MortarThePoint

I have a downer on added formaldehyde so am planning to use 18mm OSB in the house. In the garage I have trusses rated to 2.5kN/m2 and so want to put a surface down that meets that. 22mm T&G OSB3 is a rare beast in the UK, 21mm T&G plywood is available though, or I could go SE e.g £25/sh for 25mm sheathing plywood. I've found the thickness of that SE plywood to be very variable though.

I'm seeing prices around £14-15 for 18mm OSB3 T&G 8x2 I've been paying £18 per 8x4 for SE sheathing plywood and can see £16 for 18mm T&G 8x2 What do you think of this: https://sheetmaterialswholesale.co.uk/tg-exterior-softwood-plywood-18-x-600-x-2400mm/

OSB3 prices are close to T&G plywood now. What do people think of using plywood instead?

It's not fun, but done it before. A dead man or lifter makes it possible. Much better and more fun with a helper though. Mass. Resilient Bar still needs to work in unison with an isolated mass.

Is that the 4' sizes aren't tapered, just the 8' sides? I guess it's mainly for walls then

This is a useful resource that I have just found: Stockist Guide - Construction details. It shows other makeups for ceilings and floors. Some of the other ceilings are surprising less performant than one might expect.

No price difference in the boards really. Tapered edge is all about taping, filling and sanding the joints whereas square edge would get skimmed all over

900x1800 sheets of WallBoard (9.5mm or 12.5mm) or Fireline are £3.99/£5.80 which works out as 56% of the area for 65% of the cost. Easy handling, more screws and more joins.

Condell: 15mm SoundBloc £12.32/sheet 15mm SoundBloc F £12.94/sheet 12.5mm WallBoard TEN £8.32/sheet 12.5mm WallBoard £6.16/sheet 12.5mm FireLine £8.94/sheet 9.5mm WallBoard £6.25/sheet No brainer to step up from SoundBloc to SoundBloc F (+5%) if you are interested in sound or fire. It would be harder work to fit though. 2 layers of 9.5mm or 12.5mm WallBoard are cost comparable with SoundBloc with same or higher 'area density' and lighter but longer installation and more screws.

I thought I would record some of my research into plasterboard options and hopefully people can share their thoughts. Each manufacturer has their own equivalents, but I'll consider British Gypsum for ease. They have a useful selector here. Wallboard: 9.5/12.5/15 mm with area densities of 6.3/8.0/9.8 kg/m2. Available TE and SE. Thicker boards available as 900x2400, all available 900x1800. 12.5mm available 1200x3600!! Wallboard TEN: 12.5mm, 10kg/m2, TE only. SoundBloc: 12.5/15 mm, 10.6/12.6 kg/m2. Only TE. Minimum 1200x2400. "higher density core". Moisture resistant option (SoundBloc MR). SoundBloc F: 15mm, 14.1kg/m2, TE min., 1200x2400. " higher density noise insulating and fire performance core" F MultiBoard: 6/10/12.5 mm, 6.0/8.5/10.6 kg/m2. Only SE. Minimum 1200x2400. Fire and impact resistant. FireLine: 12.5/15 mm, 9.8/11.7 kg/m2. SE and TE. Minimum 900x1800. Fire resistant, moisture resistant option (FireLine MR) also available. Moisture Resistant: 12.5/15 mm, 8.6/10.1 kg/m2. SE only available 12.5mm 1200x2400, otherwise TE. "water repellent additives in the core", kitchens and bathrooms. DuraLine: Not Available. Highest 'area density' is 15mm SoundBloc F (14.1kg/m2). 15mm SoundBloc is around £12.30/sheet. Same supplier sells 12.5mm WallBoard for £6.77/sheet. 12.5mm Moisture Resistant is £10.90/sheet. 12.5mm FireBoard is £8.50/sheet. Solo installation and handling of 2 layers of 12.5mm WallBoard may be easier than 1 layer of SoundBloc and have a 27% higher 'area density' for 10% higher cost. I can't readily find costs for 9.5mm Wallboard, but two layers of that would have the same 'area density' as SoundBloc and be much lighter to handle. 12.5mm layers of Wallboard and Fireboard combine to make an 'area density' of 17.8kg/m2 which is 41% higher than SoundBloc for 24% higher cost.

Excuse my ignorance, but what are the main reasons to dob and dab rather than wet plaster? Does it work out cheaper or is it about using insulated plasterboard?

22mm CaberFloor states it is 15kg/m2. 18mm OSB3 will be well under. As @PeterW states it's unlikely any BCO will care though.

I've found it very hard to find density information. This link suggests Egger Protect has a density of 620kg/m3 which would give an area density of 13.6kg/m2 for 22mm thickness.

As I read it Part E does apply within a single dwelling. Table 0.1a and 0.1b set out values for 'separating' walls and floors which I presume means between dwelling units (e.g. flats) and the prevailing value for floors is around 45 dB for airborne sound. Table 0.1c sets out values within a dwelling and has a value of 40dB.

So if I understand it that document is setting out a valid substitute to the Part E "Internal floor type C".