We want to build a small floating deck at the rear of the house. Should we put gravel under the deck since it will be right next to the foundation of the house? Should we place the gravel next to the foundation or so many inches away from it?
Gravel under the deck and touching the foundation is fine.
Before doing so , ensure the grade slopes away from the foundation for water drainage. Don't rely on the gravel to act as a slope , rather the soil needs to slope away , the gravel is merely covering the soil.
Personally i would also lay down landscape fabric down first then lay the gravel over top.