Moonshine

It would have if he had applied for CIL exemption before he started work, which is what you have to do. However as they are built i don't think that there is a method to retrospectively apply for exemption.

Mortar at the base of the cavity is not usually a problem on open cavities unless the is a gas/pollution membrane at the foot of the cavity (at floor level). If there isn't this in place then mortar will just drop down to the oversite level and not a big issue acoustically. The big issue acoustically comes where there is a gas/pollution membrane at the foot of the cavity and the mortar gets trapped and the brickies don't clear it out. A way around this is to keep blocks out at the base of the cavity to allow cleaning of mortar droppings.

no he is not, use resilient ties wall ties (Type A) correctly spaced (i.e. not too many of them). What @Mr Punter is describing is too much mortar build up / snots on the ties will cause bridging of the cavity and reduce the acoustic performance of the wall. This is particularly of note if using insulation slabs / roll in the cavity as careless brickies can let build up happen on top of the insulation slabs / roll which causes issue. Edit: if you find things like below, you want to be having a lot of words with your brickies!

Yeah, this is my bag. Assuming it's 100mm cavity, put superglass or isover party wall roll in there. If you want some more detailed advise send me a message with some drawings

No where am i going against what any SE is advising (i haven't even appointed one yet ?), i have two different potential solutions from two different engineers who have quoted for the job. The figure i have included is just an illustrative section of what the arrangement will be when built.

How about. 20-25mm PIR boards? cut to size with a knife and wedge / fix in, expanding foam around the gaps. When dry cut the expanding foam flush, and plaster over. A photo would help

The final solution will be, but one response that i have from an engineer was that, in the area i am in the ground conditions are good. I am getting quotes for ground investigations and the results of these will go to the structural engineer for them to design to.

26 weeks today, and no decision and there won''t be one issued today either as we haven't had draft pre-commencement conditions to agree to. However i know that the case officer is gathering information to set conditions, so its highly likely going to be an approval once the decision gets here. I doubt there will be a request for extension of time today, but if there is or in the future i am going to politely refuse given the last extension (<26 weeks) didn't get achieved. I will also highlight that if i wanted to i could appeal under non-determination, as the previous extension was not achieved, but i don't want it to come to that.

Thanks for this, as it helps me visualise what is needed, as i hadn't really know what would be needed in terms of temporary works

Oh I am not trying to design it, I just have two different potential solutions from two different engineers and I am trying to work out in my own head the construction phasing of each and the cost implications.

Not saying it is, I have quotes from two structural engineers one with one potential solution, one with another.

I am trying to get my head around possible construction solutions to the situation below, one structural engineer is recommending piling, the other is going for a hit and miss retaining wall. As below a proposed basement of the new house is under the party wall act of an existing house (mine), and the retaining wall needs to support the existing house (the blue dotted line is the proposed boundary line). The thing is this is only an issue for 3-4 metres and other than this the other 14-16m of retaining walls are fairly 'simple'. Obviously there needs to be a retaining structure, the questions is. what is the cheapest and easiest way to build it. my gut says that piling is overkill for such a small section when everything else can be conventional, with excavations made behind the wall line

cheers

it doesn't give one, as its just a example project.

Thanks, i have seen them before, would you be willing to send me what you got from them, unless its pretty much like this https://www.estimators-online.com/sample_files/Self-Build-detached-dwelling-SMM-Client.pdf

Any you would recommend?

If they are in Cornwall I doubt it would be a plot cost as a limit as in non blow in areas, plots are fairly reasonable. Could they have been built as holiday accommodation, that didn't work so sold as individual dwellings.

Interesting graphs, and I agree that the 'acoustic' in a name does give a up lift in cost when it's the density you are really getting. High density boards are needed as they offer the higher acoustic ratings needed in some situations (e.g. trying to meet ADE conversation requirements on a timber floor with limited floor to ceiling space). Also as you say labour, people will start looking at you funny if you start asking for triple boarding, when you could do it in a double layer of SoundBloc. @Dreadnaught in simple terms a single skin partition with double the density will increase the sound insulation by 6 dB In the mass control region, but maybe more like 4-5 dB when considered throughout the whole frequency range. See below

It will be interesting to know if this is required now to support the application, or will be conditioned for pre commencement. Could save the OP a bit of hassle and risk of £ spent if it's a pre commencement condition with app granted.

15mm does not equal 2x12mm of the same density. No the joints don't create significant weaknesses. Resilient bars are good over direct fixing, just make sure you use the right length screws, especially if double boarding.

Shame its not an air source heat pump as you can get this under permitted development for a domestic application (see MSC 020), assuming its less than LAeq, 5min 42 dB at the nearest receptor. In regard to Westminster they are pretty hot on noise, and i have experience of them requesting acoustic assessments, but rather on a load of plant, though a requirement for a singular external condenser unit can happen. They will be looking for an acoustic report to address the requirements of Westminster's UDP Policy Env 7, see https://www.westminster.gov.uk/unitary-development-plan-udp chapter 9, page 440. If you have to get an acoustic assessment done, you will need to get someone out to measure background noise levels and provide them with details of the unit you want to install. The acoustic assessment will compare the background noise measured with the predicted noise levels of the condenser at the nearest receptor, and assess against the requirements of UDP Policy Env 7. Typically an external condenser unit will emit LAeq 52 - 55 dB at one metre.

If you are only looking to get an equivalent level of acoustic performance from the OSB, then look at getting a similar surface density from the liner board, below is a link to the surface density of many plasterboard sheets. If you are using standard 12.5mm Gyproc wallboard thats 8.0 kg/m2, the OSB / ply thickness should be matched to this surface density. OSB has a density of around 640 kg/m3, you will need min 13mm boards to give you a surface density of 8.3 kg/m2

So i think that i don't have any case for a refund via the planning guarantee, as i have agreed an extension of time which is over the statutory 8 week period, but before the 26 week period. https://www.local.gov.uk/pas/pas-topics/planning-applications/decisions-positive-planning-agreements-extension-time From the above it appears that any extension of time over the statutory period is considered "an extended period" not the 26 weeks. So it seems any agreed extension over the statutory period means that you invalidate the planning guarantee. Edit, i now believe this is wrong, and the extension is over the 26 weeks

you wouldn't on MVHR's but for big AHU's and plant you do usually need an attenuator on the atmospheric side if you have noise sensitive receptors around.

phew, phoned another place which is £270 for a 20T in 2020, which is a bit more in the realms of what i was expecting / hoping for. @Red Kite thanks for all that information, and plenty for me to digest, cheers This is where i am at the moment, i have the topo survey which i created a 3D sketchup model of, and now i have a final planning house design, i have been able to work out the cut and fill volumes as below (may need refinement once the structural engineer has designed it). This is about 320 m3 in total, which for cost estimates i have added a contingency of 20% for the development currently has a out the ground m3 with contingency of 380m3. I haven't had a bore hole on site yet, and am in the process of arranging (waiting on specs / locations from a structural engineer), but know that its likely to be sandy from a historic bore hole 200m away. Assuming a sandy soil weight of 1800 kg/m3, and a 20T truck (well 19T load), that's 36 loads with the muck away at just under £10k (TBC). I need to get a soil/borehole survey arranged with screening for waste characterisation, asbestos, and WAC. This will go on to the SE who then can design the foundation/retaining walls, and then i can get that to the GW contractor to price the job. However in the mean time, i want to start getting a feel for what the GW cost is going to be.