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Transforming Small Spaces to a Full Foundation

Some homeowners with two small room spaces or an abandoned cistern would want to transform these spaces into a full foundation. However, they may be turned off by high cost estimates quoted by some builders. Before you go ahead and build a new room, let us get a more honest price estimate based on current city rates.

Cost of Turning a Crawl Space to a Full Foundation

Just how much will it cost to turn a tight room into a bigger and more usable area? If we consider the work to be done in connecting two rooms and materials required less the overhead and profit costs, the total would come to around $3,660. This already includes the following:

  • extra excavation (if it is in the basement)
  • foundation height
  • concrete floor
  • waterproofing
  • the task of cutting an opening into an old basement if needed.

In summary, you would only spend an additional $8.50 per square foot for a full foundation!

Cost of Building a New Basement

A new room would cost you nearly $45,000, which would translate to around $100 per square foot. Compare this to the above costs and we need not say more about which is more practical!

Converting a Cistern

If you have an abandoned cistern, then you can also turn this into a full foundation. All you need to do is empty the cistern, then contact a special contractor to hack an opening from the basement to the cistern. This would cost you below $400


Once your small space has been converted, you need to have it waterproofed. Ordinary asphalt should not be used as this will not close up cracks in your foundation. Instead, you can choose among modified asphalt with flexible compounds, liquid rubber compound or special panels with expansive clay. Hire a building company to do this for you.

Ask yourself these questions – do you need the additional usable space that a full foundation would give? Would this be a worthwhile investment in the long run? If your answer is yes, then it is time to turn that crawl space into something bigger.

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