We had some builders in to give quotes for
1) fixing our cracked ceiling. One builder said "raking out, bonding then taping then plastering", the other said "raking out, bonding then skiming".
They do sound to be more or less the same but it rather depends on what they both mean by bonding; the may be referring to bonding with PVA or use Bonding plaster which is a base plaster prior to skimming with finishing plaster. Bonding plaster is not usualy used on ceilings except when plastering over heavy Artex patterns or if there is other damage. Are they going to re-skim (plaster) the whole ceiling or just repair locally?
Is skiming the same as plastering? is bonding without taping is good enough?
Skimming refers to a layer of finishing plaster (around 2-3mm thick) but you can also have base coat plastering of which Bonding plaster is one product but it’s not usual to use a base plaster on ceilings except when plastering over heavy Artex patterns. The cracks/joints must always be reinforced with fibreglass tape or it will crack open again. It’s also important that they find out why it’s cracked & rectify that problem as well or it’s very likely to happen again. Could be any one or more of a number of reasons, the most common being that the original nails used on old ceilings are no longer supporting the ceiling boards adequately allowing them to move & sag; this is usually rectified by re-fixing with additional screws. There could also be movement in the joists or, if there’s a loft above, by storage or people walking around up there.
2) puting on new tile on our bathroom. The cheaper builder said "remove tile, skiming then tiling" is skiming enough for tiling
I rather depends on what the walls are made of – dry lined stud, dry lined plasterboard or plaster over blocks & how much damage is caused when the tiles are removed. Removing tiles from plasterboard usually leaves it in such a mess that it’s quicker & easier to replace the plasterboard & start again rather than trying to repair the damage. With plastered block walls, quiet often all that’s required is to rough fill any small holes in the finishing plaster & then re-tile directly over that but sometimes large areas of the finish plaster will come off with the tiles requiring a re-skim. If your really unlucky then all the plaster can comes off the wall back to the blocks with the tiles meaning it will have to be completely re-plastered or dot & dabbed with plasterboard but that is the least favoured option IMO because if it is not done properly using the correct materials it won’t last. A look through the tiling & plastering forum archive posts will help you understand a little more about the options open to you. Or if you post back with more info on the above, specific advice can be given.
