I have been wanting to replace an existing asphalt shingle roof. The cabin is shaded by pines and hemlock, so the roof naturally becomes covered in evergreen needles, with moss growing on the shingles. I would like to maintain the current look but with a roofing strategy designed for the purpose.
The cabin is located in Ontario, Canada we can get lots of snow load, so it will need to be a light weight green roof. It is a simple gable roof constructed from 2X6's (16"oc) mitred to where they meet at the top. The 2X6s are supported on a 4"X10" beam for the front half of the cabin and are constructed as a boxed gable roof detail for the back half of the cabin.
Here is a photo of the existing roof.
Here is a quick sketch of some of the dimensions.
What I would like to do is to:
1 - remove the asphalt shingle
2 - repair any roof decking that is required.
3 - Lay down a protective barrier, cardboard, newspaper or filter cloth
4 - lay down epdm membrane
5 - lay down a protective layer for the membrane
6 - Allow roof to be covered with evergreen needles, sticks and moss.
I am looking for comments on materials noted above and any potential alternatives. I would also be looking for some installation details ie how to best attach the membrane and different layers.
I'm going to put a flag on this because I'm interested to see what answers people will come up with. I faced almost the exact same problem two years ago, what to do with my 25 year old asphalt shingle roof. Since we have no snow load to speak of, I just put another layer of asphalt shingles on the ones already up there.
The pine needles and the moss give it a nice, rustic look. My house is out in the open, so the wind keeps the roof clear of pine straw.
Hmmm....light weight is pretty subjective when speaking of this roof type. I must also post a disclaimer that any advice you get should be checked by a PE with experience in this field or you must except the potential for a "missed element" that could lead to some form of failure.
A painted on epdm rubber roofing is possibly the fastest and easiest encapsulating method (the next being rubber roof or pond lining) then you can address your eva reveal as your aesthetics dictate, and plant as most 'green roofs' with some low moisture plant like sedum. You could also harvest and 'seed' the roof with growing medium suitable for mosses of a given species from your area that grow in such conditions. The list of 'green roof' botanicals is broad.
There are traditional methods and/or natural but these can all add massive amounts of weight as far as I know of.
I can not speak to the ethics of the companies or the chemicals in these products as well. Here are but a few.
On older asphalt roofing with only a little life left, that has moss growth in all of the cracks, it is important to not disturb the moss until the roof is ripped off. Shingles that are near the end and need replacement will often start to leak when moss is cleared.
Thanks for that tip, I would have assumed the opposite.
I did assume that clearing moss would help a roof that was really too flat for 3 in 1 three tab shingles. I cleaned it off. Bad idea. Not only was there moss, that moss had trapped fine dust. When wet, it created a pretty good seal. There was sleight evidence of moisture before I cleaned the roof. After cleaning, we got some snow. Melting snow creates little dams which backed the water up to the now clear sides. It leaked like a sieve. I tarped it and replaced it during good weather. Just to be sure of causation, I tried this on a few small sections of homes slated for demolition. I got the same result. Moss can destroy asphalt shingles. It must be dealt with regularly and early in the life of the roof. If a roof has already been badly neglected, it's best to leave it pretty much alone. It's OK to remove thick balls of moss from the lower edges of shingles if they are causing water back up. The stuff on the edges is best left alone on older asphalt.
This thread shows how moss can preserve roofs that have a covering of pea gravel. Dale's 53 year old green roof. --- https://permies.com/t/29729/green-building/Dale-year-green-roof --- Same plant --- totally different result.
Here's a copy of my reply to your questions in that thread. --- Sorry for the delay P Lyons. I just now saw this. The only thing I would change about this plan is that I would use recycled, tight weave carpet as the protective layer beneath the membrane. Sometimes as wood ages, sharp splinters can separate and poke upwards. Foot traffic on the roof can force the membrane against hazards. Don't use carpet that has been stapled. You will miss one. Use stuff that used carpet stripping along the edge. This is a free product, so cut out any questionable areas.
If the roof can handle the weight, a very thin layer of pea gravel could be added. Battens 3/4 inch thick, run horizontally across the roof would create little dams that could hold the gravel in place. They won't hold much gravel or water, just enough to prevent the liner from blowing up and to work as needle dams. Hopefully moss will take hold and spread from these moist lines. Dust, bird poop and sticks will accumulate. Don't try to cover the whole roof with gravel if weight is an issue. The 3/4 strip will easily back up a strip of gravel of that thickness at it's bottom edge and becoming progressively thinner going up. The roof will appear to have a dozen little terraces. Walk only on the clear areas immediately below battens where gravel does not gather. Use only nice round pea gravel. A misstep could cause sharp crushed gravel to puncture the membrane.
Don't try to stretch the membrane out. We don't want the weight of the organic layer to hold the membrane in perpetual tension.
I wouldn't glue it except possibly along the edge. weight alone should hold it in place.
Sun is the enemy of rubber. I would rake up plenty of needles and apply them before a rain and during a period of little wind. Moss can be gathered from the woods or from other areas. Try seeding a little. A small amount of grass clippings might help things to get started.
Once it is established, stay off of it. Pop up for inspections regularly, but mostly it should be admired from the ground or from the ladder.
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