Deflection (I think) when / how to worry/react.

[chrisforsterx]

Hi, I'd already made a post to do with having a multi gym in my bedroom. and was getting a lazer measure to measure the "Deflection" if any, in the floor below.
from what I was told I should only get about 2mm deflection in joists. Based on weight / space used etc.

I intend to measure the ceiling before gym setup, everyday for a month once setup and depending on how much, reduced to once a week, if no deflection.

I'm about 50KG overweight and expect to take 18-24 months to lose weight.

Even if everything goes ok. Does any know at what speed a long term deflection should be noted, concerned about.

As an example, if the 2mm is immidiate or within 2 to 3 months, although i would keep more frequent readings. Is there a change speed that's considered ok to keep weight on floor knowing I'll take down in 2 years. Through to, need to remove immediatly as will cause long term damage or worse, in a short time. Like will 2 years of weight on floor cause damage.

Thanks.

 

[oldbutnotdead]

For every metre of clear span you are 'allowed' 3mm of deflection.
You can load the span up to that limit pretty much permanently- you will still be in the realm of elastic deformation (so if the load is removed the timber will return to its starting point).
Exceeding that limit can put you into plastic deformation (where the timber is permanently deformed and does not return to its starting point). This is bad, but unlikely to happen unless there is gross overloading (like 5 times the design load gross). Timber also gives you plenty of audible warnings (unlike steel or concrete).
IMHO you would need to have a rethink if the gym on its own exceeds the 3mm/metre.
You would also need a rethink if the creep (slow progressive deformation) reaches that limit

 

[chrisforsterx]

For every metre of clear span you are 'allowed' 3mm of deflection.
You can load the span up to that limit pretty much permanently- you will still be in the realm of elastic deformation (so if the load is removed the timber will return to its starting point).
Exceeding that limit can put you into plastic deformation (where the timber is permanently deformed and does not return to its starting point). This is bad, but unlikely to happen unless there is gross overloading (like 5 times the design load gross). Timber also gives you plenty of audible warnings (unlike steel or concrete).
IMHO you would need to have a rethink if the gym on its own exceeds the 3mm/metre.
You would also need a rethink if the creep (slow progressive deformation) reaches that limit

Also for anyone who could reply.
Thanks, sorry took a few to reply, as can only get chatting on weekends. Thanks for the other answers as well. I just wanted a new post as it was getting confusing with many replys.

But I also wanted to check. I've built a platform that's approx 2m by 1.8m. top layer 11mm OSB bottom layer 10mm by 10cm by 1m planks spaced by 10cm and diagonally placed as I don't know the direction of the beams.
I've started setting it up and only half of the weight is in the room, there was already that amount of weight that had been there for years but I took it out.
Other posts talk about jumping up and down on a bedroom floor, I've been too scared for that but have just bounced and felt the floor move/ seen shelves shake. Today one of the parts about 20kg was standing on end 80cm long and 20 cm high and 8 cm thick. It fell over On the platform and I was on the platform and felt the floor move. I don't know if I'm catastrophizing / worrying.

Do you think that's normal. It's is a 2006 new build.

 

[oldbutnotdead]

You'll always get some movement in a timber floor but the scientific test is the beam deflection under load.
I take it you've already measured the no load height below (just thought- if the ceiling below isn't connected to the floor above you might get erroneous readings- might want to measure floor-ceiling in the actual room).
Cheapest easiest test static load is builders tubs full of water.

 

[chrisforsterx]

Thanks. I have measured. I'm about half way through putting it together. And measured again, no diff at about 180KG. Typical stress of self assembly, easy if you already know. But stressfull while doing.
So after 8 hrs I'll leave it and measure again tomorrow and start again and hopefully finish... And measure agian.