OK, I don’t know your particular tile so I cannot say if they need, or would have benefitted from sealing prior to grouting. It does not sound like there are actual grout stains on your tiles. I am thinking it has more to do with the spray sealer.

I am not a fan of spray sealers, they are a flawed concept in my opinnion – and I used to sell one! let me explain, the idea of a sealer that you can spray, and one that can be applied so soon (many state within 20 minutes to 2 hours of grouting) cannot be applying anywhere near the same amount or quality of sealer as doing it with a conventional sealer, after the grout has cured. They are designed to provide ‘some’ degree of sealing but more importantly they are designed to allow the tiler to seal the same day as grouting – so he can ‘add some value’ to the job, but also, leave the customer with a bit of protection, until he/she can get a proper sealer on the grout, once the grout has had time to cure.

They are also designed for speed and ease of application, ‘no need to wipe away residue’ (well, if they were applying a reasonable amount of sealer, there would be lots of residue or surplus sealer to remove). So the idea is the sealer is sprayed onto the joint, and because there is actually so little sealer there, the little bit that gets on the tile is supposedly so small that it won’t cause an issue. However, in prcatice they are over applied and there WILL BE some dried albeit barely visible, residue on the tiles. It is my guess that this residue is dull, colourless and not that noticeable on its own, but it will attract dirt and over a very short period of time this builds up and produces a dirty appearance.

I would hope that this is what you have, rather than a tile that is staied as that is harder to resolve. I would first try a product called microscrub (see all for stone ad on the blog), pre wet the floor, add a little microscrub and scrub the surface with a nylon brush or pad. If this does not do anything, try a solvent stripper, (you could try a little acetone or clear nail varnish remover – if that works, a solvent stripper should)

Hope this helps

Ian

First of all, we see far fewer issues with ‘matt’ finish porcelain than we do polished.That being said, there can be issues. Some can look and feel matt, but very smooth to the touch, however, under a microscope, they may have a fine, microspoic texture. This can be an issue if the texture is pronounced in that it can help to trap fine dirt particles. The only answer to this type of issue is to have to use something like a scrubbing brush occasionally to help clean the floor. There is not real way of checking this, as the shop selling the tiles is not guranteed to know the answer, usually you only find this out in use. One way to check is to buy/borrow a sample and tread on it with dirty shoes, bare feet, stocking feet, rub your hands over it, rub dirt on it etc – and see if any gets trapped or if it wipes clean really easily. If you have this issue, sealing will not really do anything to help.

Occasionally you can get a matt porcelain with a slightly porous surface – that can stain if strong liquid contaminants are left on it (red wine, beetroot, tea/coffee etc.) Sealing with a good impregnating sealer may help here.

So, you can check it is a good quality tile, by asking “is it from a trusted factory that you know?” for example, and just by doing the tests above, you can ask to see the tech data (water absorption figures for example – they should be <0.5).

With regard to under floor heating, there is not much to worry about, pretty much all the major brands are fine. there are no maintenance issues really. there are different systems: loose wires, wires in netting and newer, thinner foils and ribbon types that take up less room (thickness)

Main things to remember are that you should use insulating boards beneath to improve the efficiency and don’t spend money heating up the concrete, make sure you have sufficient space for the insulation boards, the heating mat/system and the tiles and adhesive.

Many tilers will tile straight over the mat, I do not recommend this, I always prefer to see a levelling compound used over the mat/heating system first, and allowed to cure as it means the tiler is less likely to damage the matt and also it makes the tiling job much easier.

Apart from that make sure you get the right capacity for the area you are doing, that you have a qualified electrician to actually install the electics (the thermostat and connecting it up to the mains) anyone can physically install the mat in place, but you must have a qualified sparky to connect it up, and many/most require their own RCD/RCCD and or fuse (not my field) – don’t let an unqualified tiler/builder/plumber/DIY enthusiast install the electrics.

Laslty, make sure the system is installed and the levelling compound cured and set, then TEST the matt – an electrician can do this for you. it is much easier to rectify/repair faults BEFORE you start tiling.

Hope this helps

Ian.