Exercise rooms in the garden fail on three things: the floor is too bouncy, the ceiling is too low, and the room is unbearable within twenty minutes because nothing moves the air. All three are decided before the building is ordered and none of them is fixed by the equipment you put in it.
The floor of a home gym in garden buildings carries more than you think
Dropped weights are an impact load, not a static one, and a lightweight joisted floor will drum and flex under them. A slab with a resilient sports layer over it is the usual answer for free weights; a suspended floor is fine for yoga, mats and bodyweight work. Decide which of the two the room is for before the base is poured, because the base is the one part nobody can change afterwards.
Height, and why a gym in the garden is so often too low
Permitted development limits the height of outbuildings, more tightly within two metres of a boundary, and manufacturers design to those limits. That leaves an internal height which is comfortable for a desk and marginal for an overhead press or an inverted yoga posture. If height matters, either move the building away from the boundary or lower the floor level, and confirm the internal clear height rather than the external one in writing.
Heat and air
A small insulated box with two people exercising in it gets hot quickly and humid immediately, and glass makes both worse. Cross ventilation with openings on two sides, a mechanical extract, or a small heat recovery unit are the options, and the overheating principles for habitable rooms apply just as well here. Condensation on the inside of the glass in winter is the visible sign that the ventilation was never designed.
If anyone else uses it
A garden room used only by your household is incidental to the house and normally stays within the outbuilding rules. Teaching classes in it, taking paying clients or having people arrive by car is a different use, and it can need planning permission, may attract business rates on that part of the property, and will certainly need its own insurance. Ask the question before the building arrives rather than after a neighbour asks it for you.
Questions people ask about garden yoga studio
Can a garden room floor take dropped weights?
Only if it was built for it. A slab with a resilient sports layer is the usual answer; a lightweight suspended floor will flex and drum.
Is there enough headroom for overhead lifts?
Often not, because outbuilding height limits constrain the whole building. Confirm the internal clear height before ordering.
Do I need ventilation in a garden gym?
Yes. Two people exercising raise the temperature and the humidity fast, and without designed ventilation the room becomes unusable and damp.
Can I teach classes in it?
That is a different use from incidental household use and may need planning permission, business rates and separate insurance.