Renovating the bathroom and have 3/4" shiplap for subfloor.
Tried to glue and screw 1/4" plywood to "beef it up" a bit and it just bounced in between the joists(16" o.c.) so I pulled it up before the glue could dry as I didnt want to continue on with porcelain tile and have them cracking.
Should I skip trying to add another layer of subfloor and go with Schluter Ditra where the tiles will be laid and leave the shiplap under the bathtub?
Location: Beautiful City of Kingston, Ontario, Canada
Rewards Points: 75
Tiling over shiplap subfloor
I'm not sure what code is in your part of the world, but here it's 5/8th over 5/8th (or 1.25 inches) like Just Bill said. I'd suggest screwing down 5/8" plywood over shiplap as there is significantly more movement there than there would be in a plywood subfloor.
Don't just add another 1/4" sheet of plywood, two sheets of 1/4" inch aren't as stable as one sheet of 1/2".
Good luck and have fun, it should look great when you're done!