Bitpipe

I got a quote from these guys early on as I was thinking of doing the basement in ICF so explored doing the whole house that way. https://thermohouse.co.uk/

Welcome - we also had committed to a design with PP etc before stumbling onto this site (well, it's predecessor) and deciding to make our build meet passive standards - which we achieved, although it's not certified. By luck we had more or less the right orientation and glazing design and didn't need to tweak things too much, mostly adding external blinds to minimise unwanted solar gain. We also went down the timber frame package route as we were managing the build ourselves and got a full airtight, waterproof (once glazed and roofed) shell to passive standards from a single contractor which made the rest of the build pretty straight forward. We mixed things up slightly by building a passive basement instead of a ground level slab, but the principals are the same. One thing to consider is ensuring the follow on trades don't undo the work that has gone before them to make the envelope airtight - it's not hard to achieve but needs continuous attention to detail (and sometimes supervision).

Local friends who build a basement practically in the Thames used the Glatthar Fertigkeller system which is precast, pre-insulated and also waterproof. I think they use WPC for the sections, a special grout for the joins and a thick membrane which may have been sprayed on (or sprayed over, can't recall). Their main design challenge was stopping hydrostatic pressure pushing the basement out of the ground, as a result their slab was ginormous. Full turnkey service, design and build, comprehensive warranty but very expensive (we got quotes).

Totally agree that a major consideration is if if you want to DIY or get a contractor to handle it. Standard formwork and shuttering is definitely not for the faint hearted and looked to require a lot of experience and equipment. Also a 3 sided basement will be more manageable than our four sided big hole in the ground. Regarding the economics that I experienced, I would not have been allowed to build any bigger above ground as was restricted by ridge height and already was exceeding the original house footprint by a significant margin. Planners did not blink at basement, which increased the internal floor area by almost 50%. Being in SE England, the land prices are such that £1000/m2 is quite good value. Also, I should really offset the cost of the basement against a passive slab or traditional strip foundations (we have 1m of clay on gravel and chalk) so the incremental figure is less than that. Doesn't include fit out though but that was not a huge number as it got rolled into the rest of 1st/2nd fix and finish.

I think you'd struggle to get a waterproof join between those. The contractor I used knocked out my 110m2 basement with 42 liner metres of 2.5m high walls in about 3 weeks and not even the slightest sign of a breakout but they were using industrial quality shuttering and were very experienced. Rebar work was impeccable too (all 14t of it) they even spotted a few mistakes in the SE drawings which they sheepishly acknowledged when I called them up about it. The BCO turned up for a pre-pour inspection and left after 10 mins saying he didn't need to see any more Cost was about £1000/m2 - i.e about £100k for the whole basement including excavation, muck away, drainage, the basement itself and backfill with clean stone.

Our BC was happy with just waterproof concrete (Sika warrantied system) in our basement and the shuttering crew were quite fast as they built one corner piece, one flat piece and rotated them around the site, minimising the joinery time. My warranty is with Sika, not contractor. 15 years. We also have a perimeter land drain at the foot of the basement slab draining to a soak away and there is a 1m wide backfill of clean stone between the exterior insulation and the excavation. I've no doubt that ICF would perform as well, however it would still have needed additional insulation on the outside as I needed 200mm. I also liked seeing the pour quality post striking and ensuring the water bar detail was correct.. If you're paying a contractor to do this then they're providing all the kit anyway (and the expertise). Be wary of external tanking - it's only as good as the crew that install it and if you get an issue it will be hard to isolate it. With warrantied concrete if it leaks, it's their fault and can be fixed from inside.

My condition was quite modest - 45l or something - but there had to be some provision. I suppose you could ignore it on the basis that they wont check - which is not an unreasonable assumption.

I had a planning condition on providing a modest amount of RWH - water butts would have sufficed but were not to my taste. Given we had a concrete box already in situ and were able to route the rain water system to it, putting 4 IBCs in it and hooking them together was peanuts (thanks to all who helped advise on the method). Will be used in extremis during the summer but I guess that even 4000l would go quite quickly in a sustained dry spell so probably fairly pointless in all honesty but was a fun side project and helped a bit with the water usage calculation that BC require. The systems that allow RWH to flush loos etc are quite complicated to meet the regs, require their own plumbing system internally and just seem to add cost and complexity. They also need mains back-up incase it doesn't rain and there are valid health concerns about bacteria etc from bird droppings.

Highlights poor airtightness, dot and dab plastering and bodged tests - all issues we’ve been highlighting here for ever. https://www.theguardian.com/money/2019/feb/02/new-build-homes-why-some-owners-are-left-feeling-the-cold

Nope, wrong solvent. IPA is the only thing I've ever been able to shift it with...

Have some isopropyl alcohol (available amazon / ebay) handy as it's the best for cleaning hands, windows, gun, etc afterwards when the foam is still wet.

Yes, our Vent Axia Sentinel (standard BPC issue) allows you to unscrew the front cover, remove the heat exchanger and wash it out. That said - the exchanger unit is solid - a six sided cell with solid top and bottom - you can get water into it but you can't take it apart itself. I usually clean it in the bath with a shower attachment. I normally do that just after autumn when I replace the filters and give the whole inside a good clean, including the fan blades, summer bypass vanes etc. Just gave the filters a good hoover just now - I should do that every month but usually forget - try and change them every 3/4 months. Not seen any issues with condensate building up though - will double check that. Ours runs straight down to a condensate pump (no u bends) where it mixes with boiler condensate and both are pumped up to the utility room drain from the basement plant room.

Our BCO waived any requirement for external venting as houses either side had SVPs and we're on same sewer run. He said that in new developments, requirement is only 1 in 10 with a SVP.

I tried when doing my demolition in 2015, both gas and electric said no as it was related to existing services, not new supply. Always worth a punt though. Note that if you route your supply & meter to a kiosk and take the new house supply from there then you avoid paying for a second supply move.

Nope, moves and changes are VATable services. I think only supply of a completely new service is VAT exempt.

We have a recirculating extractor hood over the hob, does a good job but does get greasy inside so is cleaned regularly. Vents to ceiling level within the room. The hob sits opposite the wall ovens so in the ceiling mid way between them is a MVHR extract. We have one other in the kitchen for general extract. Our hood did not have the right connections to wire it directly into the MVHR (which does have a cooker hood boost terminal), we could have put a current sensor on the feed to trigger it but tbh the built in humidity sensor generally kicks in or I just hit the boost button in the utility. I've popped off the cover of that MVHR extract and it's not at all greasy inside but is a bit dusty - more so than the bathroom extracts but I expect that is because there are in a damper and therefore less dusty environment. Do you ever need to clean your extract ducts? Not even sure how I'd go about that...

Rip out all the copper / brass and other useful metal and take to a scrap yard - you won't get much but it will go in your pocket vs the demo contractor and is quite good fun also

We paid £7k for our 12 panel in roof system in 2015, just squeezed onto the FIT before it got completely slashed at end of that year. FIT payments are about £500, I'm obviously saving on energy usage but don't have any measurement in place to quantify that - My solar diverter to the immersions in my UVC have clocked up over 2000 KW since install in mid 2016. All that said, I had to use the firm's MCS qualified installer & electrician but that requirement is gone if you don't need FIT so any competent roofer could do the trays and spark do the rest of the install. As Jeremy says, if you go in roof you save again on the roof coverings.

https://www.planningportal.co.uk/info/200130/common_projects/43/outbuildings/2 If the floor area of the building is between 15 square metres and 30 square metres, you will not normally be required to apply for building regulations approval providing that the building contains NO sleeping accommodation and is either at least one metre from any boundary or it is constructed substantially of non-combustible materials. Our garage is Timber Frame with insulation and is right on the boundary with neighbour, but as it is slate roof and cement board rendered, this was considered sufficient to exempt it from Building regs.

Does the BCO need to approve the garage? I didn't think they were normally relevant unless attached the house or of non traditional construction with windows facing the neighbours (all part of the fire aspect.

OK, to clarify I did have a clear idea of what outcomes I wanted (mostly based on ideas from this forum) and brokered discussions between these two trades (plus MVHR if you're not DIYing that element - something of a rite of passage on this forum) to ensure they were on same page, especially where they interacted (such as heating system, fighting for first fix space, etc). I more or less left it to them and their professional judgement to design their respective systems and decide where each pipe and cable went - can't help thinking that if I had commissioned a super detailed wiring / plumbing diagram then I would have been spending twice and/or it would be ignored anyway. We also did a few site walk throughs ahead of 1st fix to make sure large services, such as foul runs, went where they could/should and didn't clash with other systems. One place where a M&E plan would be useful is during the structural design to ensure sufficient voids, steel penetrations etc are made to enable the bulky services (MVHR, Fouls etc) to be laid efficiently. We got caught out a few times on that but managed to work around issues - just.

No problem, early feb would work for me - @HerbJ is down the road and @Jeff is not much further. @Weebles are also in the area and are in the midst of building so you may want to PM them to see if any are open to a visit. You'll find that self builders are more than happy to talk about their experiences. Getting them to shut up is the hard part. I found visits to other builds, complete and in progress, invaluable. To your last point - you're responsible. Don't rely on a contract to get you out of a hole. I'd be wary of paying for M&E engineers - find a good plumbing contractor and a good electrician and get them to design and install their own systems. Also don't rely on the architect, however talented, to design you a house that you can either afford to build, is actually buildable, will be comfortable to live in or economical to run. The first two parts of your process there should happen in parallel. If you've experienced some building projects already then you're already streets ahead of where many of us were when we started! p.s. Rainwater harvesting done cheap is good for watering the plants, different story wanting to use it inside your house....

Post of the Month Ian, if not the year....

A friend of a friend is a freelance sound engineer and worked on a few of the property shows a while back (may have been the Sarah Beeney ones). He was quite straight forward - they're entertainment / drama shows, if you're not being naturally entertaining / dramatic then they'll make sure what goes on screen comes across that way. Most of them adhere to the 3 act play formula: act 1 establishment, act 2 cliff hanger, act 3 resolution. Grand Designs is very predictable on this front, even if the act 2 'drama' is very tenuous. On a related note, I read recently that the US apprentice production team had a terrible time with Trump. They'd have filmed all the task footage and prepared a report for Trump with a shortlist of who cocked up and should be fired. He never read the notes and arbitrarily chose someone from the loosing team even if they'd done well. Cue the editing team frantically re-cutting the footage to make that person look stupid and the rest good.

You're doing pretty much exactly what we did - demolish an existing and build new with basement. We're in Berkshire also on mains gas - 440m2 inc garage. You're welcome to come visit if you want to PM me. As Nick says, if you want to reduce dependency on future fuel prices then build a well insulated, airtight home with consideration to effective heating and cooling. I don't think anyone on this forum has a passive certified house but many of us have built to passive principals in order to achieve the same objectives as you and the cost is nominal compared to standard construction. I ran our numbers yesterday for another thread and we spend £1.2/day on gas and £1 on electric (after PV FIT) for our house which is occupied through the day as we both work from home. Teenage kids etc.. Most important thing is the design - the house needs to be considered as a system, not a pretty box with services thrown in as after thoughts. Your architect may or may not have the skills to do this but it's not rocket science and many here have figured it out. @HerbJ has a similar area to you I think - we used the same firms in the build but both PMd the projects ourselves (in my case with zero prior experience). It can be done