[Greenbuilding] Paint a tar roof?

[RT]

On Sun, 07 Jun 2015 15:03:09 -0400, Benjamin Pratt  
<benjamin.g.pratt at gmail.com> wrote:

> My garage has an almost flat black tar roof. It gets really hot in the  
> summer, but I need to work in there, I know I can buy a silver coating  
> and there is a >white coating (but it says it won't work where the water  
> puddles),  What about painting it? Would regular oil based or water  
> based paint work? I believe >I can get free paint at the recycling  
> center.

Ben;

I have nothing to offer regarding painting a tar roof but I'm wondering if  
you might consider beefing up the roof joists by turning them into  
parallel chord trusses (relatively easy to do) and putting a living green  
roof up there ?

If $$$ are an issue, perhaps you could speak to some foundation forming  
crews and ask them to save their cut-offs of the dimpled drainage membrane  
for you instead of tossing it into the dumpster ?

As for turning the joists into parallel chord trusses ...

It could be as simple as screwing some 1/2" OSB or plywood gussets  say  
12-16 inches wide by say 24" deep in pairs to the cheeks of the rafters at  
the 1/3 or 1/5 points of the joist span and then affixing a 2x4 to the  
bottoms of those gussets. This can easily be acheived by one person  
working alone.

You might want to have one of your pals from the enegineering faculty do a  
quick calc to see if 24" deep trusses will handle your specific loading  
situation but unless the joist spans are exceptional long (in which case  
the roof would already be sagging badly and be in dire need of beeifng up  
my *guess* is that it'd do the trick.

A living green roof would likely be magnitudes better at keeping temps in  
the garage cooler than any paint you could apply and it could be the last  
roofing job it'd ever need.


-- 
=== * ===
Rob Tom DT7-64
Kanata, Ontario, Canada
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