Installation Details · FAQ

Is shingle overlay legal in Illinois?

It’s legal in most Illinois municipalities up to two total layers. Madison County permits two-layer overlays; some surrounding counties cap at one (which means you must tear off before installing). But legal isn’t the same as recommended. Trill recommends tear-off in 95% of replacements.

The problem with overlay is invisible to the homeowner: you can’t inspect the decking, you can’t replace failed underlayment, you can’t reset the flashings, and the extra layer adds 200+ pounds per square to the load. Plus the new shingles telegraph the bumps and lumps of the old layer beneath, shortening their effective life by 30 to 40%. The cost saving is real ($1,500 to $3,000 on a typical job) but the long-term math usually loses.