Concrete Isolation-Joint Filler Takeoff
Pre-molded isolation-joint filler (usually 1/2 in fiber or foam) around a slab-on-grade where it abuts rigid elements so it can move independently: filler = 2 x (length + width) + columns x column-perimeter, strips = ceil(filler / strip length). A 40 x 30 ft slab around six 12 in columns is 164 LF (140 perimeter + 24 columns), 17 ten-foot strips; a 50 x 40 ft slab with no interior columns is 180 LF. This is distinct from the sawn CONTROL joints (concrete-sawcut-footage), which relieve shrinkage within the slab. The structural and slab-on-grade details (ACI 302 / ACI 360) govern where the isolation joints go and the filler type.
Formula and source
slab_perimeter_ft = 2 x (slab_length_ft + slab_width_ft); column_isolation_ft = round(num_columns) x column_perimeter_ft; filler_lf = slab_perimeter_ft + column_isolation_ft; strips = ceil(filler_lf / strip_length_ft).
ACI 302 (Guide for Concrete Floor and Slab Construction) and ACI 360 (Design of Slabs-on-Ground) isolation-joint practice, by name; the structural detail governs the joint locations.
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