A lightweight insulating concrete (LWIC) system was used to construct the roof of the Avalon Hayes Valley apartments in San Francisco. The LWIC provided a positive slope around multiple mechanical units on top of the building which was built with wood-frame construction over a podium slab.

Cell-Crete Corp. has been installing LWIC systems since 1970. The system includes low-density concrete, which helps create a positive slope and required R-values protected for the life of the roof. Cell-Crete worked on two of the five-story apartment buildings. The crew completed one roof per week.

Cell-Crete sales representative Ephraim Wilson says the LWIC system was the best option for this project, since other roof-deck systems tend to be too expensive and not very eco-friendly.

“If you used built up crickets, you’d have to sit there and manufacture a lot of things onsite,” says Wilson. “If they decided to use a tapered polyisocyanurate system, instead of the LWIC system, then labor costs would have gone through the roof.”

Cell-Crete installed 420 cubic yards of concrete to complete the 37,130-square-foot roof deck. The project was finished ahead of schedule and under budget in 2014.After installing the LWIC system, a layer of leak detection material and a single-ply roof membrane was attached to the top of the system. A pedestal paver system will be used as a walking surface. A recreation patio featuring an outdoor bar, lounge chairs, barbecue grills, televisions, and natural gas line fed patio heaters were installed on the roof for building residents.

Cell-Crete also worked on floors two through five. The contractor used an acoustical underlayment in all of the hard-finished floors. Next, was placing a gypsum-based underlayment in all of the interior locations with plywood subfloors. On the exterior unit decks, Cell-Crete installed standard light weight concrete as a finished deck surface.

“We’ve done a couple of projects like this since then. We are starting to see a serious uptick in demand for projects using the LWIC system,” says Wilson.