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Is lime wash bad idea for rainwater catchment roofs?  RSS feed

 
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I build brick masonry roofs and catch the water.  The roofs are surfaced with a clay/sand/lime plaster and then lime washed.   Is there any negative affects to the water other than it could become harder?    Seems that  most ground water percolates through limestone .

And if you are interested this lime-clay plaster works better than a sand cement plaster, which cracks and allows dampness.
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Posts: 601
Location: Central Virginia USA
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Just some idle thoughts about the issue

seems like it would be ok  but the real test would be to measure the ph of water in the tank.

Some people  even pay extra for alkaline water, and I believe some of that has calcium added.

I suppose different LW mixtures would have different amounts of lime washing off.

Rainwater tanks sometimes have a lime stone block added specifically to reduce the acidity of rain water, and or to precipitate out heavy metals.

My personal belief however is that highly mineralized water is bad for the body--not so that it would kill you right away but more in the sense of calcifications clogging kidneys, building bone spurs, etc.

So while you can get away with it for bathing and such,  I would use an  RO  filter for any rain water for drinking and cooking

plumbing  deposits might also become an issue at metal fittings and hot water tanks
 
Posts: 315
Location: Amtkel – Abkhazia · 400m elevation · temperate climate
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We have very hard tap water here (lots of limestone in the ground). The plus side is that it does not dissolve copper pipes.
The downside is that it builds up everywhere. Heating it up accelerates this greatly, which is the reason, we don't have an electric boiler anymore.

The roof looks amazing! I have to try lime-clay myself.

If I had to neutralize this water, I would probably build a small pond/bog with clay and a lot of plants and have a slow input of the alkaline water into it.
The plants and bacteria should neutralize the lime (I hope).
 
pollinator
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Location: Ashhurst New Zealand
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Hi Erik - I've been working with different lime plaster variants but haven't tried adding clay to the mix. What sort of proportions do you use, and have you added pozzolans of any sort? It looks fantastic in the photos. How often do you limewash it?
 
Erik Rowberg
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Sebastian Köln wrote:We have very hard tap water here (lots of limestone in the ground). The plus side is that it does not dissolve copper pipes.
The downside is that it builds up everywhere. Heating it up accelerates this greatly, which is the reason, we don't have an electric boiler anymore.
).




Thanks Sebastian this is helpful.

erik
 
Erik Rowberg
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Phil Stevens wrote:Hi Erik - I've been working with different lime plaster variants but haven't tried adding clay to the mix. What sort of proportions do you use, and have you added pozzolans of any sort? It looks fantastic in the photos. How often do you limewash it?



clay- sand- lime- wood ash   4-6-1-0.25

wood ash we just started using on the last roof.

i am adding limewash every year for now.
 
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Would you be interested in explaining your process with a photo essay on ferrocement.com ? There's a contact button there.

Garrett, the web caretaker
 
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Location: Denver, United States
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This is a VERY common practice on islands such as Bermuda. They use the lime on roofs to purify the rainwater since they are so dependent on what falls from the sky for their freshwater supply. You might want to check out  how some of those places put this in place. They are the experts!
 
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Location: Baja Arizona
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Judging by the look of the vegetation around the home it appears that the soil there is somewhat acidic.  If you were to use the water to irrigate, the alkalinity that the rain water picks up from the roof will be largely neutralized in the soil.  If you live in an area with soil that's already alkaline, your soil could become so alkaline that crops may perform poorly.  If the water is used for drinking and bathing you might see a chalky development in your skin and hair that becomes more unruly.  Could lead to kidney stones as well, unless you take dietary steps to avoid these things.
 
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Very nice roof there , well done . Just curious about how you made it ie the structure did you use wood profiles and whats under the lime wash is it clay or cement .
I think lime wash on walls has a great look too and is mildly antiseptic and is porus so better than portland cement . Might want to get your water tested at a lab before you drink it , we use our roof water off clay tiles for chores etc but not to drink, birds on roof equals droppings etc !!!. Our water goes to a brick cement lined settling tank first and mostly we boil or heat the water through a gas boiler before use , Never for drinking .
 
Garrett Connelly
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About drinking rainwater with bird poop maybe on roof.

What should one do about breathing dust with dried bird poop in the air via walking feet or rolling car tires?
 
Erik Rowberg
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Garrett Connelly wrote:Would you be interested in explaining your process with a photo essay on ferrocement.com ? There's a contact button there.

Garrett, the web caretaker


yeah but i get stuck on your signup page.

 
Erik Rowberg
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Garrett Connelly wrote:About drinking rainwater with bird poop maybe on roof.

What should one do about breathing dust with dried bird poop in the air via walking feet or rolling car tires?



First rain filters.  
let the first part of a rain go into a bypass system.  
 
Erik Rowberg
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Malcolm Thomas wrote:Very nice roof there , well done . Just curious about how you made it ie the structure did you use wood profiles and whats under the lime wash is it clay or cement .
.



We dont use formwork as long as we have a vertical wall to start from.  Bricks are 'glued' up with sticky clay  Capillary action from dry brick helps ( no proof).

scroll down to the bottom on this link below
http://alternativebuildingtz.blogspot.com/2016/04/maize-storeage-shed.html

a youtube
https://www.youtube.com/watch?v=ueILoglbAhE


under lime wash is clay-sand-lime-ash  mixture.   Will not go back to cement plaster, had so many problems






 
Garrett Connelly
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Hello Eric,

There is no sign up page at http://www.ferrocement.com No requests for donations or advertisements, either.

ferrocement.com has been gratis world wide since 1999. Book sales paid the way in the early years before everyone had computers.

Water tank rainwater page is also gratis http://ferrocement.com/tankBook/ch14.en.html all ideas are welcome via email.

 
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 I made a boat planter and I used a cement sand clay mix to waterproof it.  so that the bottom of the planter holds water for the plants.  It took a few years to find a cement sand clay mix that did the job,  so I like that you give a mix with lime in it. because any hairline cracks might seal themselves due to lime dissolving in the slowly leaking water    webpage      

Erik Rowberg wrote:

Phil Stevens wrote:Hi Erik - I've been working with different lime plaster variants but haven't tried adding clay to the mix. What sort of proportions do you use, and have you added pozzolans of any sort? It looks fantastic in the photos. How often do you limewash it?



clay- sand- lime- wood ash   4-6-1-0.25

wood ash we just started using on the last roof.

i am adding limewash every year for now.

 
Erik Rowberg
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Brian White wrote:  I made a boat planter and I used a cement sand clay mix to waterproof it.  so that the bottom of the planter holds water for the plants.  It took a few years to find a cement sand clay mix that did the job,  so I like that you give a mix with lime in it. because any hairline cracks might seal themselves due to lime dissolving in the slowly leaking water        



yeah i am so much happier with lime results than cement.  From what i understand cement-clay is not a good idea anyway.
 
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Location: Bendigo , Australia
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An interesting topic, what draw you to build these roofs in the first place?
 
Erik Rowberg
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John C Daley wrote:An interesting topic, what draw you to build these roofs in the first place?



Originally i was looking for cheaper and better alternative to wood truss and corrugated iron that is the norm here.  No need for ceiling board, rodent proof, quiet in rain, etc.  Then i got into flatter vaults, then cross vaults.  so have built a number of buildings this way.
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Phil Stevens
pollinator
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Location: Ashhurst New Zealand
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Even more impressive with the front elevation shot, Erik. I'm full of questions again. Is the masonry reinforced with steel? What are the seismic risks in your area? And have you experimented with timbrel vault construction?
 
Erik Rowberg
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Phil Stevens wrote:Even more impressive with the front elevation shot, Erik. I'm full of questions again. Is the masonry reinforced with steel? What are the seismic risks in your area? And have you experimented with timbrel vault construction?



Phil this is a different building.  http://alternativebuildingtz.blogspot.com/2013/08/groined-vault-house-update.html  
I plastered cement over it with some weld mesh in the plaster.  i did that hoping to keep cracking down.  Other roofs have no steel except in the ring beams.  


We live in the rift valley.  Had a 5 quake a few years ago 100km from here that shook everything.    Not convinced vaults are unsafe in seismic areas.  

Yes have done some timbrel vaults and one stairs.  
http://alternativebuildingtz.blogspot.com/search?q=catalan

http://alternativebuildingtz.blogspot.com/2013/07/first-timbrelcatalan-vaulted-ceiling.html

 
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I grew up in Oregon, which has quite acidic water.  A couple years ago, we moved to the inland desert of southern California.  The water here is extremely loaded with calcium.  We have an electric kettle, and the process of heating water to boiling precipitates out the calcium.  There are large flakes on the bottom that we wash out periodically.

One of the houses we stayed at had water so "thick" it felt like soap when we showered.  We used a Propur filter there for drinking water. It's a ceramic gravity filter. At that house with the "thick" water, the water took about 4 times longer to go through the filter than it does at our current home.

In our current home, our water is still very high in calcium.  Tea kettles, faucets, drinking glasses all show that, literally.  Flake son the bottom. I haven't seen any reason to be concerned.  We just have to wipe down the showerhead more, clean the teapot periodically, clean around the faucets, and put up with spots on glasses.

If your rainwater is acidic, like it can be in some regions, I think it's possible the roof water would get balanced out pH wise.  If it is used for watering plants, the ground will likely balance the pH, like others mentioned above.  If you use it for drinking and filter it, or boil it, the excess calcium will probably come out.

You could also test the pH of what comes off your roof, too, if you are concerned.  But if it doesn't feel like soap, it probably isn't too alkaline.

All in all, my husband and I feel so much healthier here than in Oregon.  There are a few reasons for this, but I do suspect the alkaline water here has something to do with it.  I had kidney problems in Oregon which have resolved, too.  So I don't think this water leads to kidney issues, from my experience.
 
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