Floor and wall board moisture content

[pbailey]

I did a search on the Internet for the average moisture contact of a home with central heat and air. The answers I got were typically 30 to 40%. My question is why dry wood to be used inside down to 10%? Would it only expand a little bit over time?

[JoshNZ]

Think you might be mixing terminology, relative humidity in your home and timber moisture content aren't the same number.

Relative humidity of 35% in a 70F home let's say, equates to an equilibrium MC of more like 7%.

[Southside]

The industry standard is to dry hardwood flooring to 7% MC. Even at 10-12% you will end up with movement, shrinkage, and a poor floor. 

[Don P]

Start here and holler back if it's clear as mud;
Equilibrium moisture content - Wikipedia

[trimguy]

What is the industry standard for SYP ?

[Ianab]

What is the industry standard for SYP ?

Construction pine is usually only dried down to below 19%. At that number it can't stain or rot. The wood you buy may be less if it's been stored for a while, and of course it dries out over time. Bit if it's wall stud for example, no one notices if it gets 1% narrower over time. 
But with floor boards or furniture, you notice the gaps or other random movement.
The 7% MC for "furniture" dry hardwoods is basically an average that works for most of the continental USA. Other areas, especially coastal, might have a higher EMC. It's more like 12% here.  

[Southside]

10% on SYP.  Below that and it gets brittle, splinters, and tears apart hard when milling.  

[Don P]

The "turn that truck around" point in Raleigh for cabinets, millwork and furniture which isn't too far from you was 13%. We could maintain 12 in the open shops but not much drier. With SYP when I left there more high temp kilned wood was coming in. Very slightly darker but the main thing was I could hear the difference at the whirlwind saw as I broke it down. I'm pretty sure the sound was an internal tension set from the very rapid drying.

[trimguy]

Sorry, I knew what I meant 😂. I was talking about pine for trim work, wall paneling, flooring, etc. Thank you.