Richard & Tracy

Go to Mapei.fr and look for Mapei G, first in the stone and tile section then the primaire section. This is what you need to prime plaster or sand/cement surfaces prior to tiling. I daresay there are other brands out there including Ardex.

Large format tiles are very popular nowadays. I dont know what the regs are in France but the British Standards state the safe weight limit on plaster is 20ks per sq mtr so one assumes that a similar figure would be appropriate anywhere else. Cement and cement based products react adversely with plaster and so the plaster should be primed with a tilers primer, not PVA. If the walls have a shiny finish you should roughen them up a little to provide a key. A sander would do the job. What type of tile are they? Different tile types need different adhesives, trowels and applications. Let me know me if you want any more information.

Use a cement based (Bagged) standard setting adhesive, not a fast setting one or you will spend half your time mixing and waste too much. Look for one that is classified EN12004 C2 or C2E. These are the european standards. Use an 8mm notched trowel. Trowel the adhesive onto the wall with the straight edge like you were plastering then comb it out with the notched edge whilst holding the trowel at 45 degrees to the wall. On no account try and comb leaving a thicker bed, you are guaranteed to have some tiles proud of others (lipping). Assuming the substrate is flat, combing correctly will ensure no lipping. Push the tile into the adhesive with a twisting/sliding action. Occasionally, pull a tile off to check you are getting adequate adhesive coverage. Dont grout until 24 hours have elapsed and use a flexible one, EN13888 CG2. Dont use the shower for 5 days after grouting. The 2 most important thing are a) making sure your substrate is flat before you start and b) setting the job out correctly. By setting out as described earlier, you will know where all your cuts are before you start and you will avoid the 'oh bloody hell' moments when your 3 quarters through and find you've got a difficult cut. You could do all your field tiles first, to give you some confidence, and do the cuts last.

1. You must use a cement based (bagged) tile adhesive with a large tile. This cures by chemical reaction whereas a ready-mixed adhesive(bucket) is air drying and therefore with large tiles, the adhesive in the middle will never set. 2. When using a cement based adhesive, you must prime any gypsum plaster or plasterboard to prevent the adverse chemical reaction that occurs between the two. Do not use PVA, its completely the wrong product. You must use an acrylic primer dispersion specifically made for tiling. 3. When fixing tiles greater than 300mm x 300mm you need a thicker bed than 6mm, probably 8 or 10mm, and you may need to back butter too. This is to ensure a full coverage of adhesive. 4. What are the tiles made from. Ceramic? Porcelain? Stone? Different materials require different adhesives. 5. Consider the weight you are fixing to the boards. About 30kgs per sq mtr is considered safe. With plaster the safe weight limit is only 20kgs per sq mtr. With some porcelain and natural stone, you will be on the limit. Make sure the boards are securely screw-fixed to the background. 6. Using a spirit level, mark a continuous line all round the room at a convenient height avoiding any obstructions. This is your datum line. You will need this to determine the highest and lowest points of the floor and ceiling. Then using a spirit level, draw a vertical line on each wall. From this you will be able to determine if any wall leans in or out. Then you can start setting out. 7. When setting out for width, you will find it easier to find the centre ot the wall and tile off the grout line or half tile, depending on which gives you the larger cut into the corner. 8. When setting out for height, remember the floor may not be level so test a few different positions starting with a half tile off the floor and adjust accordingly depending on where other cuts are (window reveals, bath, shower tray, etc). 9. Once you have determined your starting point, using a spirit level draw a horizontal line all round the room. This is your tile line. If you follow this, your tiles will meet up correctly in the final corner.

Yes most are suitable for use outside but worth checking with the supplier just in case. Yes they need to be sealed. The traditional method is to use boiled linseed oil and then a polish afterwards. Some are more porous than others so just keep applying it until the tile wont absorb any more. If the tile is not very porous you can thin it with white spirit. Generally, leave 8 hours between coats. Dont let it dry on the surface. Its better to seal before grouting because as its so porous, the grout is liable to stain the tiles. LTP is a good product but there are a few others incl Lithofin and Aquamix.  

You can make walls flatter to tile on by overboarding with plasterboard or tilebacker board.

Hear hear.

The Aquapanel has a polystyrene core and is great for going onto a concrete floor prior to tiling to provide insulation and a good surface to tile onto. However, I dont think they are rigid enough for a timber floor so I would recommend these instead: http://www.pureadhesion.co.uk/product/172/10-x-hardibacker-250-(6mm-floors)    

You know that movement is the main problem so thats a good thing. There are a couple of ways you could satisfactorily tile these rooms. In either case, ensure adequate ventilation beneath the floor. 1. Cut out the floorboards, insert noggins between the joists to stiffen them up and re-board using 25mm thick WBP or marine ply, having sealed the underside and edges with primer to prevent moisture ingress. The ply should be screw fixed to the joists and noggins at 300mm centres. 2. Screw fix the existing floorboards at 300mm centres, replacing any unsound ones and punching in any nails as you go. Overboard with cement based tile backer board (stagger the joints), ideally 10mm thick but you can get it in 6mm thick, again screw fixing at 300mm centres in each direction. Fix the tiles with flexible cement based adhesive preferably 2 part, although single part flexible may be sufficient. Grout with flexible grout. Ensure a movement joint of 5mm around the perimeter. Method 1 would be my choice and will give a minimal step up from the adjacent room which, when covered with a suitable transition strip, will be virtually unnoticable.

You need a penetrating sealer suitable for stone for the dust problem. You will be able to get it at a tile/stone shop. PVA will sit on the surface and make the stone a little shiny.

How much do these wood based pellets cost?

Be aware that virtually all grout commonly used is cementitious and therefore water resistant NOT waterproof. This means that it is not affected by the passage of water but water will certainly pass through. If you want a better solution you should use epoxy grout but this is still only about 99% waterproof. The best bet is to tank the substrate prior to tiling. Cementitious bathroom grout and kitchen grout is basically the same though the bathroom grout may have some extra anti-bacterial properties added to it during manufacture.

Electric under tile heating is one option and it gives you more space as you dont have radiators on the walls.

There's no such thing as waterproof grout. The nearest you can get is an epoxy based one but even that isn't 100% waterproof and it's much harder to apply and clean off than normal cement based grout. I'm afraid that the only permanent solution is to rip it all out and start again.

Shower cubicles 'leak' because they aren't done properly. Grout is usually water resistant, not waterproof. Meaning that water will pass through it but not damage it. So the water passes through the grout to the tile adhesive and on through to the substrate then it runs down the wall behind the shower tray, often appearing as 'tea staining' on the ceiling of the room below. Also, by this time any plastered background will have been damaged because plaster is very water sensitive. That is why, when you remove tiles in a shower or around a bath, they usually come off easily bringing the plaster off too. The best thing to do is to tank the walls prior to tiling. That is, apply a waterproof coating system. These include a membrane that ensures any water runs back into the shower tray. A simple and inexpensive way of ensuring a lasting installation.