[Greenbuilding] Roofs

[Clarke Olsen]

     Putting shingles over existing is sub-optimal: the old ones should  
come off.
     That reminds us of another reason to like metal: it's much easier  
to recycle
     than tons of asphalt.
     Clarke Olsen

On Feb 1, 2007, at 9:52 AM, Lawrence Lile wrote:

>
>> Couldn't you do it right over the
> shingles (in case it rained during the construction and to save time)?
>
> You can only put so much weight over the roof.  With asphalt shingles,  
> I
> think the rule is 3 roofs is all you get.  When I reroofed my house
> there were four layers so some people cheat on this, but your building
> inspector won't be pleased with this tactic.
>
>
>>    What would the cost be to get someone to do this--compared to
> removing and replacing the shingles.
>
> Removing the old shingles takes a lot of elbow grease but is
> surprisingly cheap. It's a day's work for a crew of five on most  
> average
> houses. The right way to do it is to remove the old shingles, you could
> get away with leaving them on if there is only a layer. I wouldn't add
> foam and purlins and so forth over an old roof, this is just shoddy
> practice.  Yeah, if it looks like rain you need tarps, no way around  
> it.
>
>
>
>> Unfortunately, it's not a simple
> roof. I imagine the price of the material has gone up a lot. Hasn't
> steel gone up, like 700% in the last ten years?
>
> When I did my roof last summer, "barn metal" style roof with the screws
> was a little more expensive than asphalt, architectural standing seam
> (no screws penetrating the face, lasts a lifetime) was two or two and a
> half times as expensive as asphalt.  A pro can put the metal onto any
> shape roof.  I went with the standing seam, so I won't be up there when
> I'm past 70 trying to patch up a 20 year old leaking roof.
>
>
>>   Also, i'm in minnesota, not arizona, so another option could be to
> insulate (foam sheeting) on top of the existing roof and put the
> purlins and steel on top of that. My attic is finished, so I can't
> insulate it any better without demo-ing the ceiling.
>
>
> Minnesota, eh?  Yes adding foam sheathing on top of your roof, after  
> you
> tear off the shingles, and after you replace any rotten plywood that is
> under there, is an option, but it is unconventional and you'll be told
> by a contractor "It can't be done".  Keep looking until you find  
> someone
> creative.  Unless you add purlins you won't be able to do more than  
> 1.5"
> of foam in this way, the screws get too long to be practical.  I'd  
> think
> the purlins would be stronger and more wind resistant.
>
> Make sure you include snow guards like these
>
> http://www.alpinesnowguards.com/standing-seam-snowguards.html
>
> it is really scary when a big chunk of ice comes skiing off the roof.
> You'll need snow guards wherever people can walk, to protect mechanical
> equipment, overhead wires and landscaping.  Don't use the glue-on type
> that can pop off, use the kind that clamps a tube like a little fence.
>
>
> --Lawrence Lile
>
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