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Joists bearing tank weight

S

sWozzAres

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Joined
30 Jun 2010
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231
Location
UK
I have a 180l tank but for a few years now, I've really wanted to upgrade to something like 350l.

The problem I have is that my living room is on the middle floor of a 3 story house, so my tank sits on floorboards that are supported by joists. I am worried that the tank will fall through the floor! I've had many failed attempts over the years to find out if my joists can support this weight.

The calculation seems easy enough...

if 1 litre = 1 kilogram then my 180l tank is 28 stone, which is just over 2 of me!
therefore the 350l tank would weigh around the same as 4 of me!!

Now if 4 of me went and sat down in the corner of the room, I wouldn't expect the floor to collapse, but long term I have no idea what, if any effect this could have on the joists, especially since the tank is near the wall so I wouldn't expect an even balance of load across the joists. I would expect there are building regulations that specify the maximum load of joists, but I've never been able to find these.

My questions are these...

1. Is the calculation correct
2. Do you know what the building regulations say in terms of load
3. Has anyone else had a 350l+ tank on joists with no problems
4. Has anyone actually had a tank fall through the floor and if so, what size was it

Any help much appreciated... :)
 
This is a common worry and it does depend on your house, joist sizes, condition of the wood. You want to place a tank in the stongest area possible.

Usually this will be placing the tank along the length of a bearing wall and where it can sit over as many joists as possible.

Always a good idea to consult a builder/construction engineer. I did for my 1600 litre, but my situation is different to yours. My tank is on ground floor, on doubled up joists and ontop of bearing walls that used to divide the room.

350 litre tank is a possibility, you just need to do some homework for peace of mind and preferably get some more professional advice.

Also your tank would not simply fall through the floor (well very unlikely) you would get warning signs first like sagging floor, doors not closing properly, cracks in walls...

It is hard to find information on the net, there is general stuff which mentions some of the things i have and then goes into more detail.
 
Hi sWozzAres

I just spoke to my fiance who is a Building Services engineer. It is his job to take an architects drawing and add in things like powered ventilation, domestic services, above ground waste and electrical systems. All these things have to be in line with building regs. He said that he doesn't really work on the joists and things so his knowledge of building regs in this area isn't great. He thinks it may be part e which covers things like walls. You may be able to access the actual regs somewhere, have a google.
In his purely personal opinion he said that the best place to position a tank would be spanning as many joists as possible and as close to the wall as possible. This is because of bending energy, have a think about levers and see-saws, its much easier to lever something with a longer leaver. Also next to a load bearing wall would be best. Apart from that he thought 350 litres would be perfectly fine :thumbup:
 
The one real important factor is, not just to span the weight, which is correct, but put a board underneath the thing...inch ply maybe.

Imagine two feet sitting just on floor boards and nothing else....you might not be sure if your on ceiling joists or not.
 
Mark Evans said:
The one real important factor is, not just to span the weight, which is correct, but put a board underneath the thing...inch ply maybe.

Imagine two feet sitting just on floor boards and nothing else....you might not be sure if your on ceiling joists or not.
Click to expand...


Oh yes, very true I forgot to mention that. I use 18mm marine ply under my tanks, helps distribute the weight.
 
From what I can make out there are two types of loads taken into account with floor joists, the DEAD load, which involves the weight of the materials that forms the make up of the floor being the timber, floor boards, plasterboards and skim. Then you have your Imposed load which is the amount of load you can impose on the floor by putting weight on it.

These maybe old regs I'm looking at but the dead load is not to exceed 0.5 kilo Newtons per m2 and the imposed load is not to exceed 1.5 Kilo Newtons per m2. That all depends on the make up of the floor and whether or not the underneath wall is definitely load bearing.

Here are some tables of floor make ups.

Spacing (distance apart) of joists.
400mm 450mm 600mm
Size of joist
38 x 97 mm 1.72 m 1.56 m 1.21 m
38 x 122 mm 2.37 m 2.22 m 1.76 m
38 x 140 mm 2.72 m 2.59 m 2.17 m
38 x 147 mm 2.85 m 2.71 m 2.33 m
38 x 170 mm 3.28 m 3.1 m 2.69 m
38 x 184 mm 3.53 m 3.33 m 2.9 m
38 x 195 mm 3.72 m 3.52 m 3.06 m
38 x 220 mm 4.16 m 3.93 m 3.42 m
38 x 235 mm 4.43 m 4.18 m 3.64 m

47 x 97 mm 1.92 m 1.82 m 1.46 m
47 x 122 mm 2.55 m 2.45 m 2.09 m
47 x 147 mm 3.06 m 2.95 m 2.61 m
47 x 170 mm 3.53 m 3.4 m 2.99 m
47 x 195 mm 4.04 m 3.89 m 3.39 m
47 x 220 mm 4.55 m 4.35 m 3.79 m

50 x 97 mm 1.98 m 1.87 m 1.54 m
50 x 122 mm 2.6 m 2.5 m 2.19 m
50 x 147 mm 3.13 m 3.01 m 2.69 m
50 x 170 mm 3.61 m 3.47 m 3.08 m
50 x 195 mm 4.13 m 3.97 m 3.5 m
50 x 220 mm 4.64 m 4.47 m 3.91 m

63 x 97 mm 2.19 m 2.08 m 1.82 m
63 x 122 mm 2.81 m 2.7 m 2.45 m
63 x 147 mm 3.37 m 3.24 m 2.95 m
63 x 170 mm 3.89 m 3.74 m 3.4 m
63 x 195 mm 4.44 m 4.28 m 3.9 m
63 x 220 mm 4.91 m 4.77 m 4.37 m

75 x 122 mm 2.97 m 2.86 m 2.6 m
75 x 147 mm 3.56 m 3.43 m 3.13 m
75 x 170 mm 4.11 m 3.96 m 3.61 m
75 x 195 mm 4.68 m 4.52 m 4.13 m
75 x 220 mm 5.11 m 4.97 m 4.64 m

If your house is old it may not be up to these regulations. So for example a 75mm by 122mm joist spaced at 400mm apart would achieve a imposed load of 1.5 knm2 when spanned across no more than 2.97 metres I would be guessing if I was to say halving the length would double the weight it could take but it is a starting point. I am a suspended ceiling contractor so floors aren't really my thing but I apply the same principles to a ceiling where it has to support heavy loads as well as the ceiling itself but my load is going in the opposite direction :) Now you need to convert the Kilo Newton metre squared into the weight over the m2 you have worked out for the tank but maths isn't my strong point :oops:

I deal with a few architects depts so will try and elaborate more.
 
Found this...
Quantity Reference Unit is equal to Conversion Factor Unit
1.5 kilonewton meter = 1.5 kilonewton meter
1.5 = 1500 newton meter
1.5 = 150000 newton centimeter
1.5 = 1500000 newton millimeter
1.5 = 150000000 dyne meter
1.5 = 15000000000 dyne centimeter
1.5 = 150000000000 dyne millimeter
1.5 = 152.957431947 kilogram force meter
1.5 = 15295.7431947 kilogram force centimeter
1.5 = 152957.431947 kilogram force millimeter
1.5 = 152957.431947 gram force meter
1.5 = 15295743.1947 gram force centimeter
1.5 = 152957431.947 gram force millimeter
1.5 = 17701.491117 ounce force foot
1.5 = 212417.893404 ounce force inch
1.5 kilonewton meter = 1106.34318175 pound force foot
1.5 = 13276.1181811 pound force inch

Is that saying 153 kilogram of force per m2 or other words 153kg of weight per m2 of area? Possibly
 
Not sure why I have my teeth into this :D but here goes. By my estimate of a 350ltr standard tank probably being somewhere in the region of a 4 foot by 2 foot that would mean exerting a force on the floor boards of 350kgm over an area of 0.84m2.

Sooo carry the 5 drop the 2 :crazy: that would mean the equivalent putting 208.3kg on 0.5 m2, if our floor in good condition and built to regs can carry 153 kg per per m2 then that would mean in this instance we are putting 416kg per m2 which roughly translates into not a good idea.

Or I could have all this wrong :D Just to add to that I'm not sure about the timespan involved but as the tank will in effect be a permanent fixture it may come under DEAD force in which case it's definitely not good. Granted these figures are probably the minimum allowed and tested too figures and the actual load it can take will be far higher.
 
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