From our Fixit columnist, Karen Youso:

Piling new shingles on old was a way to save money in your re-roofing project. But a change in the state building code makes that practice a no-no in southern Minnesota.

The common practice of laying new shingles over existing shingles, up to three layers, is no longer allowed under Minnesota’s Building Codes and Standards. The state, designated a moderate to severe hail exposure state, now limits the number of shingle layers depending on where you live.

In most of the northern half of the state, only one layer of shingles can be covered with a new layer. In other words, roofs can carry no more than two layers of shingles.

In roughly the southern half of the state, including the metro area, new shingles cannot go over an existing layer of shingles at all. The shingles must be torn off and the roof cleared to bare wood with every installation.

Click here to learn what is allowed in your area, go to or contact your local building official.

But even when the practice of laying new over old was allowed, it wasn’t a good idea, according to Bill O’Meara, an instructor with Community Action, a non-profit organization in Hopkins. New shingles laid on old just don’t last as long as they do when installed on the roof deck, he said. And, in many cases, laying new over old will void the manufacturer’s warranty.