flashing from metal roof to asbestos siding

chris allen
Hi there, I am in the process of building a covered deck and I am about to install the roof. I am going to use the snap lock galvanized panels. I went to the metal shop today and the gentleman working there was a little concerned about how I would attach my flashing since I did not remove any of the siding. He suggested I simply take a skil saw with a masonry blade and cut a long thin slot in the siding in order to bend the flashing so it inserts into the slot to make a watertight seal. I have never cut siding before and am a little hesitant to do this. Is this the best way or are there other acceptable ways to attach the flashing to the asbestos siding? I have attached a photo for reference. Thanks y'all.
Nate Libbey
The first thing that catches my eye is the word "asbestos". In normal circumstances, cutting the slot in siding is often a normal and efficient way to do this. But asbestos is another thing. The dust is very dangerous, and in many cases unless an expert is the only one who could cut or remove it. Another way often used is to butt the flashing against the wall, and use roofing grade sealant to seal between the flashing and the wall. This is often not the preferred method, but this situation, it may be the better one. One other thing: are you sure it is asbestos and not hardy board or another cement board system?)
chris allen
Thanks for your fast reply Nate. Yes, it is certainly asbestos. The house was built in 1941. I am aware of the concerns regarding the inhalation of particulate asbestos. I think that as long as I wet the siding down prior to cutting and wear plenty of respiration filtration I should not have a big problem with that. At least that is what I have been advised by others when discussing making limited cuts in asbestos. As long as I can keep the dust to a minimum and protect myself adequately, I think I feel ok about it. I am a little worried that using the roofing grade sealant might be a little too temporary, particularly for my region of the country. We are blessed with plenty of rain, humidity, heat, and winds. I am certainly open to advice, however, as I am quite the novice.
Eric Novotny
An informed customer is the Best Customer!
Wetting will help control the particulate and the asbestos in siding (transite) is not typically the most dangerous and friable types. That being said, you will need to keep the area wet as you continue to make your cut as the depth of the cut will be dry and will create dust. I would also recommend using a saw that has a vacuum (preferably a HEPA vacuum) attachment to help control dust. The reality is that fibercement siding will probably create more lung health issues over its lifetime than asbestos. You sound like you are going to be proactive but protect yourself and any residents. If you have access to a negative air machine, that would be a nice addition as well.
chris allen
Ok I have now purchased my standing seam metal roofing and I am almost ready to begin the job. I am ok on the left side of the roof as I will only be cutting into the siding and have no other surfaces to cross. On the right side, however, the roof for my deck will extend beyond the edge of the house by a foot or so and I will therefore not only have to slip the flashing into the cut I have made in the siding, but I will also have to cross the wood trim at the edge of the house. I think the image attached should give at least a bit of perspective. I am not sure about how to transition from going under the siding to the piece of wood I will have to cross. It is just a piece of 1x6 or similar and I could remove a portion of it if it will work. Or maybe I should make a similar cut as I made in the siding and try slipping the flashing under the wood?
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