Replacing Cedar Shingles With Vinyl Siding

House Doctor | Gary Dymski

August 22, 2002

Q. We are considering putting vinyl siding on our home. Do we remove the cedar shingles before installing the vinyl siding or do we cover them?

- James Zubulake, Albertson

A. Surface preparation is a crucial part of vinyl siding installation. I can't think of a case where siding would be installed directly over cedar shingles. Vinyl siding must be installed over a flat surface, and to achieve this flat surface with a minimum of work, siding installers generally use a half-inch thick rigid foam board. These sheets are nailed over the existing siding. If, however, your old siding is aluminum or vinyl, then it must come down before the new vinyl can be installed. By the way, don't fall for the line about the foam board's providing a significant layer of insulation. It offers very little; its primary function is to provide a flat nailing surface.

Another way to get a flat surface without removing the cedar shingles is to nail furring strips over the shingles, but this procedure has become somewhat outdated because of the increased use of rigid foam boards.

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There are situations when cedar shingles should be removed, says Bob Kramer of Robert L. Kramer Contracting Co. in Stony Brook. "If the shingles are hand-split shingles, then I would remove them before covering the home with vinyl siding," Kramer says. "Put vinyl siding over hand-split shingles, and the siding will be as wavy as the ocean."

Hand-split shingles range between 1/2 and 3/4 inch thick; machine-finished cedar shingles usually are 1/4 or 3/8 inch thick. Hand-split shingles tend to have a very rough and uneven surface, and even when they are covered with rigid foam it's difficult to achieve a flat surface.

If the old shingles are removed, it's sure to make your siding job more expensive. Your contractor will have to add labor costs for removing the shingles and carting away the debris.

But removing old shingles allows you to use fiber-type insulation that is injected into wall cavities and it also lets you repair rotting wood framing or sheathing behind the shingles.