Gluing Ytong Bricks: DIY Instructions | Glue With What?

Gluing Ytong Bricks: DIY Instructions | Glue With What?

Ytong stones are very popular due to their good workability and versatile range of services. Thanks to modern processing methods, walls that are not always very simple are no longer necessary. Instead, Ytong stones can be glued and thus moved quickly and with high dimensional accuracy. You can find out from us how do-it-yourselfers can do this without any problems.

Ytong is one of the most common materials for the construction of solid, i.e. usually brick walls. Due to its high insulating properties in connection with its static load capacity, it is a popular choice for exterior walls, but it is also repeatedly used indoors. The simple handling allows experienced do-it-yourselfers to work with Ytong stones themselves in the do-it-yourself process with little effort and at the same time great success. You can find out how to glue the stones together here.

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What is Ytong?

Before you start gluing Ytong stones, you should ask yourself which material is actually being processed here. Because from the knowledge of its peculiarities, various aspects of processing arise almost automatically. Ultimately, Ytong is aerated concrete, i.e. a mixture of:

  • Sand
  • lime
  • cement
  • Air formers such as aluminum salts

In contrast to a brick, which consists of comparatively solid material with empty air chambers in between, an aerated concrete block is created homogeneously. The mixture is foamed during the manufacturing process and, like a sponge, has countless tiny pores. The insulating properties and static load capacity are determined by the ratio of air voids to concrete. The more pores, the better the stone insulates. In return, the compressive strength decreases. In addition, the material has other technical properties that you should know in order to avoid serious mistakes when gluing Ytong stones:

  • Relatively soft substance of the material, so there is a high risk of fractures or chips when hitting corners, sawing thin cuts, etc
  • The porous material has absorbent properties, so no water-binding adhesives can be used
  • Usually manufactured as a flat block, thus high dimensional accuracy; for precise work results, high precision is also required during processing

Note: The designation Ytong stones is originally a brand name, but today it has become a synonym for aerated concrete blocks in general usage. But just as not every handkerchief is a Tempo, there are of course numerous other manufacturers whose products are characterized by comparable properties. The following instructions can therefore also be applied to aerated concrete products from other manufacturers at any time.

Choosing the right stones

Before you can start gluing the aerated concrete, you have to choose the right product from the wide range of different stone types:

1. For components that are not statically relevant, such as brick walls, non-load-bearing interior walls, etc.:

  • Select stone thickness according to local requirements
  • Choose stone dimensions according to area, the more corners, angles, joints, etc., the smaller the stone format, use large-format blocks for large wall areas

2. For structurally relevant components:

  • Observe the specifications of the structural engineer and have the stone type checked and approved by him before purchase!

ATTENTION: In addition to the statics, legally prescribed insulation values ​​may also have to be observed. Before processing, it is essential to clarify with the planner whether the Ytong bricks in question meet all the requirements.

How do you glue Ytong bricks?

Once you have found the right Ytong bricks, gluing them together is very easy and very successful. However, you should still pay attention to a few things and it is best to follow these instructions:

General Processing

Ytong stones are manufactured as so-called plan stones. This means that their dimensions are worked out so precisely that the classic mortar joints for alignment can be omitted. Placed on top of each other without mortar, they would usually result in a straight, vertical wall. Within a row of bricks, they can actually be lined up without glue in the sense of a tongue-and-groove construction through existing pockets. The individual layers are glued together with a so-called thin-bed mortar or thin-bed adhesive. A very even application of the adhesive is particularly important. Because only if the layer of adhesive is the same thickness everywhere can the great strength of the planing stones come into play.

The right glue

Common adhesives for gluing Ytong bricks are cement-based thin-bed mortar. This means that the adhesive sets on the basis of a chemical reaction and is waterproof once it has completely hardened. Due to the identical binder cement, the adhesive corresponds overall to the properties of the stone. It is important to only use adhesives that are specifically approved for thin-bed processes and in connection with aerated concrete blocks. Ideally, the stone manufacturer’s adhesive ensures that all components are coordinated and deliver optimal results. The adhesive is mixed with water similar to concrete. For a dimensionally accurate bonding result, the manufacturer’s instructions should be followed. Since the consistency has a great influence on the workability, you should never mix too much glue at once. You can see with the naked eye whether it can still be processed:

  • Running lines of glue = consistency too thin
  • Tearing snakes of glue = hardening too far advanced or insufficient water content
  • Uniform strings of glue that are stable on their own = workable consistency

Tip: As a test for the right consistency and amount of glue, you can place a stone on the glue bed and then lift it off again. If the underside is completely covered with adhesive without excess dripping off the edges, the amount of adhesive is correct.

The right tool

For dimensionally stable walls, an even application of adhesive over the course of the individual rows of bricks is essential. The following are therefore ideally suited:

  • notched spatula
  • notched trowel
  • Special glue slide
notched spatula

All of these tools are designed with a serrated application edge. This toothing creates uniform snakes of adhesive mortar at equal distances from one another when the adhesive is pulled off. Excess mortar is wiped off. It is important to always use the same tool over the course of a stone layer, as different tools can have different opening sizes. It is ideal to use the tools specified by the manufacturer, since the amount of adhesive applied then harmonizes with the requirements of the individual stone in any case.

First location

Since the aerated concrete blocks are inherently extremely dimensionally stable, they can be processed on the surface without any major inaccuracies. The basic requirement for this is that the first layer of stones is laid plumb and flush. Therefore, the first layer of stones is of particular importance:

  • When erected on the lowest floor: lay a single-layer bitumen sheet under the wall,
  • Ensure that the barrier membrane overhangs the future wall on both sides for the connection to the floor waterproofing, select the membrane width depending on the wall thickness: eg for a 11.5 cm wall 25 cm of barrier membrane
  • Specify the course of the wall with a guide line at the height of the first layer of bricks, fix the line, for example with a nail, in the existing connecting walls
  • Before the first layer of stones, check the substrate for evenness and horizontal alignment
  • In the case of unevenness: apply a smooth coat of cement mortar to the barrier sheeting, smooth the upper edge with a straightedge and check the height using a meter mark or a laser spirit level
  • First stone layer with thin-bed mortar on a smooth finish

ALTERNATIVE: Place the first layer of stones directly in the cement mortar and align plumb and flush using a spirit level and plumb line.

Note: Setting the first layer of stones requires some skill and experience. If you feel unsure, you should have this important step carried out by a specialist. Since the walls can then be walled up afterwards without any problems, this still saves a great deal of skilled worker time and therefore money.

The wall surface

After the first layer of stones, the rows of stones are glued in layers. Due to the quick setting time of the adhesive and the small application thickness, row after row can be stacked without major delays or waiting times:

  • Spread the adhesive evenly along the wall with a notched trowel or similar
  • Place and align stone by stone from its wall side
  • Insert the follow-up stone fully into the existing pocket of the stone that has already been set in order to avoid gaps and joints
  • Execute rows completely, only then tackle the following row
  • Regularly check alignment with a straightedge or plumb line
  • Check the vertical wall structure after each layer of stones with a spirit level


Whether at the upper end of the wall towards the ceiling or in the connection area to other walls – again and again the work cannot be completed with whole stones. Due to their relatively soft nature, Ytong stones are very easy to cut. Either a cut-off grinder with a stone blade can be used, or a manual Ytong saw is used. It is important that remaining cross-sections that are too small usually lead to breakage, since the inherent stability is correspondingly low. Here it can make sense to cut two stones only slightly, instead of a whole stone and a leftover piece, in order to obtain parts that are easy to process.

Upper wall connection

Although not specifically and exclusively used when gluing Ytong bricks, one should not forget to observe the special requirements of the upper wall connection:

1. For non-load-bearing walls:

  • no force-locking bond between wall and ceiling, otherwise cracks will form due to wall pressure
  • Lay cork or foam strips between the top row of stones and the ceiling as static decoupling

2. for load-bearing walls:

  • in the case of subsequent installation, fill the gap between the top row of bricks and the ceiling with mortar over the entire surface
  • in the case of later ceiling construction: bring the uppermost bricks to the desired height with cuts, mortar out gaps between prefabricated ceiling parts etc. after ceiling installation

Tip: Instead of laboriously cutting stones for sections, the manufacturers also offer prefabricated shaped pieces for recurring cases. Especially for wall heights that do not go up in whole stones, so-called cinder blocks allow the completion with thinner stone slices without cutting.

The post-processing

Normally, the correctly created walls do not require any immediate post-processing, since the Ytong stone gluing has been specially perfected for an economical and uncomplicated process. However, if you don’t do it properly with too much glue, you may have to knock off or grind off the glue noses. If, on the other hand, excess adhesive mortar is removed with a trowel while it is still wet, this step is not necessary.