oldkettle

3.5K+/m2 you call subtle? ?

Does anybody know whether basement raft can have a step in it? May be cheaper to add plenty of steel into this than deal with Party Wall.

What can I say... Great to be able to work like this (not a hint of sarcasm here).

I wonder whether architects here would care to comment. What strikes me about these homes is that they are very similar and in many cases seem to choose form over the convenience: I seem to remember cantilevered parts present a significant cold bridging problem. But again, that's for a professional to confirm.

Thanks everybody, I've almost lost hope I'd get more replies. @Bitpipe Actually I've been going through your posts on the basement yesterday evening. It did cross my mind that this was an option, we are already 2.1m in the ground from the dpc level and I'd happily lift the FFL another 0.5m. What stopped me eventually was your note that an extra meter of width was required for the excavation. In our case that'd mean moving another 2.3 metres to the left which would certainly upset our neighbours on the left. My wife is also not keen: "why do you need an extra 100m2 in the basement on top of the 50+m2 outbuilding". I feel like we are back to square one which is extremely frustrating. @Russell griffiths I understand a retaining wall is needed, I am just trying to figure out whether the existing wall can serve this purpose to an extent : somehow it has not moved anywhere nor allowed the slab to move. @Russell griffiths @Alexphd1 I thought I didn't really need to build the ground level up as it is already there, just remove the slab and about 500mm below and start building back up from there. Am I wrong? Off to read about topo surveys.

Yep, I understand I will need multiple holes. But it is likely that the one at the lowest corner will end up being below their foundation in the middle, so I wonder whether this is a problem.

So no need to ask them first? I would of course let them know as we have good relationships. What about the stepped issue? What if the hole at the lowest point goes below the foundation 3 meters up?

Hi, Attached pictures show our existing wall and the neighbours' garage about 1.8m away. I am trying to understand a few things. 1. If the Council Building Control won't find any documents showing foundation depth, is excavation my only option to establish this? And based on the slope does it mean I may have to dig in multiple places as it can be stepped? Am I allowed to start digging without serving any notice as long as I don't go below the bottom of their foundation? 2. We want to extend at the back well beyond the length of their garage. How does 3m rule work when there is nothing on their side when we draw a line perpendicular to the border? Or is it 3m regardless of an angle? 3. For those who had a basement and was affected by the Party Wall Act : how expensive were the extra steps, technical and legal? Thanks in advance.

Yes, I remember, Dave. In our case the ground has been there for 60+ years so nothing needs to be added... hopefully.

Hi, Found a somewhat related topic (https://forum.buildhub.org.uk/topic/567-passive-slab-and-sloping-site/) but with a much smaller difference in levels than ours. As you can see from the attached pictures, we have quite a fall currently. Close to a meter back to front and >0.6m left to right. The right wall sits well above the ground with 14 courses of bricks below dpc only. So now that we are almost ready to accept the inevitable (demolish and rebuild) I want to understand whether there is a reasonable chance to build a raft here. One builder mentioned the existing walls can be used as retaining/supporting the perimeter, but he didn't see the pictures. The concern is obviously the cost: if we are going to have to start adding piles etc. this may become too expensive. Party Wall act may also come into play. Any clues or do I need to go straight to Hilliard?

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Thank you, @AliG The problem with strip foundation is that it would have to be really deep and potentially require a SE design due to proximity to the row of conifers. Alternatively we'd have to step away from the border even more which is not impossible but would have been disappointing. Basically, we are trying to decide where to live during the build. A container or a caravan are not good enough for my wife and would be a pain to get into the back garden anyway. Renting would easily gobble up 20K in 12 months. A gym sounded like a good idea, especially since in the last 16 years I've spent close to 10K on those. Another option is half and half, much smaller gym (to avoid BC) which we could use during the day as home office/lounge and a caravan in the front garden for the night and meals. Basically, I'd rather spend 25K on a basic build than 20K on the rent. Actually, had a reply from a planner regarding temporary accommodation permission. Completely gobsmacked as what he describes sounds like a full planning application where as I would only need lawful development certificate in the worst case scenario as can build under PD. >> As you acknowledged in your email, a temporary planning permission would be required. Whether this would be granted would likely depend on the scale, design and siting of the outbuilding envisaged. The application would take the usual statutory period of 8 weeks to be determined. So as you can see, nowhere close to finding a solution at the moment. Will keep thinking. Have no interest in another planning battle.

10-15% I'd accept. It's 800 vs 400 (+12% prelims) which I find OOT.

it may well be - I didn't check, the only link I found was https://www.hanson.co.uk/en/ready-mixed-concrete/technical-information/concrete-pump-faqs >> Concrete pump hire costs can vary but, as a guide, expect to pay around £300-£400 on top of the price of the concrete. If this is the case 800 (+ VAT) is another nice little earner. Or rather not.

Absolutely, there is a window in the rear garage wall, an opening can be created there as well. Depends on what needs to go through - what type do you think is required? I thought a 1.5t digger would be enough as there is very little to actually dig so didn't worry too much as it's only about 1m wide. The garage roof will have to come down as it a corrugated asbestos cement one, for now it's a storage + while there is a door it add security. I was planning to do it when the main building works start as will probably make putting scaffolding there easier.

The bungalow is not coming down fully, PP is for an extension. Do you mean a dumper truck? This is a big beast. When talking to builders I always tell them I am open to suggestions regarding access. £800 + VAT for a pump isn't a small change but rebuilding a garage is not going to be cheaper.

well, the access is not too bad - surely can get 1.2*2.4m panel through easily and for ICF this wouldn't be required. But can't do without a pump. Roof I certainly want pitched, need more height for the gym I remember single skin construction was discussed here a while ago. Need to try and find robust detail for it, see whether there is a way to have an uninterrupted insulation layer with the roof. Also make sure rats are easy to keep away - a building which in not used 24/7 will be under constant threat.

You said 40% off - I thought the initial price was twice what I expected nearly there. Yes, I won't touch concrete whatever happens. WRT cavity wall, not sure it would save me enough. If I spend 10K+ on the passive foundations with services it probably makes sense to complete this properly. SIPS panels and ICF seem to be £50/m2, I need about 30*2.4=72m2, doesn't seems to make a huge difference, maybe insulated b&b would be 3K rather than 4K here? Or am I well off here?

What insulation are you planning for the open panels?

@PeterW, @ProDave Well, I am not sure about concrete, but since we want to live there during the build I thought making it into a well insulated one would make sense. I do indeed want to use it as a gym eventually (and the kids have other ideas for the extra space) and want to avoid cold floors in winter and really hot air in summer. Yes, it would be way more economical to use pads, although due to the proximity to the trees these may have to be really deep (with this size I have to involve BC). With regards to the build method, I started with SIPS as one of the producers was happy to quote for both the extension and the outbuilding, but right now I am seriously thinking about ICF: 30m perimeter, one floor, must be possible to DIY in a reasonable time. Don't need anything special inside, just MDF or plywood, a couple of internal walls. I am not sure at all about the heating and hot water though but one problem at a time. There is access for a mini-digger on the right of the house, just over a meter wide. There is also an option to create an opening at the back of the garage, then obviously a larger digger would be possible (although the height may become a limitation). I did a quick search and it seems due to the very limited excavation any mini-digger should be able to handle it. Peter, this is what I thought about the drains. Even if it is required in one place, certainly shouldn't be 3. Seems just a way to inflate the quote to me - but again, this is why I ask others to advise, don't know nearly enough.

Sorry, there are none: he came around to look at the site, took some measurements and provided a quote in a few days. The project is to build a 9x6 gym at the top of our garden, and take services there (and foul water back). This company has quoted for the groundworks part. As I said, there is a fall of about 2.5-3m from the top point towards the house and the distance is about 40m. There may be a gentle turn or two on the way to arrive at the corner. Attached is a very very rough drawing of what needs to happen.

I thought excavation for the whole trench was a separate item anyway? Or is more work required specifically for chambers? With regards to backdrops, I read a bit on pavingexpert and not sure whether this applies, as I'd expect only the "source" in the outbuilding and a single connection to the existing system, this may be the place where one is needed? But again, "include connection into exiting chamber" is a part of the excavation line.

You are certainly right I found the first company around here who have insulated raft on their website. Wanted to get an idea of the cost. They completely ignored my "300mm EPS" message, no idea why hexatherm has been quoted. Yeah, I went through several posts about the slabs including DIY ones and saw the guide prices you mentioned, just hoped to find something with a reasonable price here, otherwise my wife will switch back to "we should rent" and I really don't want to live in an apartment ever again: even caravan sounds better to me.

Prelims - you are probably right, but this looks really steep to me - this is a company specialising in ground works and "managing the job for 10%" is something an architect charges for getting to site once a week. Anyway, won't be questioning this number. Skips were apparently for timber shuttering and steel offcuts. I thought concrete wasn't allowed in a skip? Anyway, they are happy to leave rubbish in place Foul would probably go to a minimum required depth, our site is sloping in the right direction at about 1m in 15 so may need to be slightly deeper at the start to arrive back to the house with 1:40 fall. I guess the trench needs to be deeper for the mains water anyway. Am I way off with my 2 days estimate? They are quoting chambers and back drops at £450 a pop - seem to cost about £200 normally? Surely doesn't take a plumber half a day to install each of them? I wanted an idea about the cost. £27K (inc. VAT) makes the project not viable. £10K - as Russell has referenced and which I kind of hoped for - would have been more like it. Will obviously get more quotes.

80mm insulation for £3348. Nice.