Foundation of an extension – How do I deal with that? Many people have the desire to enlarge their home. Expanding a conservatory is then a logical choice (if you have the space for it). With a kind of renovation you win a lot of square meters and plus the house is also worth more. A lot of attention is always paid to the implementation itself, but the foundation does not always get the attention it deserves. Because improperly thought out financing can cause damage to the construction. This can result in damage in the form of cracks, but also in subsidence of failure of a part of the structure. Unfortunately, this does not happen often. Good financing is therefore important. But how is it a what kind of. That is explained below.


There are two factors that play a great role by defining the foundation:

  1. The weight of the structure
  2. The composition of the substrate



Weight of the structure


The weight of the structure determines the type of financing for the extension. It is of course logical that as a construction light is the money deposit. But it is not always obvious what a bit of heavy construction is. Indeed, there is already a big difference between an extension made from timber-frame construction made from brick walls. A combination of heavy and light structural components in an extension, like a heavy glass front, is also combined with walls of timber frame construction. A calculation must be calculated on these taxes. A light construction means less financing and a huge construction.

Composition of the substrate

The composition of the subsoil is also very important for both the severity of the financing and the type of financing. In the Netherlands we can roughly divide the composition of the soil into two categories. The first category consists of soil that consists of sand packages. Sand is a strong material and this is often used for foundation. The second category consists of clay, peat and loess. These materials are seen as weak materials and are not suitable for direct foundation. This is because these materials lock in when loaded. For this type of substrate, therefore, a different form of foundation is required than the substrate consists of sand. A roughly introduced distinction is made between the following two types of foundations:

1. Foundation on steel
2. Foundation on piles

Foundation on steel

If the composition of the soil consists of only sand, a foundation can be applied to steel. As the name suggests, no steel is involved. A foundation on steel meant that the financing can be placed directly on the load-bearing sandy soil. The best way is to deposit a solution on the compacted sand package. However, I do not recommend choosing this option, especially if it concerns a deeper extension of a greenhouse of more than 2 meters. The condition of the Obstacles plays a very dominant role. The ground layers must run parallel to each other. If this is not the case, the chance of a skew due to uneven sagging is very high.

It is better to base the structure on foundation beams. Will become become becomes becomes ing ing ing ing ing ing ing ing ing ing ing ing ing ing ing ing ing ing ness ing ing. These foundation beams then bear directly on the load-bearing sand layers. This can be achieved.



Foundation on piles

If the composition of the soil consists of clay, peat and / or loess, a different type of foundation must be used. These types of soil are are to be used for the loads of the construction or the in build too. Poles, usually made of concrete, are then used to transfer the loads from the structure to the deeper, load-bearing sand layer. The foundation beams are then poured onto these piles, on which the construction of the extension can be built.


Expansion as a stand-alone construction

As a constructor I get the question of and why the expansion should be founded as a separate structure. The fact is that the ground still has to get used to the new weight of the construction of the extension. In this case, if the foundation of the extension is linked to the existing financing of the main building, the existing financing will be charged extra. This can cause cracking, also in the brickwork. The extent to which the foundation can set depends on the ground conditions. It is on the edge of local conditions to what extent an extension must be founded as a separate structure. My experience is that a connection to the existing foundation is only possible if the dimensions of the extension are very small.

Looking for advice?

Are you working on an expansion and are you curious about the possibilities, please contact us. A team of designers and constructors is ready to help you on your way. For example, if you are curious about which type of foundation is needed for your expansion, we can perform a quick scan of the soil conditions, so that advice can be quickly given on the type of foundation to be used.