Install a foundation later


Especially with older existing buildings, the owner's question quite frequently comes up with a retrospective installation of a foundation. That can have different reasons. What should be noted, if you want to install a foundation later, you can read here.

Subsequent installation of foundations in buildings: Determine conditions

So much is already written in advance: we can not offer you here a blanket solution to incorporate a foundation in a existing building subsequently. The problem starts with seemingly quite simple points:

  • Age (year of construction or construction) of the building
  • Type of foundation
  • Reason for the subsequent foundation
  • Completely subsequent foundation or foundation extension

Decisive which foundation exists or does not exist

Although often regionally defined, construction time and type of foundation are closely related. In buildings from the first half of the 20th century or even older, a natural stone foundation can be present as well as no foundation. The natural stone foundation is usually made of loose natural stones.

What to install later as foundation: base plate or foundation

It plays a role, what you call foundation. Because many homeowners mean a possible floor slab, which should then include the floor plan of the building or the individual rooms. Here it should be said that it can lead to errors that come through the resulting burden, the natural stone foundation under pressure and literally break out or walk individual stones. The statics of the building is then endangered.

Why install a foundation at a later date?

With that we would come to the reasons why a foundation should be retrofitted at all. One of the most common reasons is the attempt to dry a wet building, to get a solid base for a cladding (thermal insulation system, clinker, etc.) or already existing movements (settlement cracks) of the building.

The widening of existing foundations (strip foundations)

With a natural stone foundation you already know the problem. With strip foundations, it is only possible with great effort to widen them. For this purpose, ring beams are made of concrete and connected with tension anchors with the old foundation and clamped accordingly massive. But this can also affect the statics.

The undertaking of existing foundations

The more commonly used technique is then the endeavor of an existing foundation. A foundation is laid under the existing foundation. But here, too, the statics must be checked accordingly. This leads to the point that it must first be cleared around the building to see how the structure actually is.

Hydrogeological ground survey in front of the foundation

In addition, a hydrogeological soil survey should be compulsory. After all, the new foundation should finally be safely established again. In addition, it is often necessary, even in younger existing buildings, to check the conditions before retrofitting a foundation.

Common reasons for thinking about a subsequent foundation

The changed consumption behavior of drinking water alone has led to a significant increase in groundwater levels in many regions. Once properly prepared soil surveys are thus obsolete. And then not infrequently also the foundation of the foundations, once made.

Tips & Tricks

A particular challenge is when the building lowers (even partially) or risers are seen. Under such circumstances, it may be advisable to raise the existing foundation. There are also techniques (injections) that can be done instead of installing a new foundation.

Product Image: Lana Kray / Shutterstock


Video Board: How to Build and setup a Concrete Foundation for Garages, Houses, Room additions, Etc Part 1