Max height between Storeys?

[Gimp]

So I'm looking to do a basement car park that has a floor to ceiling height in excess of the 2.7M described in Part A of building regs. At the moment my only thought to possibly get around this is to do a false timber beam ceiling below the actual beam & block ceiling level to bring it to within the 2.7M with a void in between the two ceilings. Most ceiling I know have a small void, particularly timber ones if not only to reduce sound penetration than for services. So was wondering if anyone has any idea if this would be ok with building control or the best way around it. I am looking to have a void of around 450mm or so. Its just really to start the house above it at a more preferable height given the landscape & the surrounding view. I guessing that building control would just generally view the room height & not get too picky about full investigation of heights unless it seemed pretty way out, the plans of course for FFP would have the correct total building height.

 

My only thoughts on this so far is that their must be some leeway along the way as some people do double height ceiling rooms but I can't find much info around on any of it to tell me one way or the other the best way forward on this.

[Temp]

As I remember Approved Document Part A basically says... "If you build it like this it will meet the Building Regulations". However you are free to build anything you like if you can convince Building Control that it also meets the Building Regulations. So I see no problem with having higher ceilings provided Building Control are happy. To do that they may want evidence that someone like a structural engineer has approved the design. I would just ask them if what you propose is ok.

Edited October 14, 2016 by Temp

[Gimp]

Sounds a good idea Temp, I'm going to have to go to a structural engineer anyway for the whole design, for the basement garage retaining walls & weight of the whole thing to the load bearing ability of the soil, etc. So might as well get the SE to do the work there as well as since they will be working out the size of the retaining wall to height, etc it shouldn't really be anything much in the way of extra cost for them to work it out for a higher height than usual.

 

Like you say I think if a structural engineer approves it, it will be ok as I'm guessing its a height to wall ratio issue with regard to load bearing, so thinking it through now for a standard wall BC probably go with the 2.7M rather than a issue or differences in height of buildings for aesthetic reasons. Since it is probably only going to be an extra 450mm or so with a SE approved solution it should be fine. I was just afraid they might stick rigidly to it as the only way to comply with regulations in that case since it doesn't state any other option in the regs but like you say they are just one way to comply.

 

I'll put forward the whole design for outline planning permission first with D & A Statement & see how that gets on with my proposed build height, then get a structural engineer onto the job for the FFP so I know exactly what I'm dealing with, with specific sizes of wall & heights, etc. End of the day once the BC drawings are in and they have accepted them then they shouldn't be able to go back on it if its all been accepted I hear so should be ok. Many thanks Temp, you've helped clear my mind on this one   

[Temp]

In my experience Building control are generally far more helpful than planning. Planning messed me about for over a year and then agreed my original proposal (long story). Building Control allowed me to get away with a window that was slightly too narrow and another with the sill slightly too low when it would have been difficult to fix either.

[le-cerveau]

My house has a larger that standard ground floor 3.3m between ground and first floor! that is 2.75 ground floor, 150mm service void 250mm pre-stressed spans & 150mm screed (I will be less, but that is the planning figure).  But I also have 8.7m spans so that doesn't fit in with the standard BC guidelines.  The whole house is being specified by a SE (current work) in preparation for BC submission and my architect is not concerned.

[Gimp]

9 hours ago, le-cerveau said:

My house has a larger that standard ground floor 3.3m between ground and first floor! that is 2.75 ground floor, 150mm service void 250mm pre-stressed spans & 150mm screed (I will be less, but that is the planning figure).  But I also have 8.7m spans so that doesn't fit in with the standard BC guidelines.  The whole house is being specified by a SE (current work) in preparation for BC submission and my architect is not concerned.

Ah, good to know, looks like Building Control are a bit at ease so long as an SE has checked it out. I've dealt with them briefly in the past (extension thing non new build) and guy seemed to have a bit of leeway here or there. So my real fear about them sticking real rigidly to the rules may be unfounded, thew  

[Tennentslager]

Must admit I was so confused by this height stuff I decided to measure the walls in the flat I'm in at the moment.

3060mm.

It's one thing I love about Glasgow tenements. This one is about 100 years old and walls are 600mm thick.

I reckon the height was to accommodate the tall windows to get maximum light in 

[Gimp]

19 hours ago, Sensus said:

 

At risk of stating the blinking obvious, Part A is to do with structure.

 

The limit of 2.7m shown in Approved Document A is (mainly) to do with ensuring that the structure is stiff enough, overall, against wind loads (which is why it's next to a wind map of the UK). If you're in a basement situation, then you're not going to be getting a whole lot of wind, but in any case, as Temp has said, you'll be fine so long as your Structural Engineer's calculations prove the design. For above-ground storey heights of more than 2.7m, the solution is to increase the thickness of the external walls and/or ensure sufficient additional buttressing, but leave your Struct. Eng. to worry about that.

 

As Temp has also said, the 'Approved Documents' merely set out one path to compliance. The actual Regulation is the bit in green (see page 5), which for structure, paraphrased, basically says 'thou shalt design buildings that don't fall down'. The Approved Document shows a 'generic' method of compliance for masonry buildings up to 3 storeys, but you can diverge from the rules it contains, so long as you prove that your specific design still woks.

 

Obviously, the fact that the Approved Document only covers masonry building up to 3 storeys doesn't mean you can't build more than 3 storeys, or in timber, steel or concrete frame, either - there would be a shortage of skyscrapers in our cities, if that were the case - but again just means that you need to 'prove' the structure by calculation.

 

 

 

Yeah, I wondered the same that as its a basement there wouldn't be much wind loading hence perhaps a basement can quite reasonably go deeper provide the SE does a thicker wall build up for withstanding the soil pressure. Thanks, Sensus, I didn't realise the building regs were colour coded for the actual regulation you need to stick by in green & the rest I guess for how they suggest compliance.

 

This (and the advice above) is all very useful to me, it means that I may have a reasonable chance to make the best of this build as the extra height I think will change the view from seeing the back angle of the buildings below to a nice view over the rooftops, many thanks