Rookery

[quote user="BIG MAC"] Remove old floor, tank screed with bitumastic paint, 40mm cellotex laid loose (Ie not screwed down, 18mm moisture resistant chipboard laid direct to cellotex (Good idea to have 5mm expansion gap round the edges and gun this is with low modulus silicone. Once sealant dry prime surface ready to receive a electric heating matrix (A LA Messrs Srewfix etc) making sure you don't put it where you are then going to drill or screw through! Run cabling out to desired locations for power and stats Apply ceramic tiles (Use wooden floor adhesive) and fasten skirtings or gun in joints in suitable sealant. Fit Sanitary ware. Make plumbing and electrical connections.  Toasty , cheap, tidy......will that do? [/quote]   So you're suggesting he fixes his ceramic tiles onto a heating mat onto a floating timber floor? The heating and cooling could cause more movement than the adhesive/grout can cope with.  http://www.netweber.co.uk/tile-fixing/weber-products/problem-solutions/internal-floor/tiling-onto-floating-floors.html http://www.netweber.co.uk/tile-fixing/weber-products/problem-solutions/internal-floor/tiling-with-under-floor-heating-or-under-tile-warming.html#tab0  http://www.netweber.co.uk/tile-fixing/weber-products/problem-solutions/internal-floor/tiling-with-under-floor-heating-or-under-tile-warming.html#tab1 I would do it thus: Prime slab. Fix insulation boards down with single part, cement based flexible adhesive. Lay heating mat or cables. Cover cables with latex levelling compound. Fix tiles with single part, cement based flexible adhesive. Finish with grout mixed with a grout admix. Make sure the initial warming up is done in accordance with the manufacturers recommendations.

As before, the information I give on the subject of wall and floor tiling is based on many years experience as a professional, trained tiler. Anyone doubting the information can check here http://www.tiles.org.uk/help/answer-weight.shtml here http://www.netweber.co.uk/tile-fixing/weber-products/problem-solutions/internal-floor/impervious-tiles-or-substrates.html#tab1 and here http://www.netweber.co.uk/tile-fixing/weber-products/problem-solutions/internal-walls/tiling-onto-plaster.html#tab1 Yes, many people will fix tiles in the manner of Big Mac and get away with it. It doesn't make it right though.

If tiling over existing tiles you first need to determine the extra weight you are adding. A gypsum plastered wall can take a total weight of 20kgs per sq mtr, plasterboard 32kgs. This is the total weight of the old tiles, adhesive and grout plus the new tiles, adhesive and grout. If the combined weight exceeds this, there is a risk of the lot pulling off the plaster. The existing tiles should be soundly fixed and cleaned. Sugar soap is good for this. The glaze on the existing tiles can be scored to provide a key but this is not absolutely necessary. The new tiles should be fixed with a polymer modified, cement based adhesive. This provides for a chemical bond between the new tiles and the existing glazed surface. Priming is not necessary. Weber make good adhesives as do Mapei. Check out their websites for more guidance. PVA should not be used when preparing for tiling. I know lots of people do but its still not the correct product. I've not fixed self-adhesive floor tiles but I cant see a need to prime the ply first, just make sure its dust free.

[quote user="BIG MAC"] [quote user="Rookery"]If you're going to fix tiles, on no account use pva on the plaster/plasterboard. Its completely the wrong thing to use.[/quote] If tiling to plasterboard then a weak solution of PVA is exactly the thing to use to give a good cure....nothing to do with waterproofing it slows the drying time for the adhesive and allows it to set up properly without drying out too quickly. (Ex bathroom fitter) [/quote] I must disagree and so will the vast majority of tile adhesive manufacturers as well as The Tile Association and probably BS5385. PVA sits on the surface, in the same way as wallpaper adhesive. When it gets wet, which it will with adhesive, it becomes 'live' again and could cause de-bonding of the tile, especially with heavy ones. If using a cement based tile adhesive on gypsum plaster or gypsum based boards, you should prime with an acrylic tilers primer. This serves 2 functions. Firstly, it stops the adverse chemical reaction you get between gypsum and cement (Ettringite) and secondly it stabilises the surface, preventing the plaster sucking out the moisture too quickly. If you are using a dispersion adhesive, generally speaking, they do not need priming first, unless the surface is overly dusty or porous. Whilst on the subject of tiling onto gypsum plaster, you should never tile onto a bonding coat, only a finish coat. (Professional tiler in the UK, not advertising and not looking for work, only offering professional advice )

Yes it would be if it was just dirt but from what the original poster said, the tiles have lost their sheen due to foot traffic. Thats unlikely to be just dirt requiring a clean. The surface will have been worn down and it sounds like it needs re-honing/polishing. In any event, terrazzo are porous and any ingrained dirt or stains will be difficult to remove with just a cleaner.

No it isn't. I'm sure a bit of t'interweb research would reveal the firms that do this kind of thing. Take a look in your supermarkets and other large retail outlets. Have you ever wondered how they get the floor so flat? They fix the tiles first then hone them flat using machinery and increasingly finer diamond pads.

You dont need to re-tile if the existing ones are sound and just lost their sheen. What you need is a specialist contractor who will re-polish the floor using diamond pads and re-seal. I know a UK company who does this kind of work at home and abroad. Message me if you want his details.

If you're going to fix tiles, on no account use pva on the plaster/plasterboard. Its completely the wrong thing to use.