FRT plywood and carpet installation

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Author Message Ann Sobiech Munson, AIA CSI CCS New member Username: acsobiech Post Number: 1 Registered: 12-2014 Posted on Friday, January 23, 2015 - 02:37 pm:    Has anyone dealt with direct-glue carpet tile finish floor over fire-retardant-treated plywood subflooring? FRT manufacturers kiln dry after treatment; FRT chemical is water-based, no petroleum products. Mfr data suggests finishing and adhesives are sim to untreated wood. BUT CRI (2011 installation guide) says treated wood is not a suitable substrate for glue-down installation. Carpet mfr does not think any adhesive will work. We have explored: 1/4 plywood underlayment (combustible); mechanically fastened mesh with gypsum or pc underlayment (raises ff 1-1/2" which causes issue with railings); sanding sealer over FRT plywood (incompatible with carpet adhesive). Any other thoughts or experience with this? Jeffrey Wilson CSI CCS SCIP Senior Member Username: wilsonconsulting Post Number: 161 Registered: 03-2006 Posted on Friday, January 23, 2015 - 03:43 pm:    How about an overlay of 1/4" thick cementitious backer units or fiber-cement backer board? I assume you have considered & rejected obvious alternatives such as non-adhered carpet tile (free-lay) or broadloom over cushion. Jeff Wilson Wilson Consulting Inc Narberth PA anon (Unregistered Guest) Unregistered guest Posted on Friday, January 23, 2015 - 03:45 pm:    Jeffrey nailed it. Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1281 Registered: 03-2003 Posted on Friday, January 23, 2015 - 04:35 pm:    First question, why is the subflooring FRT? Second question will depend on the answer to the first question. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com George A. Everding, AIA, CSI, CCS, CCCA Senior Member Username: geverding Post Number: 782 Registered: 11-2004 Posted on Friday, January 23, 2015 - 05:19 pm:    By the way, congratulations to Ann Sobiech Munson. She is one of the winners of the 2015 AIA Young Architect Award. And welcome to 4specs discussions. http://www.architectmagazine.com/architects/the-2015-aia-young-architects-awards_o.aspx J. Peter Jordan Senior Member Username: jpjordan Post Number: 796 Registered: 05-2004 Posted on Saturday, January 24, 2015 - 06:53 pm:    According to your post, CRI installation guide prohibits installation over "treated plywood", but doesn't say what type of treatment. They may be talking about preservative treatment. Although the process is similar, the chemicals are very different. I would try adhering the carpet to a sample of the FRT plywood (18 to 24 inches square) and see if it works. Ann Sobiech Munson, AIA CSI CCS Junior Member Username: acsobiech Post Number: 2 Registered: 12-2014 Posted on Monday, January 26, 2015 - 09:45 am:    Thanks everyone. It is a tricky and highly unusual situation - too late to change the assembly. Specialized platform construction for a Div I athletic program within an existing space, so code interpretation plays a big role, but strictest interpretation is that we need non-combustible material. Ann Sobiech Munson, AIA CSI CCS Member Username: acsobiech Post Number: 3 Registered: 12-2014 Posted on Monday, January 26, 2015 - 09:49 am:    I checked with one fiber cement underlayment manufacturer - for a few hours we thought this was the answer, until the technical staff from that manufacturer told me you could not use their underlayment with adhered carpet. We are doing a test with the FRT plywood, the adhesive, and the carpet. Loose lay may be our best option, as long as we can install to restrict movement at all edges. Ann Sobiech Munson, AIA CSI CCS Intermediate Member Username: acsobiech Post Number: 4 Registered: 12-2014 Posted on Monday, January 26, 2015 - 09:50 am:    Thanks George! Ronald L. Geren, FCSI, AIA, CCS, CCCA, SCIP Senior Member Username: specman Post Number: 1282 Registered: 03-2003 Posted on Monday, January 26, 2015 - 10:05 am:    FRT wood is not a noncombustible material per the building code. It cannot pass the ASTM E 136 test per IBC Section 703.5. To be noncombustible, it must be metal joists and deck with concrete topping, or a cementitious- or gypsum-based underlayment. Or, the floor structure is cast-in-place or precast concrete. Ron Geren, FCSI, AIA, CCS, CCCA, SCIP www.specsandcodes.com Ann Sobiech Munson, AIA CSI CCS Advanced Member Username: acsobiech Post Number: 5 Registered: 12-2014 Posted on Monday, January 26, 2015 - 10:18 am:    We are allowed FRT wood but not untreated wood in this assembly. Again, highly unusual situation but modeled after a very similar in-place assembly at another location. By "noncombustible" I mean the material between the FRT flooring assembly and the finish floor (which seems to eliminate untreated plywood underlayment).