Oz07

I'd put the dormers in if it were me then apply for NMA if the council spot it. Surely they've been put back in their box by the inspector now anyway so they'd be reluctant to throw their weight around. What's relationship like with neighbours

Wait till you see the price of materesses

@JohnMoare you including land costs in the 1800 or is that on top? I was just making the point that here you can buy all signing dancing properties on good plots for 4k m2 all done and dusted. Annoyingly I'm interested in a plot which is currently available at auction, and it just seems a terrible time to buy all things considered. They are rare round where we live at the minute in a good school catchment so might have to hold my nose and buy it.

Yes

Even the nice houses round here aren't going for much more than £4000m2. I'm talking great spec, great location. Seems its not worth building atm if prices to build are as high as they say. Just about to offer on a plot next week too...

min 1 in 80 with 4" pipe and at least a loo plumbed into it i think. I'd be wary of going any less on 4" pipe. Has to be steeper if it's not getting as much flow down.

There aren't maximum falls anymore as I understand it. PVC pipe did away with that

Just do plan A I bet the BCO approves. Plan B looks messy to me

Ive encased in concrete before but not sure its nessecary. See so many sites without any protection and nothing ever happens. I knew lorries would be going over so played it safe. See how many reduce dig for new driveways exposes drains that work just fine without protection. I think its probably more important to have a tight trench with minimum pea gravel needed to comply if under a driveway.

Eliminate the 45 bend after the y branch just position the y so you are coming straight up with a 90 possibly with a short straight stub of pipe between them

That's good to my eyes. If possible where that 110mm pipe comes up for the basin in the far corner can you build an accessible boxing then you could have an access plug into your pipework and rodding access in the unlikely event it was to block. Otherwise you can keep taking the pipe out thru the building on that opposite corner. Will it be high enough to clear the trench concrete by then? Then put external rodding eye. There is an argument to say keep the shower on its own separate run into the manhole then you have no y branch down stream from toilet. I think you'll be fine though. You could even cock the y junction a bit so its not flat and the branch to the shower is sticking up a bit, then immediately put a 15deg fitting on to take the pipe back level. Should give you a small stepped invert. If you've seen a flush invert manhole its really no different to a flat junction and the man holes don't just spontaneously block up. Where is the resident plumber @Nickfromwales?

Maybe just one run and eliminate the bend before the main run exits the house. It'll be easier to do because you can align with basin instead of wc

I don't think you will find a certified 45mm pair maker but you can Google it. I doubt building control are switched on enough to realise a pair maker isn't fire proof. Fire doors as doubles usually just meet in the middle with 3mm gap and intumescent strip in 1 face. You can do this, get sign off, then if 3mm gap really bothers you reduce doors down to allow pair maker

Rather than having your wc coming into the top of the run like that put a y junction in on flat below the slab then bring a 90 up thru the floor. The poo will slide down the pipe better then rather than falling into the top and the water running away from the solids. It will prob work ok your way but I'd rather my way. You have a rodding access upstream so the y under the floor could be accessed if ever blocked.

Bloody hell you seem an expert yourself 🤣