Boise Concrete Contractors: Repair, Driveways, Patios & Foundations

Surface damage and structural damage look similar from a distance and need completely different answers. A slab whose top layer has flaked, pitted or worn away, but which is still flat, stable and un-cracked through its depth, is a resurfacing candidate. A slab that is moving, sunken or cracked through is not, and putting an overlay on it hides the problem for a season.

The usual cause of surface loss here is freeze-thaw combined with de-icing salt on concrete that was not air-entrained, or that was sealed before it had cured. Water gets into the surface pores, freezes, expands and lifts the top layer off. That mechanism keeps running every winter, so a repair that does not address exposure and sealing tends to be a repeat visit.

Resurfacing bonds a new wearing layer to the existing slab. It only works if the old slab is properly prepared first — ground down so the new layer has something to bite into, instead of sitting on dust. Poor surface preparation is a common cause of overlay failure. The existing slab has to be properly assessed and prepared before anything is bonded to it.

Your driveway works harder than any other concrete on the property. It carries vehicle loads daily, it takes the full freeze-thaw cycle without the shelter a patio gets from the house, and it is usually the first thing anyone sees. Those three demands pull in different directions, and a driveway that was poured to the thickness of a patio shows it within a few winters.

What decides the outcome is mostly invisible once the pour is done. Base preparation, compaction and drainage do more for slab life than anything in the mix. Much of Boise sits on Boise River alluvium — sand and gravel that carries load well and drains freely. The Bench and the Foothills are different ground, capped with windblown silt that behaves nothing like the gravel below it, so what worked on one side of town is not automatically right on the other.

Reinforcement, joint layout and mix strength then handle the loads and the movement. Control joints are cut so the slab cracks where it was planned to rather than across the middle, thickness is set for what actually parks on it, and the mix is specified with air entrainment — millions of tiny air bubbles that give freezing water somewhere to expand into as it turns to ice. It is an important part of freeze-thaw-resistant concrete, though durability also depends on the mix design, the water-cement ratio, curing, finishing, drainage and how exposed the slab is.

Many sunken slabs are still structurally sound and are candidates for lifting rather than replacement. What has usually moved is underneath: base material that settled, fill that compressed under the weight, or soil washed out by water that found a path along the slab edge. Which of those it is, and what condition the slab itself is in, both get established before anything is lifted — because the answer decides whether lifting is the right call at all.

Lifting works by injecting material through small holes drilled in the slab, filling the void beneath and raising the concrete back to grade under controlled pressure. Polyurethane foam and cementitious slurry both do it, with different weights, cure times and costs. The slab goes back into service quickly and the cost sits well below removal and replacement.

What decides whether it is the right answer is the state of the concrete and the reason for the drop. A slab that is badly broken up will not lift as one piece, and a void caused by running water will simply reopen unless the water is dealt with at the same time. Both get established before anything is injected rather than discovered halfway through.

A foundation does two jobs at once: it spreads the weight of the building over enough ground to carry it, and it holds that building at a stable level while the soil around it freezes, thaws, drains and dries. Everything above depends on it, and it is the one element of a building that cannot be economically corrected later. That is why it is worth getting the ground investigation and the detailing right before any concrete is ordered.

Ground in the Treasure Valley is not uniform, and that is the single most useful thing to know before designing a foundation here. The valley floor is largely Boise River alluvium — sand and gravel that carries load well and drains freely. The Bench and the Foothills are capped with loess, a windblown silt that is competent while dry and can lose strength and settle when it gets thoroughly wetted. Which of those a site sits on changes the answer, and the growth of the last two decades means a great many lots are also on engineered fill.

Foundation type follows from the building and the site rather than preference. A full basement, a crawl space stem wall, a frost-protected slab and a single-pour slab all solve the same problem differently, and the right one depends on the ground, the grade, what the space is for and what the building above needs from it.