Torch down roofing, which is also called “torch on roofing”, is a common roofing solution for flat roofs and even for those that are slightly sloped. It may not work in homes that have steep-pitched roofs. The name comes from the use of an open-flame propane torch that is used on many modified bitumen membranes. The modified bitumen sheets are rolled out first on the roof during installation. A hand-held propane torch is then used to heat the material and adhere to the roof surface. The seams are melted together once the layers reach a certain temperature. This unique installation method gives the roof a watertight seal.
Each membrane has a few layers that are made of different materials. The main material is modified bitumen, which is present in the second and fourth layers. The bitumen is mixed with rubber or plastic.
- APP or Atactic Polypropylene – This is a type of plastic. It is flexible to withstand both low and high temperatures.
- SBS or Styrene Butadiene Styrene – This polymer is synthetic rubber. This too is flexible but the melting point is lower compared to APP. So, it works for torch down roofing, cold-processed roofing, and self-adhering. This is a good option for places where the temperature can be low.
The bottom layer may also have a thermo-fusible film, which is a layer of reinforced polyester. The top layer can have granulated materials.
What Is The Cost Of Installing Torch Down Roofing?
How much it will cost depends on the components and labor. Generally, it will be more expensive compared to installing an asphalt roof. It used to be cheap only a few years back. Liability insurance for roof workers, who must work with open flames, has made it more expensive.
On average, the cost to install torch down roofing for a square foot will be between $4 and $7.50. If your roof is 1,000-square-foot, the cost may vary between $4000 and $7500. Apart from the material used and labor charge, there will be other determining factors like the size of your roof, the number of roof layers, and even the season when you are installing.
Two-Layer & Three-Layer Torch Down Roofs
These roofing systems come in two types:
- Two-Layer Torch Down Roofs – There is one base sheet and one smooth cap sheet.
- Three-Layer Torch Down Roofs – It has the same base and cap sheets. It has an additional cap sheet where the surface is granulated.
It costs less to install a two-layer torch down roof, but the three-layer variety is more long-lasting. The granulated cap layer makes the roof fire-resistant, more durable, and also energy-efficient.
Torch Down Roofing Advantages
- Water resistant – The job of a roof is to keep the water away. This is difficult for flat roofs, especially in places with heavy rain or snow. The torch down technique with its waterproof membranes and heat-sealed seams makes the roof more water-resistant. Water won’t get collected on the roof. It will drain off easily, protecting the structures and preventing damage.
- Flexibility, durability – Torch down roofing is extremely flexible. The modified bitumen sheets will expand and contract with temperate changes and won’t crack or split. This flexibility will make your roof more durable. Many roofing materials are damaged because of the changes as they are rigid. The thickness of a torch down roof is also consistent across the roof’s surface.
- Energy efficient – The roof will protect your home from heat and UV rays, particularly when a three-layer roof has a cap layer. Your cooling bill will be lower in the hot months.
- Lifespan – This type of roof can last for 15-20 years. It is more long-lasting compared to most other flat-roof systems.
- Fire resistant – Add the granulated cap layer and your roof will also be resistant to fires.
- Repairs can be done easily – You can carry out repair works easily as the rolls can be sealed quickly. The repair work is also less expensive and less intensive.
Torch Down Roofing Disadvantages
- Fire hazard – There can be some fire hazard because of an open flame. Modified bitumen is fire-resistant. But it can become flammable if it overheats during the installation. Other flammable materials like dry foliage and the wood frame of a house can increase the risk.
- Seam failure – There can be a roof leak if the seams are not sealed properly. This is more common with the two-layer torch down roofs. The problem can be fixed quickly.
- Trapped water – Water can get trapped between the rolled roofing layers during installation or repairs. This is why it is best to do it in the dry season.
- Tears and scruffs – A torch down roof is durable and flexible. But there can still be tears and scratches. The roof system won’t work well if the waterproof seal gets scuffed or torn. You can avoid this by regularly inspecting the roof and doing maintenance work.
There are many advantages of torch down roofs but remember, the installation process is labor-intensive. You will also need skilled roofers. You cannot install the roof independently – it is not a DIY project. Often, it is best to hire a professional for a home remodeling job.
Torch down roofing won’t work for roofs that have significant slopes. It is good for slightly pitched roofs with a pitch between ¼:12 and 1:12. You will usually see them in multi-story apartment buildings and flat-roofed commercial buildings. This will be a good solution if you are looking for a reliable and durable solution that will work for a long time.