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  1. #1

    Garage Suspended Floor Strength

    I have a 750Gal EZPond on order due for delivery next week. I am planning on putting this in the back of my garage. It has suddenly dawned on me that the floor, whilst concrete, is of suspended construction (house built in 2008). I have just worked out that 750G of water weighs 3.4 tonnes.

    So, will the floor collapse with this weight on it or not?! Having already had a flood in the main house, I could do without another in the garage, not to say the stress of loosing the fish!

    I guess I could put some large sheets of thick ply down to spread the load to help, or is it not necessary?

    Any thoughts?

    Thanks
    Barry



  2. #2
    Member Rank = Tosai Dudley's Avatar
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    Hi Barry
    An engineer is probably going to be required to some calculations for you, and he will want to know exactly how the floor is constructed, not just know its beam and block. Beam and block flooring is not standard, it is designed specifically for the loading it is expecting to take and the span. No amount of ply or load spreading material will help if the overall loading is exceeded. The typical I beam can be laid in single rows set at concrete block width centres, or they can be doubled up to take more loading, ie two beams side by side, but that is usually only necessary on wider spans. I built my house with beam and block and they are all singles, but a barn conversion being carried out now on my farm has double beams. But that said, they are still only designed with domestic loading in mind.
    But you say it is a garage, and therefore you may be ok. But you really need to get details off the original building regs application to find out.

    Its not flooding you need worry about, because if the beams crack the floor will simply collapse on its own weight, and anything on it will fall through.

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    If the garage floor is designed to be able to take the weight of a large car then you may be ok. Hard to guarantee that though without seeing the original plans.

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    Senior Member Rank = Mature Champion andikoi's Avatar
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    Ive had a 500g qt sat on 18mm osb3 for 4 months inside my filter house which just has a timber frame floor and no damage whatsoever. Andi

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  8. #5
    I think I have the drawings somewhere, I had to get them 2 years ago after the basement flood because I wanted to move a wall. I will try to dig them out, I figured there wouldn't be a simple answer, but I was hoping loads of people were going to come back and say they had done the same with no issues

    It's a detached garage, probably just short of the width of a triple, more like 2.5. There's already a car in there and some racks with crap loaded up on them too....

    It didn't even cross my mind when I ordered the tank, but for some reason just popped in there when I got the reminder pop up for Monday's delivery! Doh.

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  10. #6
    Member Rank = Tosai Dudley's Avatar
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    I believe a domestic garage constructed with concrete beam and block is designed to take around 400kg per square meter. Thats based on a garage 2.8 x 5.5 x6m 15.4m2 so the total live loading could be 6 tonnes ish. An average car is about 1750kg and the weight of the car is distributed over a large area. You need to work out the footpint of the tank.

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  12. #7
    Footprint of the tank is 2.5m x 1.3m so 3.25 sq m

    so I think 3500 kg roughly for the pond, that’s more like 1000kg per square metre! Looks like I need to find those plans!

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  14. #8
    Extreme Koi Member Rank = Adult Champion pip895's Avatar
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    A car has all its weight distributed on effectively four relatively small pads. If you work out the weight/m2 under the weels it will be far higher than your pond. I would be very surprised if you have a problem.

    If you are worried though take your plans to a structural engineer.
    6000g unheated in ground koi pond
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    Bottom drain & Skimmer to Drum
    JBR boichamber->Blue eco 500 pump ->below surface return.
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  15. #9
    Member Rank = Tosai Dudley's Avatar
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    Quote Originally Posted by pip895 View Post
    A car has all its weight distributed on effectively four relatively small pads. If you work out the weight/m2 under the weels it will be far higher than your pond. I would be very surprised if you have a problem.

    If you are worried though take your plans to a structural engineer.
    Your referring to point loading here, and loading on a dense concrete floor is different to a soft surface. An example would be a girl marking a vinyl floor when wearing stiletto heals, where ordinary shoes would not.
    A suspended concrete floor can take a lot of point loading due to the density of the materials used in construction and the way each beam and block is tied into the adjacent beam and block with cement slurry. Theoretically one could put all of the 400kg per square mt onto 1 square mm and you wouldnít mark or dent the concrete, but put another 400kg on the next 1 sg mm and so on and the floor will soon fail. But you probably could do this with a floor thatís not suspended as the weight is transferred directly down. But you cannot on suspended floor because ALL the live load weight, and dead load weight, ie floor itself has to be born at the point the beams are supported at the ends, ie foundations.
    One thing in the OPs favour is if the garage is 2.5m wide and the tank is full width a lot of the weight will be at the ends and supported partially directly on the foundations.
    But as we both say, if he is concerned he should consult a structural engineer.


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    Extreme Koi Member Rank = Adult Champion pip895's Avatar
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    The point is that the front axle weight of a car could all be sitting on a single beam but the pond will be spread over several.

    Worth looking at the plans before siting it to make sure it is positioned to be as well supported as possible - its quite a large garage. Is it actually beam and block or reinforced concrete - our garage was described on the plans as a suspended floor but it was just the reinforcing that was supported. Under the concrete before fill was compacted hardcore. Possibly naively I would have no issues at all in putting 1 tone/m2 on it, but a beam and block floor with free air underneath might give me pause for thought and send me in the direction of a structural engineer.
    6000g unheated in ground koi pond
    +3000g lily/Anoxic pond attached
    28 koi (40 to 65cm)
    Bottom drain & Skimmer to Drum
    JBR boichamber->Blue eco 500 pump ->below surface return.
    Blue Eco 240 -> Large MB -> Waterfall -> Planted Anoxic pond (25 baskets)

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    Member Rank = Tosai Dudley's Avatar
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    Quote Originally Posted by pip895 View Post
    The point is that the front axle weight of a car could all be sitting on a single beam but the pond will be spread over several.

    Worth looking at the plans before siting it to make sure it is positioned to be as well supported as possible - its quite a large garage. Is it actually beam and block or reinforced concrete - our garage was described on the plans as a suspended floor but it was just the reinforcing that was supported. Under the concrete before fill was compacted hardcore. Possibly naively I would have no issues at all in putting 1 tone/m2 on it, but a beam and block floor with free air underneath might give me pause for thought and send me in the direction of a structural engineer.
    Hi again
    I donít want to get into an argument because we are both giving the same advice to the OP but our interpretation of suspended flooring differs.
    What you say about the front axle being supported on one beam is incorrect. You would be correct if it were a timber floor, but a single beam on a beam and concrete block floor if constructed correctly does not take all the weight that is placed on it.
    When I lay the beams we feel a lot of bounce and flex when standing/walking on that beam alone, then we lay the dense concrete blocks between the beams, but there is still flex and bounce on individual beams as it is not yet all tied in.
    We then run a grout of cement all over the floor, this grout slips down between all the blocks and beams virtually glues them together. On top of that goes the screed.
    The floor then has no bounce, itís virtually a concrete slab, the loadings are dissipated diagonally thorough the structure, unlike timber suspended floors.
    Therefore as I said before, the total loading for that floor could be placed in a small area, but exceed that, the entire floor could collapse.
    And the OP could identify if the floor it truly suspended and not a slab in that the suspended will or should have air vents around the DPC line of the external brickwork.


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  21. #12
    Extreme Koi Member Rank = Adult Champion pip895's Avatar
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    Im sure you are right Dudley I stand corrected - you clearly know much more than I do - my knowledge on this is very out of date in any case - when they put ours down the screed was separated from the beam and block by a dpm and insulation + we can feel some bounce when crossing some of the larger rooms.

    The, now converted, garage with the so called "suspended" reinforced floor feels very solid - no vented bricks under that one as you say, unlike the main house. It was definitely described on plan as a suspended floor though?? - I remember questioning it at the time - the reinforced slab is sitting on top of foundations including at least one foundation running across the garage. If the OP could site his pond over /close to foundations I guess that would help.
    6000g unheated in ground koi pond
    +3000g lily/Anoxic pond attached
    28 koi (40 to 65cm)
    Bottom drain & Skimmer to Drum
    JBR boichamber->Blue eco 500 pump ->below surface return.
    Blue Eco 240 -> Large MB -> Waterfall -> Planted Anoxic pond (25 baskets)

  22. #13
    Hi,

    i still havent found the drawings yet! I’ve ventured out tonight to have a look at where a recent new power feed was brought into the garage. There is a slab at least 4” thick, I can’t see any evidence of a suspended floor here, but the lighting isn’t good at night so I will take a look in the daylight. I’ve checked for air vents and there are 2, but only near to one corner of the garage where the oil boiler used to be and the pipes for that go into (and therefore under) the floor before they make their way across the drive and back to the house. Is it possible that just that corner of the garage has a suspended floor?

    i am planning on putting the QT against the corner of the garage so it would be near the walls / foundations, but at this point in time I was planning on putting it where the boiler used to be!

    i will investigate further tomorrow, but in the mean time, here’s a picture of where the new power supply enters the garage.
    Attached Images Attached Images
    Last edited by GadgetBazza; 04-11-2018 at 09:40 PM.

  23. #14
    Member Rank = Tosai Dudley's Avatar
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    That looks very much like a solid concrete floor. I would have expected to see a concrete beam running along the side of the wall in one direction or another. It could be that I am looking at a hole in a dense concrete block, but it looks more like solid concrete.
    And it also looks like hardcore at the bottom and if the concrete is sitting on the hardcore its a solid floor and you need not worry.
    I believe there should be a minimum of 150mm free air space under a suspended floor for air flow and I cannot see you have that, again pointing to solid concrete.
    Regarding the air vents, you are probably seeing vents to supply the oil boiler with air.
    I think you should sleep better tonight.
    Good luck with the delivery tomorrow. Steve.
    Last edited by Dudley; 04-11-2018 at 10:24 PM.

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  25. #15
    Member Rank = Tosai Dudley's Avatar
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    Barry, How did you get on, is the tank installed and filled?

  26. #16
    Quote Originally Posted by Dudley View Post
    Barry, How did you get on, is the tank installed and filled?
    Hi Steve,

    not yet, it was delivered on Monday as promised, but I've decided to play it safe and get to the council offices to check the plans. Reason being is that whilst that photo I posted (taken on the mid way down the right hand side of the garage) looks like it's on a hardcore base, the boiler pipes in the back left corner are floating below the floor (might be in ducting, I'm not sure). There are also two air vents on the left hand wall and two across the back wall, they are fitted on the 2nd course below the internal floor level.

    I'm hoping that there is a cavity in the footing across the back of the garage and the left hand side to allow for the multitude of mains cables (we have four consumer units, 3 of them in the house are fed from the main incoming supply in the garage) as well as the boiler pipework because the boiler was installed remotely from the house (presumably to keep the oil tank away from the property).

    So I want to make sure that the left hand half of the garage isn't suspended for example... The council responded to my email today and then called shortly after but I was on the phone, they've left a message to call back tomorrow, so I'm hoping they can pull the file soon and I can pop in and go through the drawings and take some pics. Better safe than sorry, I've just come out of a 2 year flood claim on the main property, I could do without destroying the garage!!!

    Will keep you posted though, I'm itching to get the tank up and running, as are the fish!

    Thanks
    Barry

  27. #17
    I meant to add, there is definitely a base underneath the 4" slab in that photo I took and no 6" cavity that you mention.

  28. #18
    Well, I've just had a call with building control and they have confirmed its a block and beam pre-cast floor in the garage. I've indicated what I want to put in there on the phone and they are doubtful it will be sufficient but depends on the manufacturers tables. Apparently there is a 300mm void and the spans are the full width of the garage!

    The are going to get me a copy of the floor diagram, hopefully the manufacturer details are on there and I can look into it a bit further, but it looks doubtful that I can put the tank in the garage in the short term at least....!

  29. #19
    Just got this drawing through, although I can't make much of it with regards to the floor....
    Attached Files Attached Files

  30. #20
    Extreme Koi Member Rank = Adult Champion pip895's Avatar
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    That's a standard suspended beam & block floor I'm afraid - there should be air bricks all round. It is always possible that the builder went off and did something completely different - it isn't entirely unknown.
    6000g unheated in ground koi pond
    +3000g lily/Anoxic pond attached
    28 koi (40 to 65cm)
    Bottom drain & Skimmer to Drum
    JBR boichamber->Blue eco 500 pump ->below surface return.
    Blue Eco 240 -> Large MB -> Waterfall -> Planted Anoxic pond (25 baskets)

 

 
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