Hello,

i’ve been prepping my subfloor for LVP the past few weeks. trying to do everything right. the original floor is 1/2 inch plywood subfloor and a 5/8 inch plywood underlayment over that. the underlayment was a mess so i bit the bullet and replaced it all. im in the process of sanding high spots in my subfloor and laying back down new 5/8 inch underlayment grade plywood to match the original height. following all APA recommendations, i used screws to attach the new underlayment. im sanding high spots as i go and all the joint seams. some areas have split wood from the screws so im sanding as smooth as possible. i have some joint seams i want to fill and sand smooth, as well as some deeper screw holes from countersinking.

im in a dillemma on what is the proper material to use to fill joints, gaps and screw holes.

for the butt jojnts and seams where panels meet. most have a 1/32 gap or a little more as per APA recommendations. since screws are close to these joints, some split. im afraid to use henry feather finish in the joints as it says it isnt flexible. wouldnit still be ok to use?

there is also DAP flexible floor patch and leveler. its latex based but a little hard to use and very hard to sand.

should i fill all the edges and joknts with DAP flexible floor patch, and then the inner plywood areas with low spots/screw holes with henry feather finish?

im just afraid of crumbling/movement over time and somehow the feather finish breaks apart in moving joints or if there is any deflection in the subfloor it will cause the underlayment to move.

any ideas? i can also use wood filler on the nail holes, feather finish in the dips, and DAP flexible on the joints?