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TOPIC: Roofing over existing roof

Installing Metal Roofing over a Hardy Shake roof

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I live in Dallas, TX and want to replacemy Hardy roof with a metal roof. Some contractors say it is best to roof over the Hardy shakes and others say remove the existing roof. What are the advantages and disadvantages of doing either?
Bob Oldenburg

7/19/2003
I have seen numerous metal roof installations over the failed Masonite Woodruff product and have not seen any problems. This product was a little similar to Hardishake. Hardishake was part of a class action suit I believe. Check into whether you might have some money coming to help with the replacement cost. I do not know 100% how the old Hardishake will behave in the future if you go over it. However, protecting it from the elements with a metal roof should diminish or stop its deterioration. The new metal roof will be fastened to lumber beneath the old Hardishake. Keeping the old stuff in place helps reduce cost and mess (and landfill disposal) and will ultimately help the energy efficiency of your home. Provided your Hardishake is not too badly mis-shapen to allow the new roof to be installed over it, this is probably a good option. Todd Miller
Todd Miller
Isaiah Industries, Inc.

7/20/2003
There is no plywood under my hearty shakes, they are nailed directly to the spacer boards. Do I get adequate Maury protectio without the plywood base?
Guest User

7/21/2003
Sorry, Bob. I was thinking that Hardishake was usually installed over solid decking. Check with your roofing manufacturer and installer to see if the product and installation method being used will allow for fastening through the old roofing and into the lumber below at least a majority of the time. Todd Miller
Todd Miller
Isaiah Industries, Inc.

7/21/2003
I am looking for someone that has experience in reroofing a geodesic dome that has fiberglass shake panels.Do you know of anyone that could do this job? Thank You, Robert Fountain
Guest User

10/8/2003
Todd has more experience than I do and I believe we helped somebody last year. There are a number of metal systems than can fit however most are custom made to fit. Heat lost and the resulting condensationa are typical issues to deal with in this type of assembly. Use a good reioforced underlayment that breathes and tape it at penetrations. Also consider a vented mesh screen similat to that used under wood shingles on plywood that will help drain condensation. Try contacting ATAS a fellow member manufacturer, they have a couple of panels and make custom trims.
Allan Reid
Dura-Loc Roofing Systems, Inc.

10/9/2003