Foundation, Concrete and Earthquake Engineering

How to do underpinning in foundations

Underpinning is a method used to increase the foundation depth. This may be done in case a developer wants to add more storeys to a building. Also the foundation could be damaged by tree roots and thus this method used for correction. The adjacent construction may have foundations lower than the existing thus requiring to be lowered. If basements are constructed very near an existing building, the foundation may need to be changed. The reason is for stability of the existing house. Cracks may appear in a building up to the base thus needing a foundation remedy.

The underpinning in foundations may be undertaken and but supervised by an engineer. This works should follow instructions keenly for safety. Before any commencement, of work the area of operation should be hoarded. The works take from excavation to finishes approximately a month to complete.

Underpinning operation increasing bearing area of foundation The area to work on is measured and mapped out. The work should commence from the corners working inwards. This is done on load bearing walls only.

Foundations without any load bearing walls are exempted. The defects on these walls can be corrected using most simple methods.
The underpinning in foundations starts with excavations. This should be done under a strip footing. A length of one meter, a width of half a meter and depth of half a meter pit is dug. This is done in stages of two meters. This is distance between the pits. After the excavations, mass concrete is added to the cavity. Mixes are one part cement, three parts sand and six parts aggregates. Concrete is made to a good consistence and is poured into the cavity. Use form work on the edges. Use a rod bar ensuring that the cavity under the existing foundation is filled up.
Increasing Basement Height by Lowering Foundation
After the underpinning concrete is placed in the cavity, its allowed to set for two days. The operation is repeated for the next bay. This continues until the required foundation is complete. Ensure that the concrete is cured thoroughly before loading it. The next thing is to break off the projecting foundation. Cut the concrete flush with the mass concrete surface. after this is completed for all the bays, soil is then back filled and compacted thoroughly. Watering with a hose is done for consolidation of the soil. This is done upon completion of the work.


  1. Excellent and brief explanation on reenforcing the structural integrity of a home. I've seen an entire building be dug up underneath ( a new basement was created) and the whole house was on stilts. Incredible.

    Ansel Marvin | Earthworm Reblocking and Underpinning

    1. A house in my neighborhood had to get this done just a few months ago. It was amazing the whole process that it goes through. It is hard to believe they can do that without ruining anything. Before that happened I didn't even know what underpinning was.

      Alena |

  2. I really appreciate this post. It does a great job explaining how foundation underpinning works. After seeing how complicated it is, I think I'm going to leave it to the pros. Thanks!

    Rosie |

  3. This is such a interesting job to go under a house and fix the underpinning! I bet you guys see some weird stuff down under a house, right? This article was helpful to understand the process of underpinning!
    Celine |

  4. Thanks for posting this. I've been trying to find out how to do it. I've wanted to learn about building and construction for a while now. I would like to eventually try doing this on my own.
    Gary Puntman |

  5. foundation underpinning looks so complex. I really don't know if I would make that a Saturday project for many reasons. I think though it would be a good idea to look into this a little more. It would definitely help keep my house stable and also make sure the foundation doesn't break.

    Zach |

  6. Foundations are something that I would hate to have a problem with on my house. It is a lot of work and it is something that really should be done by professionals. There are a number of problems I would take over having something go wrong with my foundation. Though it really isn't a choice in most cases.

  7. I didn't even understand what underpinning was before reading this blog. My basement floor is starting to crack, which doesn't bode well for the foundation. If there's any way to repair things before they get worse, I'm all for it.

  8. Hello,

    This is an amazing piece of writing. You have explained the complex process of underpinning effortlessly. After reading your post, many homeowners will realize that instead of buying a new home, underpinning foundation is a great way of increasing the space in basement floor as well as for increasing the strength of the concrete structure.

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  10. Very informative post, explains complete procedure of basement underpinning, thank you for sharing.

  11. Good one you explain. all building and civil related work to must use for the pre engineering process is very well done to introduce. its call us for PEP. Majorly access material is aluminium scaffolding for access and tools used for core work. Thanks for the opportunity. and Thanks Admin.

  12. Great example of underpinning. However i might add that different cased vary , and all works should be engineered always. To many people get away with illegal activites in Australian underpinning industry.

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