Q&A for How to Install Torch Down Roofing

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Question

Do I have to remove the existing torch on a roof that is not that old?

Community Answer

Yes, always remove the old material first.

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Question

I have torch on underlay, how is this fitted - is it torched on bitumen side down?

Community Answer

Yes.

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Question

Can torch down roofing be installed over felt?

Community Answer

It is best to use #75 glass base underlayment. Secure it with roofing nails and then apply the torch down. Priming the underlayment is not needed.

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Question

I have a normal propane torch used for soldering copper water pipes together. Can I use it for torch down roofing?

Community Answer

No. Those torches don't produce enough heat. You need to melt a wide piece of bitumen (6") before rolling it onto the roof. A handheld torch will only melt a 1- to 2-inch spot and will cool before you get to the entire width of the roofing material

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Question

Should I use perforated felt on a warm roof?

Community Answer

Use base sheet. Either a "mop base with poly" or torch-torch. According to the article, the felt is just a fire protector, so mop base will work. Felt will catch fire. The best thing would be peel and stick base with primer. Note: peel and stick only works well in warmer temperatures.

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Question

Do all torch down roofs require three layers of each, or can fewer layers still be efficient?

Community Answer

Not all. If the roof is leaking as it is, you're better off doing a new one; otherwise you're putting bandaids on top of bigger problems. Most manufacturers will only warranty roofs that have 20% moisture inside and two layers. Keep that in mind.

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Question

Do I take the plastic backing off of the felt or will it just melt?

Community Answer

If you're able to peel the back off, it's not torch down. Hire someone with experience. Beginners don't do well at this even with the best instructions.

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Question

On a concrete roof, once I have removed the old torch on the membrane, do I need a primer or do I apply the torch on it directly?

Community Answer

Yes, use concrete primer. Make sure to scrape it very clean. Honestly, it takes a lot of experience to learn how to do this correctly, so I recommend hiring someone who specializes in torch down.

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Question

Why would lumps or bubbles appear on a smooth surface?

Community Answer

Air or moisture. Do not apply on wet surfaces. Air is due too poor installation and uneven heat distribution.

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Question

After completing a flat carport roof, are the nails supposed to show underneath the carport?

Community Answer

No, the nails should not be visible from underneath the roof.

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Question

Can I apply torch on roofing to a metal roof without mechanically fastening the base sheet?

Brett Gilbert

Top Answerer

Instead of using nails, look for base sheets with adhesive backing or use roofing cement. You will need to hold down the sheets to ensure they lay flat, or else the torch down membrane may not seal correctly.

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Question

Can a torch down membrane be installed vertically to a 2% sloped roof?

Brett Gilbert

Top Answerer

It is possible, but try to make use of the slope. Roll the torch down sheeting in the direction of the incline. Take care to use proper safety methods, such as a harness, to keep yourself on the roof.

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Question

What's the average cost for material and installation?

Brett Gilbert

Top Answerer

You might end up spending about $300 USD to install it yourself. Factor in labor costs if you plan on hiring someone.

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Question

Do I have to prime a new sterling board flat roof before laying torch on felt?

Brett Gilbert

Top Answerer

You should be able to attach the felt by stapling or nailing it directly to the wood. The primer will only be necessary for the flashings.

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Question

How can I remove old torch on layers from roof?

Brett Gilbert

Top Answerer

Slice it with a utility knife, then begin peeling it back. Shovels, pitchforks, and hook blades are a few tools you can use to roll the torch down material back.

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Question

Can I use torch down on a modified 90 granulated roof system?

Brett Gilbert

Top Answerer

You can, but take care to ensure the torch down material adheres correctly. Make sure it lays flat against the roof and press down on it before it solidifies completely.

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Question

My region requires ice & water shield. Can torch down adhere to it?

Brett Gilbert

Top Answerer

No, torch down membranes shouldn't be applied over a shield. All you need is fiberglass mesh and flashings, which will seal out the water. Check your region's regulations to see what kind of roofing they recommend.

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Question

What is the typical square footage of a roll of torch down?

Community Answer

Most torch down roofing will come in rolls that are 3 feet by 33 feet, or 100 square feet.

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Question

I am thinking of buying some 6mm torch-down felt that they say does not need an underlay. Please advise?

Community Answer

All torch-down needs a fiberglass base, either porous or all-weather, nailed to code.

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Question

Does the surface need to be dry?

Community Answer

Yes, the surface must be dry before membrane is applied or moisture will be trapped below the moisture. Then, in warm weather where it tries to evaporate, there will be blistering of the membrane.

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Question

Can I put torch down on an RV roof?

Community Answer

This is not a common practice and not recommended. Rubber (EPDM) or plastic (TPO or PVC) are the best choices.

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Question

Would it make sense to torch down the interior overhead of a Greyhound bus conversion?

Community Answer

Not on the interior, because moisture and air could permeate from above. If you had a breach in your bus' roof, now or in the future, the bitumen would prevent the leak only temporarily, causing further damage to exterior sheet metal. Another reason to use a different product on an interior space is the VOCs (volatile organic compounds) that bitumen and asphalt products release, which are known carcinogens.

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Question

Do I need to add the roofing at angles?

Brett Gilbert

Top Answerer

You only need to roll the torch down material in straight lines. When you get to difficult sections, such as at walls and chimneys, you can cut the sheets to the size you need.

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Question

Can torch down be applied below 40 degrees?

Brett Gilbert

Top Answerer

It isn't recommended. The cold weather can prevent the bitumen membrane from adhering to the roof. For the best results, wait if possible.

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Question

What is the best way to install a new torch on roof over the top of an old one? Do I have to remove the old roof?

Brett Gilbert

Top Answerer

You should always remove the old material first so that you get a consistent seal with the new membrane.

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Question

Can torch down be applied over shingles?

Brett Gilbert

Top Answerer

You may be able to get away with it, but you're better off removing the shingles. This will give you a chance to lay down insulation and get a better seal on the new roof membrane.

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Question

Do I need to use nails on the second and third layers when putting down the fiberglass?

Community Answer

As of yet, I have no experience with installation of torch-down roofing, but I would think that either nails or heating the top side of the modified bitumen layer just installed (a strip at a time, so to speak) and rolling out and pressing in the next layer of fiberglass sheet would be required (to hold all six layers together). If the latter method was okay, I think they would have discussed it, so I wouldn't even try it. I'd go with the nails, as prescribed.

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Question

Can I apply torch down on a 6x12 roof?

Community Answer

You can, but it would be more cost-effective to shingle or use another method of pitched roofing.

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