Rebar spacers and tubes

About this section: Rebar spacers and tubes

Rebar spacers are responsible for the concrete cover, that is, the distance from the rebar to the surface of the structure. If the cover is less than the design value, the rebar rusts and the concrete spalls after a few years; if it is more, the structure loses load capacity. A plastic spacer costs next to nothing, while the offcuts of rebar and stones still used on many sites do not do the job.

Each case has its own type. A star spacer is fitted on a vertical bar in columns, walls and beams; the number in the name is the cover thickness and the second value the rebar diameter. A chair spacer goes under the bottom mesh of slabs and foundations and gives several heights at once, depending on which side it is placed. Wide-base spacers are needed on film waterproofing and soft ground, so as not to punch through the film. The T series are reinforced supports for the heavy cages of foundation slabs, and K-type spacers hold large diameters.

Consumption is worked out from the area and the type of structure: for a slab at least 4 chairs per square metre (the design sets the spacing), for a column 4 stars per running metre of bar around the perimeter. The 25 mm tubes and cones close the channel of the formwork tie rod, so that after stripping the wall keeps a clean mark and the rod comes out clean.

Sold in packs of 200 to 1000 pieces, the price per piece is VAT included; the 25 mm tubes for tie rods are sold by the metre. For sites with a large volume of monolithic work, the manager prepares a specification from the design cover thicknesses.