Graphical Construction Glossary >> Concrete and Concreting. >> >> Bar Chairs
One would think that these items are just about as simple as you can get and they do not need any explanation at all. Not so, I have just done a really quick search on the web and found that one manufacturer has a photo of a bar chair similar to the one on the right that is being used to support two bars crossin each other.
That is not how these chairs work. The chairs have two different depths so that they provide you with two heights to choose from. The higher notches in the chair on the right may give you a 65mm concrete cover and the lower notches may give 50mm concrete cover.
bar chairs always sit under and support the bottom layer of bars.
If you need to use your chairs under the top layer to get the right cover, forget it! Buy the right size bar chairs because you run the risk of some of the bottom bars dropping under the weight of men and equipment during the pour, which will reduce the cover.
This applys to rebar and to mesh. If you use them to also try to locate the bars it is wrong.
This was a rough and ready system but it was a lot bette than holding the rebar up with broken bricks etc. that I have seen all too often.
The above photo shows a contiuos plastic strip of chairs. this is used when heavy steel loading would crush normal chairs.
the last word on rebar chairs. Better ten too many than one not enough!
If you didn't find exactly what you are looking for try this search tool that will search the site and the web.
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"When we build, let us think that we build for ever."John Ruskin 1819-1900
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