Morning All, Generally i always find an answer on here but this is a bit specific so was hoping for some advice. I have tried to contact a few structural engineers to come and take a look but to no avail (guess it is too small a job for them to take time out?) Anyway we have purchased a rather large fish tank but live in a 1930's detached house and i am positive the ground floor will not like that kind of weight, the size of the tank and cabinet is 1440mm x 420mm and the weights from the manufacturers are; Cabinet: 51kg hood: 22kg tank: 74kg water volume 310lts: 310kg So all set up and running i can safely assume this will be pushing over 500kg I have attached a crude sketch of the room and layout to understand it better and where the tank will sit about 400mm from the outside wall (if anyone needs technical drawings to scale like this one do let me know...) There is a little hatch at the front of the house i have been able to take a look directly under where the tank will sit. All the walls are solid load bearing and a total room size of about 3.8m x 3.8m. joists are 100mm x 100mm (4x4) and spaced at 400mm (16") small for joists i know. the joists run from the outside wall to the wall between my front room and back room, in between this there is a sleeper wall, the sleeper wall is roughly 2m from the outside wall and then 1.7m to the wall between the rooms. So i am planning on putting another 3 joists between the outside wall and sleeper wall under where the tank sits then use structural ply under the tank instead of floorboards, is this a sound solution or not advisable? Sorry for the long post but appreciate any help
unfortunately not, on the outside wall it is a bay window and the dividing wall between the room is actually a double doorway knocked through so it will only be able to sit on the walls that the joists run parallel with
What’s underneath the floor? Is it bare earth or concrete? You could put something under the joists the tank will sit on. If you search the forum for “joist jacks”, I had a conversation with someone on here a while back and there will be images of a few of the products we used. If you’ve earth underneath you could use slabs or steel plate to spread the load. Another alternative is to shutter out the space below the tank and pour a concrete slab.
Joist jacks seam a good shout! Just earth in the crawl space so could just use some slabs to sit them on Quite a deep crawl space so would prefer that to a concrete slab i think
You could even just shore up with stacks of blocks as long as they’re stable. We had a big tank like yours previously and I was surprised how ‘flimsy’ the manufacturer’s supplied cabinet was! Some fish species will grow to fit the tank and we ended up with a couple of monsters!
Pop a concrete slab in and use timbers in to support. You don't need jacks: folding wedges will do fine.
Yeah it is a bit of a beast, thankfully we have a pond so if they get too big they can take there chances in there instead The reason i went for these Aquaoak is the cabinets are made of oak so are nice and solid, all the others i seen were pretty much 2x2 with some chipboard tacked on, didn't fancy that
So just straight timbers down onto a concrete slab? Just screw/ bolt these to the joists currently there? Instead of the joist jacks
If you are taking up te boards and fitting ply, I would suggest bring it out to the third joist which will spread the load a little more. Timbers to support each joist is a good idea, maybe put some 400 sq paving slabs down under each leg
Keeping things simple, assume you have 5 joists taking the load of 500kg, so that would be 100kg/joist. this load would be over 1.44m length of joist so this equates to 70 kg/m run of joist and for calculation purposes assume this load is acting over the complete span of the 2m joist i.e a total load of 140kg. Running the calcs show that for a C16 wood class deflection would be 3.7mm against allowable of 6.1mm and bending moment of 0.5knm against allowable of 1.1 knm, hence your proposals are safe (even more so strength wise if the existing wood or the wood you propose using is greater than C16)
Thanks for the advice guys, think i will double the 2 joists that are there (they are nearly 100 years old after all!) And stilts of some description down to slabs. I will bring the board out to the 3rd joist also, never thought of that but it makes sense as i have to pull the floorboards anyway so it is not any extra work really
Thanks severntrent i was planning on using c16 as it seams available and cheap enough, i think a combination of a few extra joists and "props" are the way to go. Despite everyone i speak to say just fill it, it will be fine i would rather go overkill and not worry about it
I often get asked about gun/ammunition safes - can get 250kg on 450x350mm, half the weight in quarter the length!. I know of one where there are 150x75 joists on 300 centres spanning around 1.5m.
Just doubling the joists would put you at the limit of allowable deflection and at approx 80% of allowable bending moment
Hi guys, stuff ordered for delivery i will update with the progress and hopefully a tank full of water! Thanks for the help all