Underfloor ventilation conundrum

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vexation

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So underfloor ventilation is necessary for suspended floors - be they timber or concrete. Our extension happens to be concrete beam and block. Fine then, telescopic vents would be the usual solution to bring the vents up from below the beams up to the outside walls above DPC level...

...Except... we have level thresholds and floor to ceiling glazing. In other words, no masonry above ground to install a vent into. The perimeter has A15 Channel Drainage to stop flooding from the surrounding patio surface. This must have been solved before, but I haven't found any solutions when searching online.
 
You are glazed on all sides?
Sounds very architectural so why has this not been solved in design?
 
Can't you extend the ventilation out from the house, under patio etc, then pop up in the garden?
 
a few of these among the terracotta pots on the patio?
82653759-232d-4f88-9dfb-ce8912145768_1024x1024.jpeg

https://www.roofingoutlet.co.uk/products/190-redbank-flue-ventilator-sailors-cap
 
tomfe said:
You are glazed on all sides?
Sounds very architectural so why has this not been solved in design?
Click to expand...
Architect never really surveyed the ground levels properly. Builders having to innovate on the fly.
 
jonbey said:
Can't you extend the ventilation out from the house, under patio etc, then pop up in the garden?
Click to expand...
jonbey said:
a few of these among the terracotta pots on the patio?
82653759-232d-4f88-9dfb-ce8912145768_1024x1024.jpeg

https://www.roofingoutlet.co.uk/products/190-redbank-flue-ventilator-sailors-cap
Click to expand...
Wow. That all seems like a lot of trouble to go to.
I understand that ventilation is to prevent build up of gases like methane/radon and to control moisture levels. Can't these be dealt with by using appropriate membranes or something?
Also, there's the possibility of breaking in below the concrete floor of the main building. This gets us into a space that is ventilated but I can imagine Building Control not being satisfied with the result.
 
so, I am guessing you are in a terrace with a conservatory style extension? There's no brickwork to put ventilation through?
If not a terrace, then extra ventilation on the sides might be possible? Photos?
 
jonbey said:
so, I am guessing you are in a terrace with a conservatory style extension? There's no brickwork to put ventilation through?
If not a terrace, then extra ventilation on the sides might be possible? Photos?
Click to expand...
Detached. Just a box sticking out of a gable end wall really. The objective was to open up to surrounding patio without change in level. Seen lots of glossy ads for this kind of home improvment but when I see detail for level thresholds, they draw them up against solid slab floors like this:

level-threshold-image.jpg
 
In that case, the old part of the house can have ventilation put in the sides. But, that diagram seems to show a slab, rather than a suspended block and beam floor. So should be OK?
 
What have Building Control said , and what does the architect say about this ?
 
jonbey said:
In that case, the old part of the house can have ventilation put in the sides. But, that diagram seems to show a slab, rather than a suspended block and beam floor. So should be OK?
Click to expand...
No, that diagram was the only example I could find detailing a level threshold. I found a few like that but they were all drawn for solid oversite slab. I'm beginning to think I'm blazing a trail here :eek:
 
Creating a suspended sub floor without any means of ventilation is certainly a problem. Was the project professionally designed, or was it a DIY job?

What stage of building are you at? Is it finished, or still just starting?
 
Leofric said:
What have Building Control said , and what does the architect say about this ?
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Hi Leofric, I'm waiting on word back from the Architect via the builder. Still on the lookout for crowd-wisdom in the meantime as I feel sure this must have been figured out before. Building control can be a bit random in my experience. I can see some unimaginative solution being presented like bringing up a couple of brick heights to form a low wall just for the vents. Don't want any of that.
 
jonbey said:
Creating a suspended sub floor without any means of ventilation is certainly a problem. Was the project professionally designed, or was it a DIY job?

What stage of building are you at? Is it finished, or still just starting?
Click to expand...
I paid an Architect several K so I hope it was professionally designed. The trouble is, they didn't account for the site levels which are sloping in all directions. New patios are not part of their plans which simply assume a level site 150 below existing dpc. At the moment we have foundations poured and the blocks laid to dpc height. Beams yet to go on. When the blocks got to dpc level it became apparent how the slope of the site favours a level threshold for the main opening onto the garden. If it was all set out as per the drawing the patio area would have to be sunk below ground level which is not something I want to see. Rather than excavate we would rather build-up where the ground falls and use perimeter drainage channels as per the glossy pic above.
 
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