QUESTION

An architect has inquired what the best water resistant barrier or vapor barrier product is used for external tile installation. They will follow TCNA method W244E, but just want some recommendations on what WRB works best for a commercial building exterior.

By the way, the building is in Boston.

ANSWER

ANSWER  - W244E can be a ceramic or glass tile or a stone application for an exterior framed wall with cement backer board over it.   If it is a cementitious backer board then they would put up sheathing over the studs (per building code) and then per ANSI A108.02 -3.8 Membrane or cleavage membrane section put a 15 lb roofing paper per ASTM D226 or reinforced asphalt paper duplex type per ASTM C171.  If you go over plywood sheathing then you need a Grade D membrane. A DuPont Tyvek product is often used as the building wrap.   If the backer board is a foam or  Coated Glass Mat board like DensShield then you don’t put the paper wrap on behind it.

We also always apply a secondary waterproof/crack isolation membrane over the cementitious backer board for moisture protection, to help prevent efflorescence staining, and as a crack isolation membrane.  Laticrete Hydro Ban is a popular liquid applied membrane.  If you use their entire single course system you can get a 15 year labor and material warranty.  Other manufacturers like Mapei and Customer Building Products offer similar products and warranties.

We do offer our consulting services to the specifiers and owners of projects.  We can write or review architecture specifications and provide recommendations and we can provide installation guidelines, quality assurance testing, and on-site quality control services.  We do have an inspector in the Boston area.  So you might refer our services to your client.