A sandstone wall grouting

Sandstone has always been a popular building material. The building material is used as in old building renovation as well as in the construction of a natural stone wall. If a sandstone wall is not designed as a drywall, it must also be grouted. However, grouting a sandstone wall requires expertise in building materials. Therefore, below we have compiled information for you how a sandstone wall should be grouted.

What is sandstone?

Sandstone is a sedimentary rock. It is caused by deposits, especially in oceans, rivers and lakes. Therefore, there are numerous sandstone quarries today in the regions of ancient lakes, prehistoric seas and primeval rivers. Even sand-lime bricks belong to the sandstone deposits. One of the most famous rocks of this type comes from the Swabian Alb (Jura limestone).

Properties of sandstones

Sandstone is very soft, so easy to work. This in turn has meant that sandstone has always been used by people as building material. In Europe, the oldest sandstone structures are found by the Romans. Also in relation to the grouting of sandstone walls can be derived from these ancient buildings a lot.

Sandstone - a traditional building material

Often, the Romans used Opus Caementitium for walling and grouting, a type of concrete whose hardening properties are based on the provided pozzolans. This often volcanic rock is also available here in Germany under the name Trass. There is a reason why we go so far: it is often recommended to grout sandstone walls with trass mortar. In addition, water-repellent cement often comes as a recommendation to wear.

Not every antique construction technique is suitable as a tip

If you take a closer look at ancient Roman structures such as viaducts, you will notice that they were working with trass or Opus Caementitium. But it can also be observed that the sandstone weathered more and more and only the mortar and grout material remains.

The fugue should always be softer than the surrounding stone work

But this grout and mortar material now offers a receiving surface for water, which can penetrate into the remaining sandstone. Thus, the already mentioned building materials for plastering sandstone walls are clearly not recommended. Instead, over the centuries a rule of thumb has prevailed among specialists that you should follow without restriction: mortar and grout should always be softer than the brick wall. Or vice versa: the bricked brick should be harder than the grout.

The optimal building material for sandstone joints

From this it can be concluded that the used Fugenzement should never have too strong setting properties. Instead, you should instead achieve a coarser grain of the Fuentenements. You can use the following building materials:

  • NHL mortar (includes natural hydraulic lime)
  • Air lime mortar, different grain sizes

Which grain sizes you need for grouting depends on whether you want to rehabilitate an old wall that has already weathered or whether it is a new building.

Procedure for old sandstone walls

  • Clean joints of loose and porous plaster or mortar (scratch out)
  • clean the surface of the sandstone wall
  • clean the cleaned surfaces with alumina solution (o, diluted 4%)
  • Deep grouting with up to air lime mortar with a grain size of up to 4 mm
  • final surface grouting with a grain size of approx. 1 mm

Procedure for new sandstone structures (walls)

The clay solution ensures a very good adhesion of the quicklime mortar. Therefore, its use is also recommended when grouting new sandstone walls. Depending on the joint size for new sandstone walls, you should pay attention to a grain size of about 2 mm. Nevertheless, the final grain size of the mortar also depends on the joint size.

Tips & Tricks

Sandstone is a very versatile construction material. You can not use these stones only for wet, mortared walls. Sandstone can also create a drywall. Such a drywall is ecologically particularly valuable as it will form a healthy ecosystem if you plant such a sandstone drywall accordingly.

Video Board: How to use a grout bag Grouting veneer stone Part 1