring a professional roofer to complete the repair is also a good idea, especially if you are not comfortable with DIY projects, as minor leaks can become large leaks, if not properly repaired.   It is also a good idea to call a professional roofer to get a thorough inspection of your roof to ensure that a bigger problem is not going undetected. A professional roofer can read signs that something bigger is happening to your roof deck underneath the roofing membrane that can affect the integrity of your roof. This peace of mind before jumping into a flat roof repair is worth contacting a professional roofer.   If you find that your roof needs replacement instead of a repair or patch, then you will need to call a professional roofer. Contact a roofer with specific experience with flat roof designs and materials as well as one with a reliable reputation.

Flat Roof Repair vs Replacement

It is valuable to know when to repair a flat roof as opposed to when you need a flat roof replacement. Below are a few things to consider when weighing these options.

Size of the Damage

The size of the damage on your flat roof can dictate whether a repair or a replacement is necessary. If the damaged area is small and localized to one area of the roof, then a repair can be successful if done properly. If the area is larger, it may merit a full replacement.

Age and Condition of the Roof

The age and general condition of the roof is also a consideration when weighing flat roof repair versus a replacement. If the roof is fairly new and generally in good condition, then a repair can be a better and less costly option over a replacement.

Condition of the Roofing Materials

If the roofing materials are deteriorated and compromising the integrity of your roof, it is most likely a good idea to have the roof replaced. Patching materials that are deteriorating is only buying time before the roof needs a full replacement. To protect your building, it can be a much better option to replace the roof than repairing it when the repair will not prevent the overall deterioration of the roofing materials.

Flat Roof Repair: Cost Considerations

The size of the damaged area, of course, will affect the cost of a flat roof repair. The larger the area that needs to be repaired the more expensive the repair will cost. The cost of the different materials used on the repair will also weigh in on the overall repair price as well as whether you hire someone to do the repair or do it yourself. On average a do-it-yourself flat roof repair can cost anywhere between $300 to $1200, and sometimes more. Adding labor costs from a professional roofer will raise the price of a flat roof repair.

A Few Final Thoughts on Flat Roof Repair

Flat roofs are common on commercial and residential apartment buildings and have grown in popularity for single-homes beyond a property’s outbuildings. There are many different flat roofing systems on the market today with manufacturers upgrading materials all the time. If you are experiencing or suspect a leak in your flat roof, inspecting it for damage is the first step in identifying and rectifying the problem. It is possible to repair a flat roof, but if the damage is extensive, it can be better to replace the roof in the long run. Understanding the process of flat roof repair is important before hiring a professional to know what your options are in maintaining the integrity of your roof and its ability to protect your property.