Quick question: when nailing up molding (base and casing), *where* do you like to nail? Thinner edges, thicker edges? Closer to edge of molding? Closer to center of molding?

FYI: I'm using MDF, to be painted.

Thanks!

It is better to nail inside the thick part of the molding. If you nail on an outside edge, there is more of a possibility of splitting or cracking occurring. Sometimes, I will even drill a small pilot hole that is just a little bit smaller than the nail that I will be hammering in to prevent splitting, even when nailing into the thickest part. I would then use a nailset on the head of the finishing nail to make sure that the head of the nail is flush with the surface of the molding. Using a nailset isn't always necessary, but sometimes it is.

I nail on a flat portion of the thickest part of the trim, as long as it's centered enough to pull both sides evenly against the wall.

I always predrill using the same nail that I'm using as a fastener chucked into the drill.

Thanks,
Json

If you are using an air nailer... it does not matter where you nail... MDF will not split unless you are really close to the end or if its already been damaged somehow. You want to get your nails into wood (the door jam or stud) if possible. Use caulk to fill in the hole and paint over, you'll never see it. In the case of the base trim... there should be a sill plate at the very bottom of the wall (a 2 x 4 parallel to the floor, on the floor) behind the sheetrock to nail to.

I wouldn't suggest nailing to the shoe only, since often, it's nearly non existent. If you have a second layer of subfloor and anything other than linoleum, it can actually be lower than the floor. Even if you have 1" of your shoe higher than your finished floor, you're going to want to fasten the top of the base as well as the bottom or it may roll away from the wall at the top, so you'll be looking for the studs anyway :)

Thanks,
Json

OK, thanks guys!

I'm in the middle of the project, and I'm using most of your advice.

Now, as for the nail gun: I'm using 4d nails. Sound right? (Using MDF molding.) Also, the nails are sinking pretty deep. I keep reducing the PSI, but to little difference. Right now, I'm down to 70 PSI.

On base board you want to nail in the flat areas only, and keep the nails and 1 1/2 away from each other for the smaller base and further apart for 5 1/4 base.
You want to avoid putting the nails really close to each other for the simple reason it just doesn't hold as well

As for casing 6penny or 8penny nails for the outside edge, or 2 or 2 1/2 finish gun nails
For the inside edge, thinner side, use 3penny or 4 penny hand drive nails or brad nails for a nail gun 1 1/4.

Thanks a ton.

The molding is finished (except for window casing -- live to fight another day) and looks great.