Hey guys, I'm doing my first hardwood install using 3 1/4" wide solid maple Somerset prefinished flooring. Substrate is 3/4" plywood.

The installation guidelines say, "Allow 3/4 inch expansion space between the wood flooring and any walls or other obstructions."

I measured the existing trim and it is 5/8" thick at the bottom, so there would be a gap if I allowed 3/4" inch expansion. Will my floor spontaneously explode if I cheat it to 1/2" gap (giving me 1/8" wiggle room)?

I don't think adding a baseshoe is an option due to the style of the bottom of the baseboard (see pics)

Thanks for your help!
-Jeff

Pull your trim off and cut your sheetrock out an inch up from the subfloor.
That should give you another 1/2 inch of expansion and then there would be no need for base shoe.

I had the same situation....needed a 3/4" expansion gap and had 1/2" baseboard. I did as missouri recommended. I cut the sheetrock with an oscillating multi tool. Another benefit to doing this was that I could measure the layout line from the bottom wall stud plate instead of the sheetrock which may or may not have been straight.
If you don't have a multi tool and don't want to spend a lot to buy one get the Harbor Freight cheapo for under $20. The Harbor Freight blades are pretty lousy but will be fine for cutting the sheetrock.

It really depends on the width of the room. In a smaller space a 1/2" expansion should be fine for a nailed application. However if a problem ever arises be assured the manufacturer will balk at standing behind it. Cutting the drywall, thicker base, or adding the baseshoe resolves the problem.

the reality is you dont need this mjuch expansion space. 1/4" will be sufficient.

Do you really expect your floor to grow 11/2" inches?especially in normal residential settings?
it absolutely will NOT.

that same 1/4" expansion will be there in 20 years.

the 3/4 rule is for one thing only..if the floor were to ever taker on excessive moisture or direct water,this distance will allow enough room for the fasteners to completely withdraw and let go, subsequently and theoretically causing no harm to walls/cabinet etc..

this theory although not total BS is highly unlikely and 99.9% of your floors will just push themselves up and not damage any adjacent walls.

if your floor were to move 3/4" and actually 11/2 when you add both sides O will be the first to tell you your floor needs to be repaired/replaced./It will NEVER recover from that type of movement

I completely agree. You go into and home 50-100 wears old and the hardwood is right to the baseboards and even scribed the door casings. I generally remove the baseboard moldings, leave 1/4 inch and reinstall the moldings. in around 20 years have never had 1 problem with expansion.

It's probably just a case of being prepared for a 'worst case' scenario. The odds of the 'worst case' happening are probably nil but if you don't prepare for it now you wouldn't be able to go back and prepare later. Cutting the sheetrock is quick and easy....the multi tool goes through it like a hot knife through butter...put a piece of scrap flooring on the subfloor against the wall and rest the multi tool blade on it and just slide your way along the wall.

Thanks for all the tips!

I just picked up a cheapie Rockwell Sonicrafter oscillating tool for $49 and took up the sheetrock in one room (of 5) to allow for a larger expansion gap. It took me about 3 hours and made a hell of a mess. Seems the sheetrock installers decided to nail the sheetrock exactly where I needed to make my cutline, so every 16 inches I had to work around a nailhead, and come back to it with a putty knife to chip away at the sheetrock (and then pound the nail in with a nail set). So it wasn't exactly a quick fix.

If i do it in each room, that's probably 15 hours total of work just to take up the sheetrock, so not sure I'm going to do it in the other rooms. It would be different if I didn't have a day job, or if I had a crew.

Interesting discussion about the expansion gap. I had kind of been wondering how that whole expansion gap thing will work out when I do the stairs, where the flooring needs to come up snug against the step rise, as well as the trim stringers on each side.

Man my knees are sore!

3 hours for one room? How big is the room?
When you do the sheetrock you should only need to do the walls parallel to the flooring. Did your installation instructions say to leave a gap at the ends too? Floor boards expand across their width. Length expansion is negligible to non-existent.
Get some knee pads or rip some small pieces of the carpet that you've pulled up. Also, when you're doing the sheetrock hold the multi tool in one hand and a shop vacumn hose in the other hand. Just cut above the nail when you get to it, your baseboard should cover it. You only have to cut the sheetrock the height of your new floor board thickness so it could expand under it.
The stair treads will fit tight between the side skirt boards if the skirt boards are already installed. If you install the stairs from the bottom up the risers will cover the the back edge of the stair treads so you could leave a gap there.....same with the flooring that abutts the stairs....leave expansion gap and cover gap with riser.
Even if a stair tread is tight to the stringer or riser it can expand in the direction of its nosing.

It's just a little 10x13 room.

Thanks for the tip - nowhere I've ever seen in my many hours of online and print research has indicated that expansion only occurs significantly along the width of the hardwood and not the length. Makes total sense though.

The instructions just say to leave a 3/4" expansion space between the wood flooring and any walls or obstructions. It's a little vague, I might interpret this as 3/8" on one side of the room, and 3/8" on the other side, since that's 3/4" total. Or I might interpret this as a 3/4" gap on all four sides of the flooring (which I have).

As for the stair tread question, I think I'll start a separate topic so it doesn't get buried under this post. Thanks again for the tips! Very helpful.

I just looked up Somerset's installation guidelines which reference NWFA guidelines quite a bit. From what I have read and been told NWFA calls for 3/4" expansion gap on all sides.....some feel that this is excessive for the ends of rows and should be revised. I spoke to an employee at the company that I bought my flooring from and even though the instructions said that no expansion gap was necessary at the end of rows the employee said that he had been taught to leave an expansion gap at the end of the rows and would always do so. Maybe it was just easier and automatic to leave 3/4" everywhere.....old habits die hard. There are tables that will tell you how much each wood species will expand due to a change in moisture content. Just out of curiosity I'd be interested in what a Somerset customer service tech would have to say. One of my references says that a 20 foot piece of 3/4" solid hardwood is only able to change 1/4" along its length. Other types of flooring expand differently than solid flooring.