St. Louis Flat Roofs

Although particularly popular in hotter climates such as those in the Middle East, flat roofs are found all over the world. In temperate areas like the Midwest, they are most often found on outbuildings, small commercial properties and extensions to residential properties. In such climates, flat roofs present the obvious problem of leaks due to puddles of rain forming on the surfaces, but with correct installation and the right materials, a flat roof can still last up to fifty years.

Flat roofs present the benefit of being remarkably versatile thanks to the abundance of design possibilities. Flat roofs feature a multiple-layer design comprising a waterproof membrane, a thermal layer to help prevent heat from escaping from the building and a roofing deck to provide a base for the upper layers. Roof coverings, designed to protect the property from the weather, may include asphalt, metal sheeting or reinforced bitumen.

Note that a flat roof isn’t always literally completely flat: any roof with a pitch of under 1.5 degrees is generally considered to be a flat roof.

Types of Flat Roof

St Louis Flat Roof

St. Louis apartment building roof top terrace exterior.

Flat roofs primarily come in four different varieties: bitumen, liquid membrane, single-ply or green. Bitumen roofing consists of felt materials or mastic asphalt, and there may as many as two waterproofing layers in addition to a water vapor barrier to stop condensation. This type of roof is suitable for concrete or timber structures.

Like bitumen roofs, liquid membrane designs feature one or two waterproofing layers in the form of membranes made from materials such as polyester, and they are suitable for roofs with internal structures made from either wood, concrete or steel decks.

Single-ply roofing is the cheapest type, but it still presents the benefits of being versatile, lightweight and quite strong, making it a popular choice for garages and other outbuildings. Some single-ply roofing designs may feature a synthetic polymer for waterproofing and may be reinforced with fiberglass, polyester or another durable material.

Finally, flat roofs may also come in the form of green roofs, which combines a flat roof with a layer of vegetation to form a living terrace or roof garden. Although any of the above options may be used for the lower layers of the roof, a green roof requires an additional membrane to serve as a barrier to roots and other layers for drainage, aeration and water storage.

Important Factors to Consider

Flat roofs certainly aren’t suitable in every situation, particularly in temperate climates where the weather poses a constant threat. However, they present both advantages and disadvantages, depending on their application:

.   A flat roof is well-suited for home extensions, such as garages, where you want to have a roof terrace or garden. By contrast, the attic space of a pitch roof is often not suitable for domestic use.

.   Flat roofs are very cheap to install when compared to any kind of pitch roof, since far fewer materials are required. Their cost effectiveness makes them very popular for outbuildings and small extensions.

.   Since flat roofs allow water to accumulate, it is important to regularly check the surface to get rid of any puddles after heavy rainstorms. A buildup of snow can also cause problems by placing a lot of weight stress on the roof.

.   Flat roofs generally do not last as long as sloped roofs, although their lifespan is largely determined by the level of maintenance. A poorly maintained flat roof can last far less than ten years even under normal conditions.

.   Absorbing more heat than pitched roofs, flat roofs can cause the room(s) beneath to be uncomfortably hot during the summer months, although during cooler weather, they can keep rooms warmer.


Flat roofs generally require a lot more maintenance than pitched roofs, although they do present the advantage of being more accessible and easier to work with. The following maintenance tips will help you to extend the life of your flat roof:

.   Ponding is the most common problem associated with a flat roof, and this occurs after heavy rain. When ponding occurs, you’ll need to remove loose debris and water, but if it occurs regularly, you may need to improve drainage.

.   Flat roofs must be cleared quickly after heavy snowfall, since the weight of the snow can cause damage to the surface, and in particularly severe conditions, even damage the structure of the roof beneath.

.   If your roof uses a fastened system, you should occasionally examine it for any loose fasteners that could cause weather to reach the lower layers and damage the structure beneath.

.   Always make sure that gutters and downspouts are unblocked, particularly after heavy wind or snow when detritus and snow can cause ice-dam buildups and other issues.

When to Replace Your Flat Roof

St Louis Flat Roof Replacement

St Louis Roofing Professional Replacing Roof

While a regular maintenance program will greatly increase the lifespan of any flat roof, it will need major repairs or even replacement after some time. If you notice any of the following problems upon inspecting your flat roof, you should consider calling a roofing contractor for further advice:

.   Splitting of the roofing material can occur due to surface stress caused by thawing ice and other issues. Look out for any blistering or splitting on the surface as well as soft and spongy areas saturated in water.

.   If the roof is leaking, the underlying insulation may be waterlogged, and it cannot be left to dry out on its own. Before mold and condensation wreaks havoc for the interior, it will need emergency repairs or replacement.

.   Look out for any areas of the roof where the outer surface is missing. If there is any tar paper or other inner layers of the roof exposed, the roof could develop leaks in the next rainstorm.


Lane House Construction provides a range of roofing services including repair, maintenance and replacement of flat roofs for both residential and commercial properties.