Hi, I wonder if anyone can help... I have just bought an old house and am looking to put a gym in an upstairs room. I have had a structural surveyor and a builder round to take up the foor boards and measure the sizes to let me know whether it can take the weight (350KG incuding me). They have come back to me and told me that the max loading the floor can take if less than 0.9N/M2 - this is about 90KG, not a huge amount more than I weigh! The flip side of this is a quote for £15k to strengthen the floor with a steel beam which clearly i don't want to/cant do. So, I have done some checking myself and am pretty sceptical of their calcs and wondered if anyone could let me know their opinion. The joists themselves look pretty big to me, they measure 225mm by 75mm and are at 400mm centres. I just cant believe that these joists can't hold more then one big person per m2, let alone a weight rack. The joist span on the room is 6m which could be the problem, the wood is over 100 years old and does not have any issues with it on close inspection. I checked the span tables for a joist of this size for domestic loading and it tells me that a span of 5.15m is achieveable - surely adding another 85cm doesnt destabilise the joist to that extent? The room was originally a large bedroom with a big double bed, desk, wardrobe etc....which makes me even more scpetical, it aso has a laminate floor laid on top of the thick od wooden floorboards which makes me think it may one have been used as a gym anyway. Woud really appreciate anyones input on this one.....cheers!
Ah, bless - such hope! You have read for yourself that this size of joist is already 'over-spanned' for domestic situations; 5.15 being the recommended max against your current 6m. And then you're going to plop a third of a tonne on it. And shake it all about. These gym exercises you plan to do - do they involve movement at all? If so, that's going to quintiple the load (I made that last bit up...) Clearly, you know the score here, but you understandably want to believe the pros are being over-cautious. Bottom line - will your floor come crashing down? I doubt it very much. You could (gently) park a car on that floor and all it would do it creak. A fair bit. But that's not to say it's 'all right'. And no way are 'pros' going to say it's ok however much you may want to hear it. Used as a gym, will the floor shake and vibrate a tad more than you'd like? Will the ceiling downstairs develop hairline cracks? Will those trying to watch tele downstairs want to lynch you? I'm guessing 'yes' x 3. So, go ahead. You'll probably 'get away' with it. Probably. But don't come crying to me if...
Thanks for replying Devils Advocate. Good points you make....it was quite shaky below when I had someone jumping around up there! So the surveyor is now getting some builders to quote for bolting steel 12mm plates to the side of every joist, both sides. Do you think that will stop the noise and celing cracking issues? Cheers.
It'll certainly help a great deal. Impossible to say in advance just how much, tho'. These sound like wot they call 'flitch beams', which are a sandwich of timber beams and steel plates. They are often used instead of RSJs/ steel beams for simplicity or if a tailor-made steel is too costly. I had them used in my loft conversion with no issues at all. This job sounds like one where you need to make clear what it is you are after; what it is you expect at the end of the day. Then you tell your builders that info, get them to agree - and hold them to it. This could turn out just fine the way it is, but if it isn't as good as you hope/expect, what will happen then? How will you sort this?
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