Bigdeadbadger

Thanks saveasteading, Re the ends of the building - yes, I have trenches in my design around the perimeter of the building that will allow the wind/venting up to the surface (2000mm2 per linear meter off the top of my head ) , but can only get to that as I look at backfilling in/around the slab at a later point. Cheers

I have just been through this very topic over the last year or so in Central Scotland. First recommendation - challenge everything. My experience here is that the "worst" case scenario is typically assumed with limited justification especially from 3rd parties. In our risk adverse world, I experienced people making (faceless) choices based on those worst cases vs what might actually be a more pragmatic approach. Had I challenged more - I would have saved time and money. As part of my planning application, I was required to do a phase 1 desk survey, which highlighted my plot was a low to moderate risk of unrecorded shallow mine workings (not uncommon for this area - like mentioned in earlier responses) and potential for ground gases. This outcome then placed a requirement to do an intrusive phase 2 site investigation as part of my planning conditions - including 6x boreholes for ground gas monitoring. Based on the phase 1 desk survey, my site was allocated an initial CS2 rating by my local councils 3rd party contaminated land consultant (noting my council outsource this work). It's at this point - I wish I had challenged more, as I feel in hindsight, this was excessive. Having obtained quotes for the phase 2 survey, a couple of things jumped out. The cost was ~£6K as per examples listed above and the monitoring period was over 3 months. Based on these costs, the potential for ground gas to be discovered anyway, and a naïve thinking I would be ready to build soon and the monitoring would hold me up, I took the decision to include a Gas Membrane in my slab design and accept a CS2 rating in Lieu of the gas monitoring. And that is where things got really fun, as for me, it was not just a case of "just" including a membrane. Instead, I had to: 1) for my building warrant, I was expected to provide a Contaminated Land Response, detailing how the Gas Membrane would be installed, and how the design met BS8485 2) not only was a membrane required to meet the points allocation needed to pass CS2, I also needed to demonstrate my slab was reinforced with minimal penetrations (pretty easy) but also then design in a passive ventilation layer below my slab (all of this is in BS8485). Giving me a points score of 4 (target was 3.5) 3) detail how the membrane would work along side my insulated raft formwork 4) provide external 3rd party validation of the membrane installation in line with CLA:IRE guidelines 5) my BC could not answer ANY questions on the topic. All discussions went via their 3rd party, had to be via a "design" and typically had a 3 week turnaround. Based on being thoroughly frustrated at this point due to many things on my build, I actually composed document 1) myself by getting hold of a copy of BS8485 and demonstrating a compliant design. I did not obtain costs for a 3rd party to do this, but I would expect low £ thousands as its (rightly) outside the scope of a SE and Architects specialization. All in all, by the time I include the Visqueen membrane, the labour, the 3rd party verification, the cost of the low fines gravel ventilation beneath my slab, I will have spent ~£10K. I sleep at night, by convincing myself that bore holes may have found ground gas, and I would have then spent and additional £6K on monitoring and I didnt spend extra on someone else designing the solution. BUT - some pictures below to show it can be done Low fines material for ventilation (this was quite expensive) - 300mm deep, 260m2 (my house is going to be quite big - ground floor at 200m2). Could be cheaper going for preformed venting sheets from the membrane manufacturers. And installed below my formwork (still to be dressed on the sides of the formwork). Excuse the mess. Hope that helps

Thanks for the details Kelvin, i'll give them a buzz although maybe too far for them (West Lothian) , but agree with your sentiment. Earlier searches I tried were also unfruitful because builders were (understandably) cautious about engaging before BW was approved. Now that is has been approved - it doesn't seem any easier!

Hello BuildHub, I was looking to see if anyone had any recommendations for groundworkers in/near central Scotland - looking to start asap. Currently having limited success with cold calling - so any recommendations would be appreciated. Building Warrant in place and ready to go - insulated slab. Thanks

Thanks folks for the suggestions. Re contamination, no idea, it’s farmland that’s been fallow for 30yrs.

Contamination of soil / gases , basically drilling a 5m borehole, taking a sample, and doing a drainage test. Thanks

Morning All, As a condition of planning approval, I need to perform a site investigation survey. I was curious if anyone had any recommendations on companies to contact. I have had one quote so far @£5k and nearly fell off my chair. Thanks, Andrew

I would be as well if possible. I’m starting out getting quotes for these same group of SIPS suppliers, so any extra insight would be greatly appreciated. Thanks