G and J

I posted this in another similar thread a few days ago…. ”Welcome. In ‘91 we bought a plot, got full PP, and I promptly got quotes from several builders. The most highly recommended of which called me a moron. He had asked me why we didn’t build it ourselves, getting in trades as needed. I answered “well I’m not in the trade”. That’s when he called me a moron, but he was smiling. He said “if you’re in the trade you know one trade, so you have to learn the other ten. You have to learn an extra one - so what? “ Sage words it turns out, and that was before YouTube. Get in there. “ I suggest doing the main contractor thing may be right for you for many good reasons, but I suggest not being in the trade is not a good reason. We start demolition in just under two weeks. F Scary. F exciting too. Soon after that we start building what will be our second self build and I’m principal contractor and principal designer, may god help us. Oh, and when we did our first self build, with no main contractor but helped hugely by some really great guys, I was in IT and had no experience whatsoever.

Been looking into this for our meter kiosk install. EV point is right next to kiosk but house is further and I’ve been advised to whack in a 110mm twin walled flexi duct to future proof. I’ve also been told to go 25mm2 armoured cable to get tiny voltage drop (circa 10m). Could you just drop in a large duct to defer your decisions?

It all started with a concerted, sustained effort to reduce ‘stuff’. Our cupboards are now a lot emptier and we are happier for it. Then Tuck came along. He’s our (air) friar, mostly as an experiment in saving energy. Quickly realised how many of our meals I can cook with just Tuck and a microwave. Then came along da bungalow. When we planned the kitchen, which is visible from everywhere in our single big (comparatively to the rest of the house) room that we will spend most of our time in we thought about how we use our current kitchen and how that could be improved, that’s when I realised I wanted an invisible hob. Then I saw the price tag. Then I started thinking about and experimenting with no hob cooking. For me it’s quicker, cleaner, and suits our diet and psyche. No frying, some veg batch cook and frozen, no meat, smallish portion for just us two, few simple carbs (especially at home), etc. In parallel with all that we thought about making our kitchen area pleasing to the eye - for us that meant simplicity - qooker tap, no kettle, virtually nothing out on display; it also meant symmetry. Then when the question of location of dirty great big smudge of a hob came along our answer formed - it’s a tiny version hidden away till needed. So it’s not really about energy saving any more. It’s about how we want to try and live and how we want our environment to look.

All viable options. But no, no hob in me kitchen, just a little portable one in the utility room for occasional use.

Interesting. Will research.

Very good plan. Again, thank you.

Noted. Thank you.

Is that still true of a single easy bend?

Laterally, vertically, or both?

You could be describing the design for our new house. Re reduced worktop height, be a bit careful. Make it just a tiny bit too low and backache ensues. So I’d advocate prototyping it before committing. Our main kitchen area is part of the big room (kitchen, lounge, dining and conservatory). 2.7m worktop flanked by full height cupboards (larder fridge freezer on one side, oven, microwave and coffee cavern on the other). Sink in the middle of worktop, no wall units and no hob. Neat. Lots of storage in the utility room plus a portable induction hob for when I give in and use one (batch cooking mainly). Yes. When thoughts began re living without a hob I started experimenting with non hob cooking, mainly because I think even whizzy induction hobs are v ugly - a big dark lump in my nice light coloured worktop. We’ve a gas hob on our range cooker now and it’s surprising how easily I have found reducing hob use. Maybe that’s partly as I never cook meat, and I fry nothing, but it’s quite liberating trialling new ways of doing stuff.

Thank you - and Amen to the airtightness. I really appreciate all this guys. I want to explore this debate re what goes under the insulation. Before that I want to check understanding and put the drains issue to bed. Whatever goes under the insulation my poo pipes are going in the insulation and above my main DPM, assuming my BCO is happy with that. That means I can have a 100mm screed plus UFH or 120/150mm construction slab with UFH. Good news. I just have to have enough insulation to house the pipes allowing for their falls. I'm thinking I can use the insulation to carefully manage the falls to make sure I've got no low spots due to pipe deformation, so safe to use long lengths of plastic, if needed rotated to make sure any bend in the pipe is horizontal and not vertical and thus does not affect the falls. Is all that correct?

And presumably as long as it is of even thickness I can put a lot of EPS down there.

So the drains sit in the EPS layer above the DPM. Presumably one tapes up the penetrations and it’s all ok cos my plumbing is good enough to ensure no leaks.

I am one with special needs lol So now I’m thinking 120-150mm slab on 300mm of EPS with all drains completely within the EPS. Don’t yet know where the DPM goes, don’t know if I convert to bnb for the back half of the house as the ground falls away and there’s no drains, don’t know how I support the poo pipes, but hey, a ‘don’t know’ shopping list is a start.

I actively want a slower response in the sense that I want the screed/slab to hold enough heat to enable reasonably consistent internal temps using cheap periods of a ToU tariff.

Took me so long to write my last post I missed this one lol…. Re the BnB yes, it simply doesn’t work with our drain levels. The only alternative I knew about was a concrete base, then insulation, then screed. However, I now am starting to understand a constructional slab (I think it’s called). As soon as I thought about pipes in insulation I had a wobble. The insulation goes above a DPM and if a pipe leaks even the tiniest amount one has a pooey underfloor pond trapped in a DPM tray. Not a pleasant thought. But where does (do) the DPM(s) go in a constructional slab? Is the build up…. Crushed, compacted stone, sand blinding, DPM, EPS (with added pipework), Vapour barrier Slab with UFH. Or is it…. Crushed, compacted stone, sand blinding, (is this needed if there’s no DPM there to protect?) EPS (with added pipework), DPM (which also acts as a vapour barrier), Slab with UFH.

Totally agree re the process of working back from the road - here’s my thinking in case I’ve made a mistake…. The existing manhole on site loses ~100mm, so that’s going. I set my datum as the target finished floor level. Against that the invert level near the edge of site is 625mm lower. If when we dig all the way to the edge of site it’s lower still that would be a bonus, but the pipe there appears to be at 1:80 already. Guessing a location for a manhole for the join of the two branches places it just west of our short wall. That’s 6m along and at 1:80 that loses 75mm of invert. The southern branch, from the base of the soil stack, carries WC waste so can be at 1:80 in 100mm pipe. There's 12m of that so at 1:80 that loses another 150mm, giving 400mm max invert level against FFL at the bottom of the soil stack. The other branch does not carry WC waste, just sink and overflows. Therefore min fall in 100mm pipe is 1:40. For a 10m run that means a fall of 250mm. With a 150mm pipe even without WC waste a much shallower fall is allowed, up (or is it down?) to 1:120 I believe, but using a sensible 1:80 that gives a drop of 125mm so that’s better even allowing for the pipe being 50mm bigger. Thus Mac invert level against FFL the bottom of the AAV stub is 425mm, but it’s a bigger pipe hence the top being closer to FFL. I’ve been over and over that and if I’ve hit that wrong and it’s not as bad as that I’d be annoyed with myself but chuffed to bits.

I think I’m getting the idea. So that would place the base of the insulation just below the top of my soil pipes. Is that ok? Would the DPM be below the insulation (to avoid soggy PIR) and simply rise over the pipes?

In this case I think it’s a case of me not knowing what I don’t know. Like big time. In the above example were all the internal walls were supported by foundations? Do the concrete/UFH slabs (is that the correct term?) all have a PIR upstand round them? If so is it a smaller one for internal walls for expansion vs a larger one on external walks to reduce cold bridging?

The regs seem to say otherwise. I think it’s the whoosh of the flush that allows less of a fall. In fact you want less of a fall to ensure that the liquids don’t leave the solids behind. A 10m run of 100mm pipe that doesn’t carry toilet waste must have a fall of 1:40 = 250mm The same run in 150mm pipe can have a much lower fall (say 1:Ip124ay or 1:100) and thus help when things are tight.

We had intended to have a beam and block floor. If we went for a slab above insulation what would the build up be? We are having strip foundations. It’s not sensible to have a raft due to the slope of the site, we’d need a stepped raft which would not work easily.

The 150mm pipe run does not have a loo feeding it so if it was 100mm pipe it would have to have a fall of less than 1:40. That would really muck the levels up.

Interesting idea, and that shows the power of the lateral buildhub mind. It would help the run length a bit, and probably increase the invert level on the 100mm pipe by about 40mm but unless it dog legged quite a lot between the joists it would impede the room upstairs. I guess the question in my mind is can I have me pipes that high in the slab?

Fair point, but I was hoping to avoid a pump. I like gravity, it doesn’t blow a fuse or need maintenance.

I need help with my drains.... We have a strong view of where our finished floor level should be, which is of course bad news. This is driven by our need for our new pad to look right in the row and not cause offence as we want to get on with our neighbours, cos we try and be nice peeps. But, the sewer pipe at the edge of our plot is not deep. I had hoped for a 100mm screed and 200mm of PIR as underfloor insulation, but that now looks highly unlikely. So we've ended up with the below as my best guess. I'd be grateful for comments and opinions and ideas - is this design OK? Where can it be improved?