This is guidance on the problems you may meet with stone floors, how to repair them, and on-going care.
Typical problems are:
Lift the slabs. If you have damp problems and find that the slabs were laid on concrete, consider removing the concrete.
To re-lay the undamaged slabs, set them in a mixture of sand, lime, and a little cement. If you wish, point them with lime putty. The objective is always to allow the soil beneath to breath so that excess moisture can evaporate. If you use concrete and the DPC in the walls is ineffective, then damp will tend to rise up the walls.
You may be able to turn damaged slabs over if the old hidden surface is reasonably smooth.
Broken slabs can either be used at the edge, or laid leaving a gap for pointing, or else replaced.
To clean a stone floor, sweep it well to remove sandy dirt which will otherwise act as an abrasive.
Wash the floor with water and washing soda; use 30ml of soda for a bucket of water. Add detergent if the floor has been waxed. Use caustic soda (15ml for 4.5 litres of water) instead if the floor is very dirty or stained.
Scrub and then rinse thoroughly.
Most experts advise against using a sealant but some suggest that a polish made from beeswax and turpentine can be safe as long as you do not soak the stone. Use a polish made from 3:8 beeswax and turpentine (no oil). Gentle heating in a double boiler will help to dissolve the wax so it can penetrate rather than sit on the surface. Do not saturate the bricks - you don't want to seal them totally, and too much polish will collect dirt and may become slippery. Subsequent coats can be applied annually.