Waterproofing Canvas

[Yurts_latvia]

Hi all at the forum!


First post from us. We're making yurts in Latvia and investigating different options for a good waterproof roof.


We don't get too much rain here in Latvia - in winter it's mostly snow and in summer it's just the occasional (but heavy!) thundery downpour.



We want to keep the roof pitch as slight as possible to improve

heating

capacity during winter. Our first yurt frame is set at 25 degrees.


We want to use natural materials where possible, so cotton canvas is the obvious choice. If it is untreated, will a waterproofing treatment such as Nitwax Cottonproof be enough?

Would others be so kind as to share their experiences with roof materials, treatment and roof pitch to stay dry?




With many thanks!


Charlie

[Bob Rowlands]

If you are making your cover from scratch, buy 'Sunforger' treated canvas by the roll from any of a number of suppliers. The advantage is the professionals apply the waterproofer at the factory, instead of a messy home do job. Plus the canvas is rolled and nice and flat for sewing instead of a wadded up mess.

If you are buying the cover, buy it pretreated with waterproofer.

I would find it odd to not be able to buy a yurt cover with sunforger canvas. However if you can't get pretreated canvas for whatever reason, apply 'Canvak' or Nikwax' or other waterproofer with the cover on the yurt.

'DO NOT' use Thompsons water seal. That will be a fail. I know guys that did that to a perfectly good canvas wall tent and ruined it. Good luck.

[Yurtman]

I would recommend a treated canvas too. We use Sunforger. I’m not a fan of vinyl, but it has sone great qualities like completely waterproof and will last 10-15 years.
If you go the canvas route and want to do your own waterproofing, make sure you pre-shrink the canvas before you treat it.

[Bob Rowlands]

Thanks yurtman.

[Yurts_latvia]

Thanks so much both of you for very helpful advice!


We have two types of canvas - one untreated, and the other light green one from Russia, treated as waterproof - but not sure the details. I guess we'll find out and apply extra waterproofing if we need it.


How long would you expect Sunforger canvas to last if the yurt was up year-round?


Would increasing the roof pitch from 25 degrees to 30 make a big difference?


Thanks again!


Charlie

[Bob Rowlands]

My sunforger factory treated 17 ounce cotton canvas was grade A at water repellency the first year. B the second. C to D the third, F the fourth, and a total fail after that. That's year around, no cleaning, no reapplication of any waterproofer. I call that VERY good service for a natural material left outside in the elements year around, that does not off gas a strong smell.

Beats me about roof pitch and longevity. My guess is Sunforger and equivalent treatments in canvas are gonna absorb water regardless of pitch, as the repellent wears out in a couple three years.

As an aside here, I would not get canvas that is treated with a heavy opaque wax and dye. My son bought me a roll of 'olive green military' canvas. There's a much heavier dye and wax in that stuff relative to Sunforger. Water sheets off it like it does off a plastic tarp. My guess is it probably would keep the water out for a couple years longer than Sunforger. But by God it is absolutely awful stuff.

I made a small tarp out of it last summer and had it erected continuously for a few months while building my shed. Water poured off it immediately in a rain but it till stunk to high hell even after a few months of intense sun. 'No chance' I would live in a tent made with that stuff.

Good luck.

[Yurts_latvia]

Very useful info again, thanks Bob!

So maybe we should search for Sunforger. I found some 12oz at fabricuk.com , for around £7.20/m2

I guess this is a decent price, or should I shop around a bit more? Do you know any other recommended outlets? We're now based in Latvia, but shipping from the UK, or mainland Europe is cheap enough.

Cheers!

Charlie

[Bob Rowlands]

I haven't bought canvas since 2013. I'm not up to speed on price, alternatives to sunforger, flame treatment, or suppliers.

I believe I bought the tarp I made into my yurt cover from 'mytarp' online here in the U.S. I just can't remember. If I was making another canvas cover from scratch I would go online and call a few suppliers. And have a commercial sewing machine available.

Lastly, if I were doing another canvas cover, I would get a white tarp and make a second cover for the roof. That is a cheap way to keep the bulk of

moisture

out of the canvas, and the sun off it. Snug the plastic with the upper tension rope. Keep the cover long and roll it around the rope as you go up the wall. That should increase the canvas life. But, I got say it beats me how that would effect the canvas from

moisture

within the yurt. I haven't done it. Just an idea. Good luck.

[Yurts_latvia]

Hi all,


I wanted to get this thread going again because one year on and I'm still unclear about the best options for yurt covers - especially the roof.


The cotton canvas that I've gone for in my outdoor yurt does let tiny droplets of spray through the weave when it rains hard. It's not a disaster but I'm looking for better alternatives.


I was really put off of PVC covers by yurta.ca's commentary, listing all of it's possible toxic effects by off-gassing, and the lack of breathability of PVC.



Are some forms of PVC much safer than others?


I'm sure there has to be a better option than this for breathable, non-toxic covers,

yet in this thread, Bob's experience has told us even the best Sunforger cotton canvas only lasts for two years in good condition, with a maximum of 5 years lifespan.

Yurta.ca use a polyester/acrylic weave which is breathable and long lasting, which sounds great...


I also used to hear that hemp was the ultimate choice for durable, natural tarpaulins and tents, has anyone got experience with hemp?


Another idea of mine would be to use PVC just for the roof whilst the walls are much less likely to leak and could remain breathable cotton. Maybe this compromise would keep the space well ventilated, dry and hopefully free from mold.



Any suggestions or experience greatly appreciated,


Cheers



Charlie

[Jafo]

Most of the covers have a base to them that is not vinyl (polyester usually) and then there is a liner it sits on top. If there is any off-gassing, it happens outside, not inside. Even from the first day I put mine on, I could never smell anything from the roof.

The walls I use are the polyester which are light and durable and again, sit on top of a liner.