Great forum.

I'll be installing 3/4" 3" or 4" width BR-111 solid, (good choice?) most likey something like BC over AdvanTech subflooring in a 3 yr-old townhouse. I have a gas fireplace in the corner of the room at a 45 degree angle with a black marble hearth. I've never installed hardwood, but I'm very handy with other flooring and DIY in general.

I have pored many entries in this and other forums to get the consensus on whether I need an expansion gap between the frame and the hearth, but most replies tend to address a tile hearth and suggest a gap equal in width to a grout line filled with grout-colored caulk. (I will mitre the corners and either biscuit/glue join or route the boards to join T&G. Thoughts?)

However, a local hardwood dealer says it's ok to butt the frame against the hearth, and pictures I've seen in various forums do this as well. I've also seen such installations firsthand. Note that because the fireplace sits at a 45 degree angle, the field would be end cut at a 45 degree angle against the frame (if that matters).

I really don't think an expansion gap filled with black caulk would look nice, and I'd like to avoid a threshold if at all possble as well. However, either of those solutions looks nicer than a buckled floor, so I'm asking for expert opinion! I have the time, desire, and skill to do this job right, I just need some advice. I live in Northern VA, and RH is generally stable right now at around 50%.

Thanks!

If your home is climate controlled and your floor never gets hit with excessive moisture, you wont have a problem at all. To put it bluntly, if your floor gained moisture or got hit with water, you would have cupping problems and such. That grout line, siliconed expansion gap wouldnt do anything for you.
Picture frame the hearth with wood, or herring bone the corners.

Good luck

I agree. Expansion gaps are over-rated. Not really needed in a climate controlled environment. With today's fastening systems, excessive moisture absorption results in warped/cupped floors. They rarely even move toward the expansion space. If the floor wants to move or cup, that little 1/4" caulked joint isn't going to matter. But I will tell you, if you file a claim for failure, the inspector will note that and it could be a reason to deny any claim.

I wonder what would happen if the building experienced a power failure for two or three days.
Follow the installation guidlines and leave the space needed to accomodate building and material movement,,,, but if you can read the future...

Totally agree!

Yet to see lack of expansion, be the cause of the problem. Moisture is the over riding factor. Every buckled floor I have seen, and I have seen a lot of them, the expansion space is still there, and it has exploded out in the field, at it's weakest link.

I think some of these guidelines were written back when floors were nailed down by hand and shellac and wax were finishing systems. Todays nailers hold the floors "in place" better than the older hand nailed floors, which did allow for that lateral movement. And the finishes today are way more impermeable to moisture than the old shellac and wax. So, those very old floors MAY have been able to move sideways, but today's floors just cup and buckle when subjected to excessive moisture.

For what it's worth... I totally agree on this.

If the Installation Community insists on dis-regarding Industry Standards and Manufacturer Requirements, then please use wisdom in this decision.

It is true that wood shrinks and swells "In Place" and the only boards affecting the expansion gapping are the three or four boards located at the perimeter of the rooms.

Suggestions when installing without expansion gapping:

1. Install the wood at the maximum size.
- Install at highest Wood Moisture Content during summer.
- Installing at minimum size during winter is
2. Leave gapping of 1/32", the width of normal gapping. Not tight against a fixed object.
3. When Possible: Maybe leave 1/64" gapping between the boards (the last two or three) at the perimeter of the room to allow for swelling in areas of net fit.
4. Tongue side swells more than groove side. Maybe keep tongue side of board with a bit of a gap?