A living room under an exposed timber roof

Filler slabs: less concrete,same strength

A technique with a long Indian lineage that solves two problems at once — and a note on where it does not work.

Tall storage against one wall with the roof running over it
Where the structure is left as the finish, every line has to be right before it is built — nothing is covered afterwards.

In the middle of a floor slab, the concrete near the neutral axis is doing very little structurally. Replace some of it with hollow clay modules and you remove weight without removing strength.

Less concrete means less cement, a lighter slab, smaller beams, and smaller columns and footings all the way down. The saving compounds.

The second benefit is architectural. What you are left with underneath is a coffered ceiling in fired clay that needs no false ceiling, no paint and no maintenance. The structure is the finish.

It is not a universal answer. Filler slabs suit moderate spans and simple grids. They are slower to set out, they demand a contractor who will hold the module line, and they are unforgiving of late changes to service routes. If the drawings are not resolved before shuttering, do not use them.

neutral axisCOMPRESSION — concrete works hereTENSION — steel works hereHollow clay modules replace concrete doing little workRESULT — coffered soffit, no false ceiling
Clay modules sit where the concrete was doing least. Steel still carries the tension; the soffit below needs no ceiling.

What a filler slab changes

  • The middle of the slabClay modules go where the concrete was carrying almost nothing.
  • The bottom of the slabSteel still does all the pulling. Strength is unchanged.
  • What you saveLess concrete, less weight, less cement.
  • What you seeA patterned soffit. No false ceiling needed to hide it.
Related

Written by the studio. If you would like to discuss any of this against a specific site, get in touch.

Call the studio WhatsApp