Hello, i'm building a new garage and am needing to put reinforced steel into the floor, as i haven't done this before, i was just wondering what you lay the steel onto, i've been told laying it onto bricks or blocks on the polythene is a way of doing it, has anyone any ideas or suggestions as to what to do in this situation. Many thanks Mr Hather
I just lay it on the polythene with a few loops of string through the mesh. Pour the concrete and get a rough level. Then just raise the mesh to the height I want, by pulling up on the loops. Then cut the loops, pull out the string and do the final level off.
My architect told me the mesh should be near the top and the best way was to pour the concrete and then put the mesh on and tamp it into the surface. I've often wondered about the logic of putting reinforcement at the top or bottom of concrete and have not been able to come to a conclusion.
Rob Graham
THE Reason reinforcement is at the top or the bottom.Depends on wether the ground is soft or hard.THINK of it like this A LINTEL ABOVE A DOOR must resist forces pushing DOWNWARD THEREFORE THE STEEL GOES TO THE TOP. IF the concrete has to resist SAGGING THE STEEL GOES TO THE BOTTOM eg SOFT SOIL/CLAY/SAND. SIMPLE AS THAT.
THERE ARE SPACERS AVAILABLE.which are shaped like THE ROOK IN A CHESS SET. Of varying size/heights,QUATER BAT BRICKS have been used for centuries so they would do as well.
I suggest that the lintel has to resist sagging and so the steel should be at the bottom, not the top.
The problem I have with this logic is that if you are above soft soil, the edge of the concrete may have less support than the middle (say) and therefore tend to break off. This would be solved by mesh at the top - the opposite of what you are suggesting. The 'lintel' analogy is not really adequate because with a lintel the ends are firmly supported. With a concrete raft the edges are not necessarily supported to that extent, and the support may vary across the width/length. One tends to view the problem only partially, because people might say 'the raft has to resist forces pushing downwards (as you said re the lintel) But are the forces pushing the middle down or the ends?
Rob
RE/ CONCRETE FLOORS, YOU WERE RIGHT ROB. Got me confused there,the specs state that in poor ground sand/soft soil/soft clay.The edges of the RAFT should exceed the middle x3 so a 220mm or 9 inch wall the sides edges need to be 600 mm thick to a width of 600mm in. The reinforcement bars do go to the bottom in tension ie lintel,The steel to the top for compression, GOT ME GOING THERE ROB CONFUSING, HODGES BOOK OF BRICKWORK gave me the answers.
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