When Foundation Soils Are Weak, Chemical Underpinning Can Fix the Problem

When Foundation Soils Are Weak, Chemical Underpinning Can Fix the Problem


If any structure’s foundation soil is weak and cannot support its weight, most construction companies can inject this soil beneath its footing to increase its load-bearing capacity. Normally known as chemical underpinning or compaction grouting, the system uses a high strength polyurethane resin to develop solid underpins or a continuous section that will transfer the weight on down to a foundation that is more stable. Steel rods also can be embedded into the consolidated soil to provide resistance that is effective to uplift and movement. The system should be considered when:

  • Foundation soils are too weak to support existing structure and imposed load – if the soils foundation has already sunk, chemical underpinning can be used together with slab jacking or void filling to provide a repair that is total;
  • Foundation soil is unstable and slipping downhill;
  • Foundation soils are subject to vibration from construction processes, heavy plant, traffic, or seismic activity.

Soils water reactive

Clay soils that are water reactive, expand with massive force as the moisture content increases and then shrinks as they start to dry. This damage overlying structures, moving them up and down.

Problems this causes

The fallout from this is sticky doors, corners that rotate out, walls crack; concrete surfaces when uneven can cause veranda columns to peel away from buildings.

Glass in building or home

In certain cases, glass shower screens and glass windows can shatter due to pressure caused by a shifting structure.

What is the cost

So, the problems arising from a foundation that is not on firm soils can be fixed with underpinning. That should be good news, but unfortunately, with houses, home insurance will not cover the cost. Whatever the cost, this job must be done if you don’t want any further problems.

How to get a quote

Before you can get the cost of underpinning, you will need to find the extent of the problem and what must be done. People who can do this for you include:

  • Concrete or other trade professional specializing in underpinning can give a quote;
  • A structural engineer also can inspect your home and give you an engineer’s report.

Make sure you have your quote from a firm that knows what they are doing, so that you will not be spending extra money to get information for the quote.


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