This might seem ridiculous, but I have a question about hiding the expansion gap. If the manufacture recommends a 3/4" expansion gap for 3/4" solid wood, how are you supposed to use 3/4" quarter round to finish. Is there 1" quarter round? I checked lowes.com and homedepot.com and don't see anything. There is also base board installed. I have thought about undercutting this to reduce the gap that needs to be covered by quarter round. My thought is if I undercut the baseboard, I will leave a 1/2" expansion gap from base board to edge. When finished I would have a 1" expansion gap from gypsum to floor, 1/2" being covered by baseboard and the last 1/2" covered by quarter round. Is this a logical approach. What do the professionals do?

Also I'm not 100% sure how to finish at the base of carpeted stairs. Again if there is a 3/4" expansion that seems like a large gap for the carpet on the front of the stair to cover.

My last question is about expansion gaps in general. Mfg instructions say to install at a RH of 35-55%. In the middle of January my RH has been 30% with the furnace running. if I wait until the RH is between 35-55%, let the wood acclimate and install, what happens next winter when the RH drops to 30%. I would think the wood would shrink, and then my expansion gap would increase from 3/4" to something greater. So back to my first question, what is the best way to finish/cover the expansion gap so that there is no risk of a gap every showing up?

The flooring will be nailed on a 22/32" OSB subfloor.

Any help greatly appreciated.

Really, nothing! Did I inadvertently violate some forum rule?

3/4 expansion is overkill if that floor moves 3/4 you got more problems than some expansion space will ever solve. I normally leave all the space i can while still covering the expansion space. with 3/4 round it's 1/2 to 5/8 and that should be fine.
ON the stairs you need a stair nosing. If its the but ends going into the nose fit it tight and leave the expansion on the opposite wall. if its the long side you need to install the nose first and work back.
Expansion in general; this time of year it can be tricky. If you dont get the r/h up before the install then the opposite can happen in the spring/summer when the r/h goes up naturally. the floor can expand to the point it cups. So, many people have to decide if a few winter cracks are better than a cupped floor 1/2 the year. Ideally in a perfect world you control the environment of the house with hvac/humidifiers/dehumidifiers and keep the r/h constant year round. this will keep your floors from moving excessively. all wood floors move, acclimation and more importantly the understanding of acclimation is where most floors installations go wrong.

gp,

Remove the baseboard and install new base board with a shoe. Problem fixed.

Johannes.

+1 this is what I did..

Remove all the baseboard...3/4 from the wall

Replace baseboard and add shoe

And if you don't like shoe or quarter round undercut the sheetrock. It's way softer than wood.