Thorfun

Yep. Makes perfect sense. I’ll make a mental note to check it when we get to that point in the build! Thanks.

thanks @PeterStarck for confirming that I did understand what was written! I've come to the conclusion that the company I spoke to that won't use Posi-joists as they've had bad experiences with deflection on them maybe didn't install them at the correct centres or didn't add strongbacks. either way, I'm convinced I'm happy to go with Posi-joists.

this is interesting as our decision date is fast approaching and I was thinking that coronavirus is a great excuse for the planning department to ask for an extension. I might ask the architect to speak to them to get a feel as to how they're running things at the moment. despite how frustrating a delay would be, I would fully understand it (and honestly am fully expecting it!) as I'm not completely without a heart.

our architect has mentioned that maybe we could think about entering in to awards once the build is finished. I assume from that that he's very happy with the design he came up with (as are we). fingers crossed the planning department like it and we can get it built. then we can think about awards but it's something we hadn't even considered until the architect mentioned it.

so I finished reading (or flicking through) those 2 docs @PeterStarck linked (the Steico one was really dry and a tough read) but from what I can gather deflection isn't an issue unless you're getting to the limits of the specified beam and so I-Joists could also have deflection issues as well as Posis. It also seems that reducing the centres will reduce the deflection (is that correct?) as it makes a stiffer floor. so if one company is offering posi-joists at 600mm centres and another at 400mm centres then the floor with the 400mm centres will bounce less. is that also a correct assumption? The posi-joist brochure also talks about Strongbacks to reduce deflection so these can be added (and from the reading should be over certain spans) to assist. in fact, assuming I understand it all correctly, using Strongbacks on Posi-Joists results in less deflection ( span * 0.003 ) than the I-Joists (stated deflection of span * 0.004). this means for a 4.5m span the deflection of Posi-Joists with Strongback results in a 13.5mm deflection whereas the I-Joists would be 18mm. again, this is all assuming I understand it correctly! all of which means I'm feeling better about not having a trampoline on the first floor if I use posi-joists. ?

probably not very helpful but I'd get the architect (assuming you're using one!) to see what they think. but I would probably look to put it as close to the purple line as possible so you've got at least some south facing garden although I presume that your access is from the south so some of that south facing garden would be a driveway and garage. it might be nice to face the house east to west though to take advantage of the views but, again, as close to the junction of the purple/yellow/red line as possible. but, I would definitely seek the advice of a professional. then again, I don't have the knowledge nor experience of some of those on here so hopefully someone more helpful will be along soon. ?

we're awaiting planning permission at the moment (decision due in a few weeks assuming that happens due to coronavirus) and we're still planning to progress as normal. we're in a strong position in that we're living in a bungalow onsite while the build will progress so if things take a bit longer to arrive due to the supply chain then so be it but I don't see it as a reason not to start at least. As John says, we can get the foundations done and order the TF and windows once a confirmed date for the TF is obtained etc. but everyone's situation is different and what works for us might not work for others!

indeed it has. https://national.homebuildingshow.co.uk The National Homebuilding & Renovating Show has been postponed The Homebuilding & Renovating Show has been following Government guidelines regarding the continuation of our event surrounding the outbreak of Coronavirus. However, as the news has been progressing we have listened to the concerns, from all parties, around the health and welfare of their staff. As a company we are becoming increasingly concerned for the wellbeing of our visitors, exhibitors and staff, and as this is our first priority, we have taken the extremely difficult decision to postpone The National Homebuilding & Renovating Show at the NEC, until the Summer. We are now working through the ramifications of this unprecedented situation. Please bear with us while we try to establish new dates. We will be in touch with all our visitors as soon as we have more information to share.

Thanks Dave. I don’t mind the extra costs for an easier first fix. I’ll probably recoup some of the costs in saved labour costs anyway. Which is why I wanted the posi joists.

just a little light reading, hey? ? I'll crack on with that. I know people on here have used I-beams and others have used Posi Joists. I like the idea of Posi Joists for the ease of first fixing but if there are potential issues using them then why do people? would this simply be a companies preference or (with my cynical hat on) a product they make a higher margin on?

Hi all, we're in the process of getting quotes for timber frames and one company is offering I-beams rather than Posi Joists. The say that they prefer to use the Steico engineered I-beams as they have less deflection than Posi Joists. now, if I knew what that meant I might understand it! But as I don't I was wondering if anyone can explain what that means and whether there's any concerns or if it's just simply not true or something that doesn't need to be worried about. cheers.

Thanks @pocster. I really appreciate it. Now I know they come in triple glazing I’ll definitely book a showroom visit. We also have a double height entry hall with Windows front and back all the way up. I think IQ should be good for that structural glass type thing as well, at least their previous project photos show lots of that!

it's good to know that they do triple glazed units! it's really not clear from the website nor the spec sheets I was sent. they sent me the Sieger Legacy, Sieger Slim Casement and Sieger Slim sliding spec sheets. did you go for the Sieger range?

@pocster sorry to resurrect this thread but I've had a quick look at IQ Glass and I'm struggling to see from their website that they offer anything half-way decent! I've been sent technical data sheets and can't find a good performing inward opening window and no mention that I can see of triple glazing. what windows did you order and how are you finding them? I think I need to visit their showroom to see what they have as it's not too far from us but, at the moment, I'm struggling to justify even that short journey.

my architect suggested waiting until we had planning permission before getting this survey. But I’m thinking we should get it now as even if planning is rejected the plot has permission for a new bungalow obtained by the previous owner so even if we build that we will need a geotechnical survey. So I can’t think of a reason not to get it done now. Assuming cash flow allows it of course! But welcome the thoughts of others.

Welcome! I’m also a new member but have already asked a number of questions, read many blogs and learnt a lot, but I’ve still a lot to learn. I’m also looking at building a basement and the big basement post @Bitpipe mentioned was in response to a post of mine. Some great info and can be found here:

wow! thanks so much @Bitpipe for taking the time to give such detailed information. there were a lot of questions there and I'll try and go through them and answer as well as I can. but I think what I can take from your post is that I'm not even close to being able to get a decent quote from someone for the basement. I think I need to be more patient, it's just I've got 8 weeks of waiting for planning to respond so thought I'd use it wisely to get rough quotes in so once permission is granted (ever the optimist) we can make a decision and crack on! so naive I know but you've got to let me live in ignorance for a while yet. like yours it's just off square under the house (it's a part basement) at approx. 9m x 8.5m but it has a sunken external courtyard as an outside space, to let light in to the basement and also to act as a fire exit (which should answer some of the other questions you asked about light and BC fire exits). here's a basic plan. no wet services as we didn't want to bother with that. any guests who need the bathroom can go up the stairs and there's a toilet up there. I haven't decided on the roof of it yet. we do want UFH on the ground floor and also want good sound insulation as the music room will be used for my band to practise and record in so don't want the sound to travel upwards. so I'm leaning towards a solid floor even though this goes against the sustainability requirements I have. but a sustainable build is all about compromise and I will think long and hard about this aspect. again, not sure on this yet. but from initial reading, and I believe that the water table is very high where we live (our neighbours have a cellar/basement built recently-ish that they use for food storage so not really habitable and they said that the water table is above their basement (which is surprising as we're on top of a hill). anyway, when I get the geotechnical survey done that will tell us all) so I will probably have to go with Type C waterproofing with Type A tanking as a belt and braces option. so I would assume we would insulate the slab and also the internal walls in-front of the Type C waterproofing layer. but I have lots more reading to do on this subject. again, I would probably defer to the 'experts' on this but I'm leaning towards poured in-situ using movable formwork. We have just under an acre on the site but the existing bungalow takes up a bit of that space but we do have plenty of space to put/fit plant on site during the build. The sunken courtyard is closest to the existing bungalow and is about 6m away which should be enough that sheet piling shouldn't be required to support the hole. nearest neighbours are between 50 - 70m away I think so no concerns about party walls! we will most likely need to de-water but I'm hoping that the planets will align and we'll break ground before the end of the summer and so the rain might have stopped by then. thanks for all the other information in your post. it is noted and I will revisit it many times in my journey. this is a very valid point! it did seem that they were pushing Type C waterproofing but I'm not so naive to be led down that path without further investigation and double checking everything first. I will request a quote from them anyway to get a comparison but as has been previously mentioned, personally recommendations count for a lot and so will bear that in mind when making a final decision. I have a good friend who's father works as a QS for a big groundworks company and he has already said he'd get him to get me a quote. so this is definitely a route that I will be pursuing. thanks again for all the excellent advice. I know I have just started on this journey and still have a long long way to go and I'm trying to fill the time waiting for planning approval in a constructive and educational way. ?

I understand what you're saying and will take it on board. thanks. thanks. I really don't fancy tackling form work! any recommendations on who I could contact initially? or should I just Google it for now and then do more research?

yep. I need a self-build mortgage at the financial institution I've been speaking to do indeed need their surveyor involved from the outset to sign everything off during the build.

the company I spoke to at Build It Live use an internal membrane to manage water ingress just like you've described. I'm sure I could fit it and do it all but what about future saleability (not that we plan to move but you never know!) or getting a mortgage? wouldn't they need some form of sign-off that it's all been done properly and given a guarantee?

agreed. I've read a lot about @Bitpipe's basement and will, if it's ok with him, send him a PM to get the name of the company he used as he seemed very happy with their work.

would be very useful to PM it if that's allowed. cheers. we're in West Sussex south of Gatwick so South London is not that far.

this is what scares me and why I'd want a specialist or at least someone who will guarantee their work, not just the concrete pour. if it wasn't for all that I could probably just ICF it myself.

sounds good, but scares the cr@p out of me as it sounds like a lot of responsibility on my shoulders to get everything ready for the pour. or am I completely misreading this? I'm alright at DIY but building a basement is a bit beyond my confidence levels.

Hi all, our planned self-build has a basement that will be a habitable area consisting of a music room and a games room/entertaining area. the ceiling will be 3m high as I have an idea to put a golf net and simulator down there and need the height to swing a golf club! I am at the point where I am looking to get quotes for the work and was wondering if those that have had basements done are able to recommend their basement contractor? Also, I was as the Build It Live show in Kent the other weekend and spoke to a couple of chaps from Surrey Basements who seems to know their stuff and looking at their website seem to have done a large number of good looking basements in the London area. does anyone have any experience with them? any opinions are, as always, very welcome. many thanks in advance.