Stone, CMU, and Wood Window Sills

Wood window sills are common on historic buildings. In most modern construction, both in commercial and residential contraction, stone or CMU window sills are more common. CMU stands for Concrete Masonry Unit. In the photo collage below you can see the old rotted wood sills which were removed by a contractor and replaced with masonry sills.

The rotted sills shown above are not historic and likely only a few decades old, yet the sill have already rotted in a relatively short period of time. The CMU sills will resist the deteriorating effects of water and weather mush longer.