Torch on Roof

mattcullen

Hi,

Hoping some of you may be able to advise me on how to torch on bitumen on to an almost flat roofed shed.

My father in law was pretty handy and constructed a shed for me and my other half entirely from pallets. The roof is almost totally flat (only about 2 inches of a slope over 2 metres). The plan was to to lay some plywood on this for a smooth surface, prime the plywood and then torch on the bitumen which we've already purchased (it's the smooth surface type).

Unfortunately my father in law has recently passed away. I want to finish the job on the shed so I've bought the plywood and the primer but I'm not sure where to begin with the bitumen.

I've done some googling but would really appreciate some advice on this specific job.

Do I need to increase the angle of the slope?

Do I need to overlap as with a felt roof?

How do I do the edges? Do I let the bitumen hang over the edge, melt it and tuck under the ply?

I will straight up admit I've never done this type of work before so any advice even if its ''hire someone who knows what they're doing cause youre going burn your shed down'' is much appreciated. Having said that I'd much rather do it myself.

Thanks in advance,

Matt

chris445

This is not an easy job to do and i wouldnt recommend someone without experience try it without seeing it done first. It's very easy to burn right through the bitumen felt, especially if you have bought the thinner stuff thats available.

If you are going to try it, this is how i do it. It will prob take you two men if its your first time.

I think the slope you have will be alright because its only over 2m. At the back and down the two sides nail on some fillet pieces. These slope up the 3 edges to make it impossible for water to flow off here. At the front either put on a gutter which you will let the felt flow into or plant a piece of 2x1 onto the soffit flush with the top of the ply to form a drip. the next step is to make sure you prime everything with a bitumen primer. Now roll out the roll of felt and cut it to length, making sure to cover the outside of the fillet pieces and I'd prob go about an inch or 2 below. Also make sure you come about an inch below the 2x1 on the front if you are forming a drip.

Next lay the felt in the exact position and roll it up tightly at each end untilit meets in the middle. Now the second man comes in. while one person heats the felt the second uses a piece of timber to roll it out. This is where the experience comes in though because if you heat one area too much you are likely to burn through the felt. Maybe try it out on a few strips before the actual job to get a feel for how much it has to be heated to stick properly.

Once you have half of it stuck down go back to the middle nd ensure thefelt is rolled back as far as it can go and start the other half of your strip. I like to felt so the lines of the joints run down into the gutter but if you want to go accross the way make sure you start at the front and work back. Each stirp of felt should overlap the last by 100-150mm (4-6 inches).

once you have your roof felted grab a trowel with a rounded top(not too sharp). Heat the joints n the felt and heat the trowel with the torch. I usually do the 2 at the same time by holding the top of the trowel in the flame while heating along the joint(be careful not to apply too much heat and burn the felt). Now run the trowel along the joint and create a seal.

The final step is to apply the 'solar paint' to protect the felt from the hot weather(if there ever is any).

Hope this helps and good luck if you give it a go.

mattcullen

Chris,

I really appreciate you taking the time to offer this detailed (and customised!) advice.

I just have a couple of further questions if you get a chance:

With regard to the fillet pieces, I'll probably be shot for asking this (!) but do you mean strips of thin timber/ply or of the bitument itself?

When I run the bitumen an inch or two below the edge I'm wondering how I'll fix it to the underside?

Thanks Again,

Matt