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Weight capacity of wooden joists for installing recording booth in flat

Postby breanting » Mon Aug 24, 2020 9:59 am

I’m looking into buying a recording booth to put into my home studio in a first floor flat. The booths I’m looking at weigh from 611kg up to 886kg (138x175cm) and I’d like to know if my floor can take that kind of weight.

The wooden floor joists are 370cm long, 5cm thick, 15.5cm wide and 40cm apart, meaning the booth will be sitting on roughly 4 joists, and will be situated in the corner where the joists meet a supporting wall.

I have a heavy-ish large table, a sofa bed and a bunch of recording equipment in the room, and will have usually no more than three people in the room at a time.

Is there any danger at all of the floor not being able to hold all of this weight? Anyone who has experience with this kind of thing would be much appreciated.

I’ve attached a floor plan below.

Image
breanting
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Postby stoneyboy » Mon Aug 24, 2020 8:58 pm

Hi breanting
According to current building regulations your existing floor is good for around 25kg per square metre. If you were to increase the joist sizes to 19.5cm deep the design loading would then increase to 125kg per square metre. Even this is approximately half the weight of your booth.
Suggest you need to take professional advice from a structural engineer.
Regards S
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Postby breanting » Mon Aug 24, 2020 9:49 pm

Thanks very much for the reply stoneyboy. I'm finding it difficult to translate 25kg per square meter into real life terms, as I'm 82kg and presume I can stand in an area much less than that and not give the joists any issues, but I guess there's some sort way of calculating this.

I think you're right though, it's probably a good idea to get some professional help just to make sure. I thought I'd see if anyone had experience with something like this on here first.
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Postby stoneyboy » Wed Aug 26, 2020 3:10 pm

Hi breanting
Looking back at the pre-70's building regs your beam size is ok for 25-50kg/sqm. Taking the higher figure and your floor area you could put a total distributed load in the room of about 550kg.
The issue is that the joists may have been notched on the top and/or holes drilled through them, this reducing their load bearing capacity. For this reason and that there is presumably another flat below you, a structural engineer must be involved and this may mean floorboards have to be lifted.
Regards S
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Postby breanting » Wed Aug 26, 2020 11:07 pm

Thanks again stoney, that clarification does put things into perspective. It really seems like the floor's not made to support something that heavy. I definitely wouldn't want to mess with the downstairs neighbour's ceiling.

I've gone ahead and contacted a few local structural engineers for some advice, I'll report back here with any findings and if I do get any further with this. Thanks again!
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Postby breanting » Mon Aug 31, 2020 11:55 am

Just thought I'd post my findings here. I've consulted a structural engineer and his analysis of the existing joists in accordance with the requirements of the timber design code (BS 5268-2:2002) concluded that they have insufficient capacity to support the resultant loads from even a small 434kg booth. He said that "unfortunately we require to satisfy the loading and timber design code requirements". So I guess I'll have to wait until I move and find a place with stronger floors (it's not worth it to reinforce my current floor if I'm moving in a few years). Thanks a lot stoneyboy for helping me out too, it is much appreciated!
breanting
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Postby stoneyboy » Tue Sep 01, 2020 9:14 pm

Hi breanting
Many thanks for keeping us posted - hope you find somewhere suitable.
Regards S
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