Frank from Oshawa Ontario has problems with cleaning mould off the grout in the bathroom and dirt off the grout in the foyer.
Soaked in dirt and stain in the foyer could be bleached out. If that doesn't work you will have to use a grout knife to remove some and re-grout. Remember to always dig down as deep as the grout is wide, otherwise new grout will not stick. Once it is clean, or new, make sure you get a good silicone sealer on the grout. Later, when it begins to look like dirty water is soaking into the grout, rather than sitting on top of the grout, it is time to renew the silicone protection.
For the mould in the bathroom, remember this is not dirt but a living organism. Start by using straight bleach and a tooth brush. If the mould is just on the surface, that will take it off and kill the spores. If that does not remove it, it means that it has sent roots down into the silicone, or between the silicone and the tile. Then you will have to remove the caulking and start over. There are only two silicone caulking removers on the market. One you put on a full bead of caulking and it causes it to swell up and pop off, most of the time. The other you have to cut away most of the silicone and the remover then takes off the film that is left. Neither work all the time, but you do need to remove all the silicone before trying to apply new silicone. Then use a bathtub caulk with fungicides, let the shower dry out between uses and keep the corners clear of bottles (which trap water in the corners). If you do get new mould and catch it in the early stages, you can control it with bleach.