Floor load

[Bob.]

Hello,

I'm a longtime reader of these forums, about to begin a project, and would like to ask for some advice. I'm going to build a steel framed custom fish tank but have the usual questions about load on the floor.

The house is 1920's solid brick construction with timber suspended floor. The floor is 20mm engineered oak boards.

The size and location where I want to put the tank would mean an approximate fish tank, water, and frame weight of 580kg. The tank would be 800x700 so a footprint of just 0.56sqm. This would be too much for the floor as I understand it. The location would be in the corner of a room, both walls brick construction with one being an exterior wall. The tank would span 2 possibly 3 joists. I don't know the size of the joist but do know there are brick pillars under the joists at intervals.

Without getting a structural engineer to confirm, this seems far too much weight for the foot print and number of joists. Before I bin the idea or make the decision to go with a smaller tank I was wondering if the following would be viable.

As it's steel framed, would it be feasible to bolt it to the wall? I was wondering if bolting the frame to the exterior wall (double brick thickness) and then winding down adjustable feet until they touched the floor would help. I could include diagonal frame braces from the top frame to the rear upright that would be bolted to the wall. My Google is failing in trying to determine loads but my thinking is the wall would take the majority of the vertical load with the floor taking the horizontal load.

Can anyone tell me if this is just Sunday morning thinking or whether it has merit? Any advice appreciated, even if that's to get a structural assessment or a specific resource website.

Cheers.

 

[John D v2.0]

Normal design load for ground floor nowadays would be from memory less than a couple of hundred kg per m2. However that's used for calcitonin joist and board thickness, so if you site it over a wall plate it would be fine as long as the sleeper wall is in good condition. However our 1920s house the sleeper wall are just built off the dirt. So it would depend on that.

 

[oldbutnotdead]

If you bolt one side of the frame to the wall you've transferred half the load to the wall so the floor is now only taking 290kg. If you bolt the adjacent side to the wall as well then the floor loading goes down to 145kg (or maybe a bit more, depends on the stiffness of the frame).
You'd have to put spreader plates on your wind down feet to get the point load down to something sensible- or you could just put a sheet of ply under the frame, shim the wall sides up by 2mm, drill and fix frame, remove shims. There's going to be no horizontal load imposed by a fishtank unless Jaws starts thrashing around vigorously

Other option (depending on condition the subfloor is in) is lift some floorboards and prop the joists with 6 x 2 or 4 x 3- nog the joists while you've got access, all helps stiffen the floor & spread the load

 

[Bob.]

Thanks both.

And thanks Oldbutnotdead. That was my thinking, I wasn't sure how much load would the transferred to the wall but it seemed a sensible way forward to my untrained thinking. As you say, bolting to both walls seems the best approach and spread the load between 2 walls and the floor.

No Jaws in the tank, but feeding time gets a bit vigorous! My reference to horizontal load was if I was hanging 580kg off one wall, with an 800mm overhang, without floor contact. But as you say, bolt to the other wall and that alleviates some of that load especially when spreading the contact point for the feet as well.

Sounds a plan. Thanks again for your thoughts. That definitely seems a lot more comfortable than just loading the floor.

 

[Steve]

I have actual walls built on the middle of the floor upstairs in my house. Theyve been there since the 1950s. And not going anywhere soon! They must weigh a fair bit!

I saw a fish tank for sale recently which held 900 litres of water. The water alone in that will weigh 900kg. I hope they send it out with a weight warning!

If you dont plan to move this tank, like, ever, could you shore up the joists from below? Stick in a couple of fence posts directly under the joists, but wedged in. I wouldnt rely on wall fixings myself. I once saw in a shop with a cellar, a cash machine had been fitted to the timber floor, and by way of reinforcement / security, four fence posts had been attached to the joists below the machine and concreted into the cellar floor. How effective this was i dont know!

 

[Bob.]

They're braver than me!

Unfortunately lack of foresight on my part but the floor was laid a couple of years ago and to get that section of floor up would involve taking up all the boards in the room - at least without cutting into the boards. I'm comfortable with the weight distributed between 2 walls and the floor but wanted to sanity check my thinking. If the advice was don't be daft or you need to get a structural engineer I would've gone that route but if the general consensus is the weight will be reduced to manageable levels across the 3 points than I'll give it try.