Im replacing a 100 year old doug fir floor in a room 60x35 on a second floor. Its a very high traffic area so the client and I decided on brazillian cherry. The flooring has been aclimatizing for a month and will sit in the room for another 2 months. The job is in the Yukon, so as you can imagine we have a really large window of temp and humidity. The floor is mitered from the corners to a rectangle in the middle of the room. I plan to biscuit and glue the miters. I decided to use cleats for fasteners with 15lb felt underlay. The subfloor is 3/4 diagonal t&g. I plan to screw the subfloor into the floor joists once the fir is removed. For a finish we decided on pure tung oil with a yearly recoat maintainance program. Ive installed and finished a few floors with no problems. Im just really worried there may be something Ive missed. Any comments or concerns would be greatly appreciated.

I think I would spline those 45 degree mitres. And no glue, Im thinking there may be a fair bit of movement during the summer and you will want to allow that to happen.
Presumably, you have opened up the flooring bundles and spread the floor out to allow for equal acclimatizing.
That is a huge amount of interconnected flooring your dealing with, not to mention it grew up in a "slightly" different climate.

The bundles are stickered with 2x2 spacers. The manufacturer said there was no need to undo the bundles. I checked the moisture and the flooring was around 6 to 8% lst month. Just got back from holidays so will recheck it today. I will open a few bundles and check in the middle. Because of space limitations I will have to move the flooring a few times around before install. Its 9 thousand pounds of flooring so as you can imagine its a move when in bundles, so loose pieces would be a job. But that said I guess better to be safe. I would feel safer laying the floor standard. I figure it will move alot also and think the miters will be problematic considering the size of the room. Splines with no glue is a good idea. It would still allow for movement and the mitres wouldnt be springey.

So I went in and took some readings. YIKES. 2 to 4% on top of the bundles and 5 to 8% inside. The problem is the top pieces are bukling and warping, plus there is quite a bit of checking on the ends. Im worried that if I undo the bundles and spread out the material that everything will warp, buckle and check. I'm also worried that if everything dries out to 2 to 4% it will be too dry to lay and if I do the final product will end up lifting during a wet fall. It seems that 5 to 6% would be perfect to install for this climate. The humidity in the room is 20% now that its -20. Im sure it was around 10% at -45 during the last month. I'd rather a few planks open up than have the floor lift. I wonder how many picture frames I could make with all this.

First thing to do in this case is add some humidity to the space. This is crucial, you cannot allow an uncontrolled environment. Do you know the average humidity levels for your area during the summer? Is the space air-conditioned? You have to bring the winter climate in the room nearer to the conditions found in the summer. I will get back to you after giving this situation some thought.
Hopefully someone in this forum has some good ideas, you could (read:will) have a major problem with this installation if you dont resolve the humidity issues before you install the floor.

Yes, buy an inexpensive humidistat to measure and monitor your relative humidity. I got one for $18.00 at Walmart. Where you live, the freezing temps take all the humidity out of the air plus the heating systems further dry the air out. I'd bet you interior RH is about 10% right now. It is way too low. You need to get it up to at least 40%. This can be accomplished in several ways. By an actual humidifier; maybe two. Or, boil water on your stove top. A hassle. Raising the interior humidity will be more comfortable to live in as well. Fortunately, people and floors like the same levels, between 40 and 60 % relative humidity.

I have a humidistat in the room. Its at 20% right now at 20C or 70F. Outside temp of -15c. Like I said it MAY have dropped to about 10% last month at -50 but the winter average is probably about 20%. The building has a forced air boiler system with no in line humidity control. Unfortunately I dont think its an option to put one in so Im forced to deal with these conditions. In hind sight I maybe should have went with an engineered pre finished floating floor but the client didnt like the micro bevels. They wanted a sanded floor. The summers here are similar to Vancouver, only shorter, with an average humidity of about 35 to 40%. The room is 65 by 35ft. The floor is mitred to a rectangle in the middle. I'm planning on starting in the middle with the rectangle and working out. (What do you think). I'm hoping the tung oil finish will help keep the wood in check to a certain point. If I thin it 50% for the first coat it will really sink into the wood slowing down the seasonal expantion and contraction. I dont plan on troweling a filler coat as I expect the floor to maybe open slightly over time.

A floor finish, regardless of the type, can slow the transmission/absorbtion of moisture vapor but not completely prevent it. If this is a client's home, it is THEIR responsibility to maintain proper temp and humidity levels for the flooring to perform well. It is YOUR responsibility to inform them of this. If you install the flooring in a situation where it is very dry, then come the time of year where the RH is more normal, the flooring WILL swell and appear cupped. Then you'll get compression set as the force of the swelled boards push against each other causing the edges the be crushed and the boards to move ever so slightly. Come the dry time of year, the boards will shrink again, but now there will be gaps in between due to the compression set. To solve this, the client can buy some inexpensive portable humidifiers. They only may need one, depending on the size of the home and area of the floor. Their sinuses will be better off as well.

Thanks Gary. The building is a commercial space. I will talk to them about putting a humidifier in line with the heating system. As far as laying the floor down, does it make sense to start with the rectangle in the middle of the room and work out to the 4 corners? The floor is mitered from the corners to a rectangle in the middle.

When doing a floor that is "wrapped" with an apron ( border), it is often easier to lay the field first, trim off the excess, then install the apron/border. The downside? You have to work up to the walls instead of away from them, which is slower and either requires some face nailing or gluing the flooring down. But you save time in the field not having to net cut each board to a border. Remember though, with a T&G floor, you need to cut a slot around the perimeter of the field to insert a slip tongue. This way, you will be able to T&G the first coarse of the apron/border to the field.

Laying the floor out from the centre, especially in a large space like you are dealing with gives you one more advantage. Although wood expands in width if exposed to excess humidity, the actual direction of travel is primarily in the direction the tongue of the boards points to. In your case, instead of the travel being in one direction, it will be equally distributed towards the entire perimeter of the room. REMEMBER to allow sufficient tolerance at the walls and other obstructions to allow for this.
And as Gary says, you must connect the centre rectangle to the border with a groove and spline. By starting in the middle of the space, you only need to do this on the ends of the rectangle and in the centre of the rectangle. Or if you start along one edge of your centre area, a spline will be needed where you turn around to start your border. Make sense?

Makes perfect sense. If I undercut the drywall I will be able to leave 3/4 inch all around. The drywall is 1/2 and the base is 1/2. Do you think this will be enough considering the room size?

More than adequate. ANY floor ( except a large gym ) that would expand enough to fill that 1" gap would have a lot of other major issues, like, it was probably flooded.