[Cob] Roofing question & thoughts

[Shannon Dealy]

On Wed, 14 Nov 2007, drub wrote:

> Am thinking of the roof design.  Have seen pictures of several cob
> houses with fairly flat roofs.  Gotta believe a membrane was used.  Some
> have been planted.
>
>    * What kind of membrane was used?  Conventional roofing membrane?
>      Some sort of swimming pool product?
>    * Is a membrane a good, long term choice?  As materials become more
>      expensive and less available, will this sort of membrane be
>      serviceable in future years of depletion?

For roofs that have been planted (living roofs), pond liner is probably 
the most commonly used membrane, there are a variety of different pond 
liner materials available, however, the most durable I have seen is EPDM, 
it's extremely tough, non-toxic, and has been around since at least the 
1940's.  From what I have read EPDM has a 50 year life expectancy, though 
that is probably only for exposed surfaces, if you keep it covered, it 
will probably last alot longer.  I have been using 45 mil (1 mil = 1/1000 
inch) EPDM for my roofs.  Best place I have seen for it is Water Garden 
Creations:

    http://www.watergardencreations.com/

NOTE: last time I bought from them, their prices included shipping within 
the continental USA, where shipping is extra with the other companies I 
have looked at.

>    * Would a conventional asphalt shingle be a better, more sustainable
>      choice?  It would likely be more available.  True?

Asphalt shingles are not that durable over the long haul and in particular 
don't hold up well to higher temperatures (most people I met while 
teaching in Australia had never seen it other than on TV and often 
weren't sure what it was).

>    * What other materials should be considered?  Tiles?

Tiles can be a good roofing system, however, they tend to be expensive 
and somewhat brittle.  Tile also makes for a very heavy roof so you need a 
roof structure comparable to what you would need for a lighter weight 
living roof.


Shannon C. Dealy      |               DeaTech Research Inc.
dealy at deatech.com     |          - Custom Software Development -
                       |    Embedded Systems, Real-time, Device Drivers
Phone: (800) 467-5820 | Networking, Scientific & Engineering Applications
    or: (541) 929-4089 |                  www.deatech.com