We cleaned a few of these in our time..
Clean the sauna often to keep a fresh and well-maintained appearance. Maintenance Programme!
Use a bucket of warm water with a mild detergent soap and a clean sponge or rag to wipe the bench surfaces and floor.
You could use Bio-Shield Lemon from Clover Chemicals. Or your prefered cleaning agent that cuts through body fat..
Avoid heavy detergents, they could discolor your wood or leave a residue, which could emit irritating or harmful fumes.
You may clean the rocks after they have completely cooled. Soak them in a soapy (light detergent) mixture of warm water.
Wash them off with a sponge, then rinse in clean water. Allow them to dry then re-apply rocks to the heater trough. Clean the heater of the foreign substances. Gradually build heat in the sauna to totally dry the rocks.
Never ever turn a hose on the sauna to wash it down - thats what they advise. We did use a hose to wash them down but these were near swimming pools.
Also a good idea was to use a squeegee and mop - used for window cleaning to wipe down the walls.
Grout
ok this could be tricky and you will need to test the grout.
By testing I mean find out if it is soft or hard. If its hard then you could use an acidic cleaner. Failing that if it is soft then you may need to re-grout.
We use a soft but small wire brush and run up and down the grout. You have to be careful. Also you need to find out if there is mould if so you could find that almost impossible. Bleach is a good barrier for mould.
I hope this has been of some help
Dave