I have quickly drawn up a plan of the proposed layout (not to scale). I am proposing to add a horizontal run to the existing soilstack for the toilet waste (which will pass under a window; would that be an issue as from what I have read the only restriction if that the vent on the main stack has to be above any open window?)
Personally I would not mount the loo & sink at angles in the corners like that unless they are specifically corner units; takes up much more space, difficult to provide support/fixing & looks a bit odd with conventional units IMO. I would also move the loo so you can go straight out through the wall in line with the stack; no bends to get blocked & no roding access needed on the bends. No problem running the soil pipe under the window but if there is there another loo connected to that stack, you must have a minimum 200mm offset betwen the old & new connection.
No dimensions shown but there are limits to maximum length of unvented pipe runs (Part H); go above & you will need mini AAAV’s or HEPVO traps. You will probably need those on the sink/shower anyway if your going to connect the waste runs into the main soil pipe; separate runs to the stack for each is best but in your case would be a little silly to attempt. For a single w/c it’s 6m to the stack, any more & you will need in internal AAAV on a stub stack in the loo. I would consider the position of the shower; swapping it for the sink may give easier waste runs (which direction are the joists) especially in 50mm which I would suggest for the shower; you can then use 40mm for the sink which is OK unvented up to 3m; 32mm is limited to just 1.7m.
In regards to building regs I am a little unsure what needs to be regulated and when. From what I understand the following regs apply:
* ensuite must provide adequate ventilation (the ensuite is being added to a section of the room with a window, so I presume this would be fine)
Part F. You don’t have to have an opening window but you must have an extractor fan, min 15 litres/sec most of the smaller ones are around 20 litres/sec.
* electrics in the space must meet part P regs (the shower is going to be a mixer added to an existing combi system, and I will get a spark in to install a light, and from what i know they can self certify
As you say, Part P. In theory you can DIY the electrics but must notify LABC in advance when you make the Building Notice submission. In reality many authorities break their own rules & will not inspect, test & issue certification leaving you in the difficult situation where you then have to find a registered spark who will do it retrospectively which they are not allowed to do & actually breaks the terms of their registration.
Make sure the spark is actually registered & gives you a minor works certificate which will detail the work & results of testing; he will also have to wire the fan.
Do you have a modern consumer unit? How old are your electrics?
* drainage and waste regs (joining to existing drain, ensure correct fall etc; will be getting plumber to do this part)
Part H. Again, make sure you get a plumber who actually knows the Regs & knows what they are doing; not always the case.
* sound insulation in stud wall between ensuite and bathroom (install celotex/kingston/rockwool and double plasterboard on bedroom side?)
Interestingly, sound insulation only applies to any stud walls between the w/c room & another habitable room – the bedroom next door, you don’t have to insulate any walls forming the en-suite in the bedroom it serves; so it’s OK for your partner to hear you fart but not the person in the bedroom next door!
If you need sound insulation for the studs, you must use Wallboard 10 as a minimum both sides; ordinary Wallboard does not meet the spec. unless you double up on thickness. Many (including myself) use 15mm Soundblock which is even better. Minimum for the insulation material is 25mm mineral wool, I used cavity insulation bats which my BCO was quiet happy with but check.
Is there anything I have missed? Also can this all be checked in one building inspection and covered by one Building Notice or do I need to get it inspected at each stage?
No ground works are involved because your connecting to any existing stack, BC are unlikely to want a test so will probably just visually inspect at the same time as the waste runs; your probably looking at one stage inspection + completion inspection. LABC fee is linked to works cost but is unlikely to be more than £150; you can download a form & list of charges from the CNC website;
http://www.cncbuildingcontrol.gov.uk/applications.htm
Sorry for the barrage of questions but the whole regs thing really hurts my brain!
Sometimes sticking pins in your eyes would seem a more gratifying experience but they do get easier to understand with experience & you’ve got it all covered. You can always ring your LABC for guidance one you’ve submitted & paid your fee (they don’t really do free consultancy) & there is usually someone on the forum with relative experience.
