Yes. The most destructive force that will shorten the life of a exterior deck is water. Even if you use a sealer, water will still penetrate the wood to some degree, the wood will swell, and the surface can buckle. Leave the small gaps to allow for swelling and quicker dry time and air flow.
If you are using treated pine you can nail them down with no gap. When they dry there will be enough of a gap.
Joist possibly ? A joist is the boards under the floor and above the ceiling that span the room or building. What the floor or ceiling is attached to.
The floor of a house that is off the ground is first built with a layer of boards that is at a 45 degree angle to the load centers. To the average person, this layer of boards looks like a floor. However, they are wider than the boards than are normally used to go on the floor. The floor that people walk on will be put on top of these boards. The boards used for the floor will be thinner.
Standard wood floor joist spacing is 16" on center.
Yes they are not that heavy. A typical treadmill weighs as much as a king-sized bed with matress and boxspring, or an average dresser with drawers. Putting a treadmill on the second floor is not dangerous in terms of weight. You should consider the height of the room, and that constant wear and tear on the floor-boards, floor-joists, or cross-beams may create a "noisy" zone in your floor.
The boards or other material of which a floor is made.
If you're installing hardwood floor boards over a strong 3/4 inch plywood sub-floor, then yes, you can install the hardwood floor parallel to the joists. If your sub-floor is weak, then you should fix the subfloor.
The floor boards contract when it gets cold. The noises you hear are the floor boards contracting.
Steam cleaners do not lift varnish or shrink polished floor boards. The whole idea of applying varnish to a floor is so that the floor will be protected from moisture or liquid being absorbed by the wood.
under the floor boards
about 3.50
In your house on your floor like tile or boards
i think about 3 floors. around 2.8m per floor