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Steep pitched living roof.

 
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kids building homestead
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Hello all! another forum stalker coming out of the woodwork here.

So making a long story short I'm a single dad trying to start over and build a place for my two kids and my self to live with a very limited budget. I'm making a peg and beam/Hay/cob hybrid. and to top it off... (pun intended!) I want to do a living roof.

I'm wanting a steeper pitch then 35*. which I reading is already hard to contain the soil at this pitch already. I know that anything with a higher pitch will start losing practically. but I'm wanting to get as close to 55* as I can for my loft space. I want the earth roof as I'm told it really helps to keep the roof warm helps lower the amount of insulation you need to add. I need a steeper roof as in the winter time where I live it often times will rain and then drop below freezing at night in the winter, I've been told that a green roof froze over can quickly destroy your roof/house? another one of many reasons I want a green roof is to keep a lower profile when it comes to overhead traffic.

So this being said. I thought of just adding new layers of chicken wire metal/plastic down every year or adding a "ladder" of ripped down trees to help hold the soil down? I also can't find any solid information on what plants could hold up in such a steep pitch.  I'm assuming that with my forest dirt and a steep run off like that would leave me with a rather dry soil. so maybe arid plants?

*side note* I get about 50 inches of rain a year.
Give me some food for thought. I'm starving!



-Ozarkcraft
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master pollinator
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Welcome. If you go into Google Images with a search for what you're looking for it will either be there or it won't. If it's not, there's probably a good practical reason for that. I've never seen a green roof that's very steep. I imagine it could be done in a series of steps, and that would be an expensive way to go.
 
pollinator
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Location: Victoria BC
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If moss is happy in your environment, I would focus my efforts there. It can grow on vertical surfaces without much grip, if there is enough moisture and not too much sun...

But... how to keep sliding snow from ripping it off the roof? Retaining snow seems kind of counter to the purpose of a steep roof, but perhaps necessary to retain moss..

This isn't going to do much for thermal mass in the roof. Frankly I think this is better addressed inside the building unless you reconsider the pitch...
 
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Found this recently:

https://insteading.com/blog/green-roof-inspiration/

Though there are other possibilities, so far evergreen sedums appeal most to me.  Some remain evergreen in snow.  Some bloom.  There are a variety of heights and colors.

With chicken wire in place, and some scattered small rocks (maybe between a couple layers of chicken wire?)  here and there to help keep soil in place and for sedum to grow with, it might be possible to use less soil and get a good insulation result.

If not sedum, there are similar groundcovers.  May help to check the extension office website for your area.

Afterthought.  If a breathable cover/barrier were laid down first, then chicken wire, then a thin layer of small rocks/medium gravel?, chicken wire again, rocks, then plants.  Small pockets would be created where soil can settle in on top of the rock.  Rain would drain through the rocks easily, while the rest could be held down by another layer of rocks, soil, and an evergreen ground cover that grows to maybe 1' or 2' high.
 
O Craft
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If moss is happy in your environment, I would focus my efforts there. It can grow on vertical surfaces without much grip, if there is enough moisture and not too much sun...

But... how to keep sliding snow from ripping it off the roof? Retaining snow seems kind of counter to the purpose of a steep roof, but perhaps necessary to retain moss..

This isn't going to do much for thermal mass in the roof. Frankly I think this is better addressed inside the building unless you reconsider the pitch...



I have thought about the moss. I have a friend that did a hunting cabin with a moss cover on the roof. But I agree that there isn't much insulation added on it's own.

That's the only turn off I have with moss. It grows all over my woodlots. so I'm sure that it wouldn't be hard to get a cover going if I wanted to.


Catherine Windrose wrote:Found this recently:

https://insteading.com/blog/green-roof-inspiration/



That's some good stuff. lots of links! thanks!

Good idea about the rocks. that might work. rocks wouldn't move much I don't suppose if they where held down. I could have sworn I seen something about rocks before but in the context they had it laid out it made no sense to me.  And I don't know why but I never even thought of evergreens... You just shook my world. I have only been thinking of grass like plants until now!
 
gardener
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Those are some cool roofs, but  the texture of a living roof would seem to collide with the purpose of   a steep pitch.
Some of the roofs from the  link are located in places with heavy snow load , but not most of them.
To have a safe green rood, you have to build for the weight. If its not going to shed snow, you have to figure in that weight as well.
That's a lot of extra engineering/materials, for little gain, as green roofs are not very good insulation.


Light weight insulation material and/or building a heavy duty flat roof deck seem like better uses of resources to me.
A steep pitched roof could be infilled with light clay straw, rockwool, or papercrete.
A heavy duty flat roof deck could be easily accessed so the green roof could be a crop of some kind, plus your loft could have more head room, or even become a full story.

One scenario where a steep pitch might work really well with a green roof is on an A frame building.
A set of "stair steps" running  perpendicular to the slope, filled with your soil mix, would let you walk up the side  the building to tend to your roof garden.
You would still need a very  robust roof  structure , but it would be accessible for dealing with crops.
 
Dillon Nichols
pollinator
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Location: Victoria BC
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My parents old flat tar and gravel roof was a de-facto green roof due to moss and sedums. No soil or moisture retention beyond what a few low spots would naturally collect for a while.

The sedums were tough, and pretty. The roof lasted a LOT longer than it was supposed to. They replaced it at perhaps 45 years since construction after very few problems; they wanted to use thr type of roof, but couldn't find a contractor who could/would install one.

I will absolutely use sedums when I do a green roof.. it will be a low pitch, lightweight roof, and I am mostly going to do it because I was gifted some low pitch trusses..


Buut... I am pretty confident sedums would not adhere nearly as well as moss on a steep pitch.

It really is not a coincidence that steep green roofs ate uncommon. The material cost needed to provide the strength could build a larger building with a lighter weight roof and more insulation that would outperform the green roof.

Intensively planted, ie heavy, green roofs offer little thermal advantage unless the climate is just right, with big swings daily that average out near a comfortable temperature. Basically, if you need serious insulation, Inwould really prefer the mass on the inside of it. The uninsulated thick brick walls that worked well in my dad's childhood home in LA, would be incredibly ill suited to Vancouver Island...


As far as unobstrusive goes..

Ariel imagery tends to come from certain angles. Staying under heavy tree cover is made more effective with this in mind. My parents new flat roof is light grey, and depite being around 80ft by 35ft the house is not visible at all on google earth due to trees.

Dark colours, irregular outlines, splotches and curves help; rectilinear shapes grab the eye as building... but a bright coloured pickup or a few white wrapped haylage bales sitting out are much more visible than the dark green or rust roofs on most of my farm buildings, with no deliberate camo at all!

 
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Why not just add another storey to get the extra space?
 
O Craft
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Graham Chiu wrote:Why not just add another storey to get the extra space?

 

Well I'm building this with raw red cedar timber poles. And I'm limited to how many I have that would support a 2th floor and the earth roof. And I'm trying to avoid vertical joints. I never done vertical joints with peg and beam. And I'm not totaly confident in my joint notching abilities for vertical post to be honest.

My cob at first is going to be more of a thin non-load bearing siding on my walls. Much like lathe and plaster. *edit* so the post how im planting will almost be free standing. Only tied in by the roof beams

I have given it a good bit of thought while diging out boulders with my pickaxe today, about adding another full floor and making it a "tower house" with a lesser pitch but I'm unsure.

(One of my pebbles I dug out)
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Location: Kansas Zone 6a
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There are geo textile products that will hold dirt and sod at close to those angles.  Not cheap and would need serious structure behind them, as they shine they have solid earth to hold them in place.  But I have seen them used on bermed and underground houses. Then planted with low ground cover.

Blown cellulose insulation is CHEAP, green and easy DIY if you build with it in mind.  Build with enough attic space to get the insulation deep enough at the edges.  You need large overhangs to protect the cob so that shouldn't be a problem.

 
pollinator
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Dillon Nichols wrote:If moss is happy in your environment, I would focus my efforts there.



If moss is not happy in your environment, creeping junipers are a drought-tolerant substitute. Often used for cascading rock gardens. Usually you can find tons of them in the discount section at your local nursery. Mix and match yellow, blue, and green varieties so the haters can scoff at your sassy scandalousness. https://www.monrovia.com/plant-catalog/plants/1677/blue-rug-juniper/  https://www.monrovia.com/plant-catalog/plants/1702/blue-star-juniper/
 
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