Yes and No. The residential building code allows for no more than 2 roofing layers to be installed on a residential home at any given time.
- Shingle roof on top of another shingle roof? Yes and No. If you have a basic “3-tab” shingle roof, you can install any other type of shingle roof on top of that, because the 3 tab gives you a flat base. If you have an architectural shingle, dimensional or premium, the contours create an unbalanced base to install new shingles. (link to composition roof)
- Shingle roof on top of a wood shake roof? No. The wood shakes will cause problems due to the expansion and contraction over time. The shingles will also have a wavy appearance due to the lack of a flat decking surface.
- Metal roof on top of composition shingle? Yes. Any metal roof with an air gap, like a metal shake roof, can be installed on top of any composition shingle. Technically, you can install any type of metal roof on top of composition shingles. However, we do not recommend installing sheet metal roofing or standing seam on top of composition, because any variance in the shingle installation, could affect the look of the flat panels.
- Metal roof on top of a wood shake roof? Yes and No. Metal Shake, Metal Shingle and Metal Tile roofs, which all have air-gaps, can be installed on wood shake. Sheet metal or standing seam roofing systems cannot, due to the need of a flat roofing deck.