Venting Metal Roof Over Shingles

Metal roof over shingles condensation.

Venting metal roof over shingles.

3 install 1 4 purlins down over the shingles before installing the metal roof the third way to install a metal roof over shingles is by applying 1 4 purlins over the shingle roof. Metal roofs must be laid flat on a vapor barrier because steel will condensate if there s any air space underneath it. Cool outside air travels under the shingles to the vented ridge pulling out moisture and heat. One of the big reasons homeowners choose metal roofing is for the uninterrupted run of metal from the top of the roof to the gutter which reduces the risk of leaks.

A metal roof typically does not increase nor decrease the need for ventilation. We do need to mention though one very rare scenario we have seen just a couple of times over our 35 years. Doesn t provide the flattest surface for the metal roofing to be installed over each course of shingles is about a 1 8 higher than the course just below it. Ventilation that meets code requirements is adequate for any type of roofing material including metal.

If it s slightly windy keep the steel downwind from you so a gust of wind doesn t knock you over. Also don t go up on the roof if it s windy.