[RE-wrenches] Flashing vs Sealant... again

[Ray Walters]

We use a stainless fender washer between the lag and L foot both to 
prevent a galvanic reaction between the aluminum and zinc plating, and 
to seal over the slot in the L foot.  It also increases the strength to 
prevent the lag from tearing through the L foot in a heavy wind load.  
When we tighten it down, we always make sure that we have sealant coming 
out on all sides of the L foot, and the washer.  We've also used lags 
with rubber sealing washers too.

R.Ray Walters
CTO, Solarray, Inc
Nabcep Certified PV Installer,
Licensed Master Electrician
Solar Design Engineer
303 505-8760

On 4/16/2014 9:52 AM, don at energysolarnow.com wrote:
> As Ray Walters wrote, L feet installed with the correct sealant have 
> lasted as long as the comp roofs they're
> on.
> As can be seen in the attached pictures of L-feet on a roof that I 
> will soon be repairing, the wrong sealant eventually shrinks and 
> separates from the L-foot. Also the slotted hole where the lag 
> penetrates is exposed.  That's why flashings are used-- to cover up 
> sealant that won't last.
> Thanks for all the pointers to better sealants.
>
> Don Barch
> Energy Solar
>
> Ray Walters <ray at solarray.com <mailto:ray at solarray.com>> wrote:
>
>     ....If I'm putting a 2 inch hole through a roof, then that
>     constitutes
>     a penetration, and using a flashing is usually a good idea. But when
>     I'm filling a 1/4" hole with a 5/16" lag, its really much closer to
>     being a roofing attachment than a penetration.
>     BTW, we're not just depending on some adhesive to stop the
>     moisture. An L foot is really a 1/4" thick aluminum flashing. It has
>     at least 4 sq in. of surface area held permanently in place by a
>     mechanical fastener that is applying a significant amount of downward
>     pressure.
>      ..... L feet installed
>     with the correct sealant have lasted as long as the comp roofs
>     they're
>     on, 30 + years.
>

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