I just thought I'd add a comment here.  I have a cottage built over 100 years ago on a row of bluestones instead of footings, on very deep highly reactive clay soil.  I think it's pretty good that's it's survived at all, but what with alternating water from leaking pipes and years of drought, then above average rain, and no provision for stormwater runoff, the cracks got bigger and bigger, both inside and out, as the soil moisture varied.  The engineer I consulted recommended site management to get the stormwater away from the house, and he also recommended urethane injection over conventional underpinning, as it would lift the house over a wider area, thus spreading the stresses.

I got quotes from both Uretek and Urathane Solutions, and had no hesitation in choosing Urathane Solutions.  The Uretek quote was a price range scribbled on the back of a business card after a brief look.  The Urathane Solutions quote was fixed price, with, as others have stated, any extra costs to be borne by the contractor.  In my case the cracks worsened between the quote and the suitable season to do the work, and there was indeed another 2 metres of injection done, at no extra cost.  Urathane Solutions also provided written explanations of causes and solutions to the problem.

While the job was being done, we got  comments from neighbours, 3 of whom had had conventional underpinning done  and still had problems.  I also had a chat with a passing engineer who had seen a Uretek sudden injection being done which had lifted the house too much, and caused the urethane to burst out between paving etc.  Mine was a much slower job, over about 2 and a half days, so that progress could be measured.  The cracks did not close completely…no-one says they will, but there is a visible difference, and hopefully when the house has settled and I have the cracks filled, it will last longer.

I am very happy with Urathane Solutions.