Basics of drylining a loft room

[glasgowdan]

I've a few very very basic questions and wonder if anyone could help please? I'm learning all of this as I go having no experience!

I have taken down the old hardboard and polystyrene ceiling in our loft room and have got it all insulated now with 70+50mm rigid board. I have left the hardboard walls in place and just renewed the flat ceiling plus the 45 degree eaves portion of the ceiling.

Now I need to plasterboard it all and I've never done this before. I have the positions of all of the rafters marked out, and just want to get to grips with a few things first:

1. Do I start on the walls or the ceiling?
2. Should I use 9mm or 12mm board, given that the rafters are around 400mm apart, but it'll almost all be sitting against rigid board or hardboard rather than 'floating' between the rafters?
3. The whole lot will be skimmed. Do I need corner tape on all the inside and outside corners?
4. How long screws should I buy? They have to go through 50mm insulation plus 12mm board, then some small areas that had the odd gap here and there. So 100mm?
5. Taper plasterboard for everything?

Also, not quite plastering, but I am building a partition wall to create a sectioned off walk in storage area. Do I put this up first or plasterboard first? Perhaps I need to build the framework of the wall, then do the boarding work, then board up the wall afterwards?

How do I make sure the wood at the bottom of the stud wall is directly below the top?

Any help would be really great as the youtube videos I'm finding are too non specific to a job like this!

 

[vinn]

1. ceiling.
2. 12mm
3. tape inside corners and use skim bead on outside corners.
4. Are you saying that you've pulled your ceiling and walls out by over 100mm?
5. No. square edge.

Note/mark where all your joists and studs are.
Board the room out, and skim it before erecting the partition. Board the partition after its been fixed in place.
Drop a plumb bob or use a straight edge and level.

 

[glasgowdan]

Why would square edge be better if I can ask? Do I still scrim the joins?

 

[vinn]

Tapered board is for a different finish but if you have it it can be used.
You scrim all joins.

 

[glasgowdan]

I do like the idea of having a bare board finish to paint, but with an awkward couple of bits around the dormer, would taper board leave these bits looking a bit wrong?

 

[vinn]

Tapered board is taped and jointed with compound - its not usually skimmed.