Step-by-Step Install of a High-Performance Cathedral Ceiling

cathedral ceiling

When designing the roof assembly and cathedral ceilings for Model ReModel 2022's in-law suite addition, builders Nicole Tysvaer and Matt Kulp of Symbi Homes worked to prioritize energy efficiency, wellness, and beauty. 

"We needed a minimum R-49 roof, a ventilation system to prevent moisture problems, and increased ceiling height to create a sense of spaciousness in the main living area," says Symbi Homes CEO Nicole Tysvaer. 

Symbi chose sustainable, formaldehyde-free Greenfiber Sanctuary, a dense-packed cellulose insulation blown into the 18" cavity of their roof trusses (R-3.7 per inch), which exceeded their thermal protection goals, but also added considerable weight to the roof assembly. 

To prevent any future sagging of the material, Kulp added 3/4" battens across the cellulose netting and finished the ceiling with 1/2" birch plywood, which will be left exposed. 

"The clear-coated plywood ceiling is absolutely beautiful and gives the addition a cozy, modern cabin vibe," explains Tysvaer.

Here's an illustrated step-by-step explanation of the installation process:

(1) 24" DCI Products SmartBaffles covered the entire underside of the roof plywood to create a channel for natural ventilation, helping to reduce roof temps and prevent moisture buildup.

cathedral ceiling install

(2) After installing baffles, Symbi Homes sealed the seams and voids in a two-step process. First, polyurethane foam insulation was applied with a sprayer. Second, the crew returned the next day to complete the air sealing, attending to even the most minute gaps and cracks using cans of polyurethane insulating foam with a thin straw applicator.

ceiling insulation spray foam


(3) Southland Insulators installed netting to hold the Greenfiber Sanctuary dense-packed cellulose in place.

cellulose insulation install

(4) Kulp crisscrossed the roof trusses with 3/4" wood battens installed 16" on the center to prevent any protrusion of the insulation material.

cellulose blow in insulation


greenfiber insulation

(5) The cathedral ceilings were finished with exposed 4'x8' sheets of 1/2" birch plywood installed with a 1/16" gap for expansion. After filling screw holes with wood putty, the plywood was lightly sanded and coated with a clear water-based satin polyurethane sealer.

plywood ceiling


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