Expert: Dan Griffin - 12/24/2008

Question
QUESTION: Hi Dan
     I have a large fish tank in my first floor flat. Its 6x2x2 ft and weighs around 2000 pounds I have it sitting on a piece of plywood 6x2 ft. Under this is 4 tiers of breeze blocks, only 2 high to keep the weight down. All of this sitting on a thick piece of plywood 8x3 ft to spread the weight. The tank is placed againt the outside wall of the flat. I have read many web sites on how much wooden floors can take, but cant find anything on how much concrete floors can withstand. Hope you can put my mind at rest.
         thankyou
         mark white

p.s The tank has already been in place for nearly a month now!

ANSWER: Mark, I appreciate your concern.  We have to make a few assumptions.  The concrete that was used was probably 3,000 psi (pounds per square inch) so we are not worried about crushing the concrete.  What we do need to worry about is the compaction of the soil under the slab. This is usually some form of compactable fill (sand, gravel, etc)  If there were a void or settlement of the fill, it would allow the slab to crack.  I don't see this as a large issue on the ground floor, especially since you have sitributed the load over  a larger area.  I wouldn't worry about coming home to fish and water all over the floor - sleep easy.

---------- FOLLOW-UP ----------

QUESTION: Hi Dan
     Sorry i didn't explain that very well. What i was trying to say is that i am above another flat so I'm not on the ground floor. So I'm more concerned about the tank causing a crack in the ceiling of the people who live downstairs. Like i said i've had no problems so far, and my dad has said any flat which has cookers, fridge/freezers, baths and central heating boilers etc, must have some kind of steel supports running though the concrete floor. Do you think this probably the correct assumption or should i remove the tank? I did speak to a builder and he said there are two types of supports used in upstairs concrete floors, but didn't say what they were! or how much upstairs concrete floors (flats) can take. sorry to be a pain! i do hope you can help.
         Thank you for your help
         MarkWhite

Answer
Mark, there are more than 2 ways to have a second floor concrete deck.  Core decks, reinforced concrete, composite decks (steel bar joist w/ coruform steel decking with concrete overlay.  As long as your aquarium is along the outside wall, it just won't matter.  I'm sure you are fine.