b'THE OFFICIAL NFBA MAGAZINEIMPORTANT CONSTRUCTION PRACTICES FOR QUALITY CONCRETE SLAB FLOORSSlab-on-grade floors are a prominent feature of most post-frame buildings. To obtain a quality and durable slab-on-grade floor, the slab must be both RESEARCH & TECHNOLOGYdesigned and constructed properly.Joseph M. Zulovich, Ph.D., P.E.P roper design was presented by Feldmann andcompacted), and keeps workers out of the mud. Schambach (2016).Proper construction isAddingthethicknessofthesubbaseand addressed in this article and includes properconcretefloortothesubgradeelevation site preparation, quality concrete, and carefulestablishes the final building floor elevation.concrete placement and curing.Also discussed are impacts of building fabrication sequence andConstruction Sequencingweather conditions on slab-on-grade construction. Castingtheslabduringtheconstruction processlargelydependsonthedetailsof Site Preparation thepost-framebuildingandconcretefloor.Site preparation for slab-on-grade constructionThe slab is always cast first where posts are to be typically consists of removal of topsoil and othermounted atop the slab or attached to a wall resting undesirable soils near the surface, grading ofon the slab.In buildings featuring embedded posts, the remaining native soil (a.k.a., subgrating),the construction sequence often hinges on whether and placement and compaction of a subbase.or not the posts are continuous.Continuous Verywetandfrozensoilconditionswillposts are those with the embedded and above generally delay these site preparation activities.ground sections delivered as one piece to the The extent to which existing soil should be removedbuilding site.Non-continuous posts have separate depends on soil expansive characteristics (i.e.,embedded and above ground portions.Many non-the change in soil volume with a change in soilcontinuous posts are comprised of an embedded moisture content) and the frost susceptibility ofconcrete pier attached above grade to a wood post.the soil.The extent to which existing soils couldFor post-frame buildings using non-continuous be problematic may require on-site soil testing. posts, only the embedded portions of the posts need The subbase should be constructed using a clean,to be placed prior to slab casting.Since most post-graded granular material since such a materialframe building piers only extend a foot or so above minimizes wicking of water upward from thethe subbase, interference of piers with concrete soil subgrade (i.e., it serves as a capillary break),pumping equipment and other slab placement provides drainage and frost protection, providesequipment is a non-issue.Once the concrete floor is goodstrengthandsupporttotheoverlyingadequately cured, the remainder of the post-frame slab,preventssettlement(whenproperlybuilding can be completed.The advantage of this 14 / FRAME BUILDER -OCT2020'