What Is Grouting
Updated
Grouting is injecting or pouring a genuinely flowable material — usually a cement-based or chemical grout — into cracks, voids, joints or soil specifically to fill them, seal against water, or strengthen the ground beneath or around a structure. It's a surprisingly broad term that ranges from the ordinary grout filling the gaps between your floor tiles all the way to pressure-injected ground improvement beneath a foundation, and confusing the different types can lead to specifying the wrong material for a given repair. This page sets out the types actually used and exactly where each belongs.
Fills voids, cracks & joints
What grout physically does
Cement-based or chemical
The two material families
Seal, fill or strengthen
The three underlying purposes
What grout actually is, and why it works where solid concrete can't
Grout is a genuinely fluid mix — typically cement combined with water (sometimes with added sand or chemical admixtures), or alternatively a chemical resin — deliberately made thin enough to flow readily into and completely fill a gap or void, and then set hard once in place. Because it actually flows rather than needing to be packed and compacted like ordinary concrete or mortar, grout reaches into narrow cracks, tight joints and irregular voids that conventional concrete simply cannot be worked into by hand or trowel.
Types of grouting compared
A relative ranking of how far and how fine the grout must flow to reach its target gap — not an engineering scale, since actual mix design depends on the specific application.
| Type | What it is | Where used |
|---|---|---|
| Cement grouting | Cement-water slurry, sometimes with added sand | Filling voids, cracks, gaps under base plates, honeycombed concrete |
| Non-shrink grout | A special formulated grout engineered not to shrink on setting | Machine bases, column base plates, precast concrete joints |
| Chemical grouting | Resin or polymer injected under pressure | Fine hairline cracks, water sealing, active leak stopping |
| Tile grouting | Fine cement or epoxy-based grout | The joints between laid floor and wall tiles |
| Soil / pressure grouting | Grout injected directly into the surrounding ground | Ground improvement, sealing seepage paths under foundations |
Where grouting is actually used on a real project
- Filling voids and honeycomb discovered in cast concrete, and specifically the gap left under machine and column base plates once they're set and levelled — non-shrink grout is essential here because any shrinkage would leave the base plate resting on an uneven, partially voided bed rather than a genuinely full, level contact surface.
- Sealing active cracks and leaks — cement or chemical grout injected directly under pressure into a crack to stop water ingress, used where the crack is too fine or too active (still moving/leaking) for a simple surface patch to reliably hold.
- Tile joints — the ordinary grout that fills the narrow gaps between tiles after laying, which both seals the joint against moisture and locks the tiles firmly in place (see the tile calculator for laying quantities).
- Ground improvement — injecting grout directly into soil beneath or around a foundation to fill natural voids, raise the soil's density, or seal off seepage paths that would otherwise threaten the foundation's stability.
Why surface preparation matters just as much as the grout itself
The surface or crack being grouted must be genuinely cleaned first — free of any residual laitance and loose material — before the grout is injected, since grout that flows into a void still contaminated with loose debris or a weak laitance layer will bond to that weak layer rather than to sound concrete underneath, undermining the entire repair regardless of how correctly the grouting itself was executed. For related crack context, see types of cracks in concrete, and for the sprayed-application alternative used on larger repair areas, see guniting and shotcrete.
Frequently asked questions
What is grouting? Grouting is injecting or pouring a flowable cement-based or chemical material into cracks, voids, joints or soil specifically to fill them, seal against water ingress, or strengthen the surrounding ground.
What are the types of grouting used in construction? Cement grouting, non-shrink grouting, chemical (resin) grouting, tile grouting and soil/pressure grouting are the common types, each engineered for a genuinely different purpose and required fluidity.
What is the difference between grouting and pointing? Grouting fills voids, cracks or joints with a flowable material that flows in on its own and then sets. Pointing is the finishing of mortar joints on an exposed masonry face, worked in by hand with a trowel — grout flows into a gap; pointing is manually shaped at the surface.
What is non-shrink grout specifically used for? Non-shrink grout is used under machine bases, column base plates and within precast concrete joints, where the grout must fill the gap completely without shrinking away afterward and leaving voids that would compromise the bearing contact.
What is tile grouting, and why is it needed? Tile grouting is filling the joints between laid floor or wall tiles with a fine cement or epoxy-based grout, which both seals the gaps against moisture ingress and locks the individual tiles firmly in place relative to each other.
CivilSite Editorial Team✓ Engineer reviewed
Written and reviewed by practising civil engineers with 10+ years of Indian residential construction experience.