Building with AAC Notes

Building with AAC

About Xella

Xella has 96 own factories in 20 countries and sales organizations in over 30 countries.
Xella Building Materials is the largest business unit of the Xella Group.
Xella brands: Ytong, Silka, Multipor and Hebel.
Xella is a leading manufacturer of autoclaved aerated concrete and calcium silicate products.
Xella building materials have gained customer loyalty and have been bestowed with numerous awards and certifications.
Xella manufactures and markets building materials and drywall solutions together with lime and limestone.
The Xella Group is a leading building materials company in Europe.

Content

Ytong - distinctive building with autoclaved aerated concrete (pages 4-5)
General introduction to the use of Ytong AAC (pages 6-13)
Construction of load-bearing masonry (pages 14-19)
Construction of non-load-bearing masonry (pages 20-25)
- Infill masonry (pages 20-23)
- Internal partition walls (pages 24-25)
Supplementary products (pages 26-28)
Follow-up work (pages 29-45)
- Interior surface treatment (pages 33-36)
- Exterior surface treatment (pages 37-45)

Ytong - Distinctive Building with Autoclaved Aerated Concrete

*Ytong Advantages:

Energy Efficiency: Reduces heating and cooling costs.
Fire Resistance: Offers up to six hours of fire protection.
Breathable: Moderates moisture levels.
Lightweight: Reduces freight and construction costs (approximately ¼ the weight of traditional concrete).
Outstanding Strength: Can bear several floors, especially in seismic areas.
Quickly Installed: Easy to install on site and can be sawn or drilled.
Accuracy: Provides optimal dimensional accuracy.
Soundproof: Provides effective sound insulation.
Versatile: Can be cut to any shape or angle.
Durable: Will not degrade under normal atmospheric conditions.
Ecology: Certified as one of the most environmentally sustainable building materials and is nontoxic.
Recyclable: Byproducts are recycled back into the production process.
Ytong AAC serves architects, planners, builders, and owners of private and commercial buildings and can be found in any kind of building.
Ytong AAC focuses on efficiency, innovation, and perfection.

General Introduction to the Use of Ytong AAC

Ytong autoclaved aerated concrete products are high-quality masonry products.
The products undergo regular quality inspections during the manufacturing process.
*Tools:
Mortar trowels: Scoop-style mortar trowels are available with various notch patterns and in different widths to suit all wall thicknesses; they make it easy to apply the correct amount of thin-bed mortar to give a full-fill bond.
Rubber mallet: A rubber mallet is used to tap the masonry units into the fresh mortar bed and align them plumb and level.
Spirit level: A spirit level is used to check that the blockwork is plumb and that the bed joint is sufficiently level to lay the next course of blocks using the thin-bed system. We advise using long spirit levels ( $\geq$ 200 cm).
Paddle mixer: Thin-bed mortar is mixed in a mortar bucket in accordance with the instructions. To obtain the desired consistency it is advisable to use a particularly low-speed mixing machine (or drill) and a robust mixer with long paddles. Paddle mixers should be thoroughly cleaned after use.
Ytong sanding board and Ytong rasp: Ytong AAC can also be sanded down if the blockwork is out of level or plumb. A sanding board is sufficient for removing small amounts of material. If larger amounts of material have to be removed, use the Ytong AAC rasp. This can be followed by a second sanding if necessary. In both cases the sanded surface must be carefully swept afterwards to ensure that the thin-bed mortar forms a strong bond in the bed and head joints.
Ytong wall chaser: The Ytong wall chaser provides a simple means of forming grooves up to 3 cm deep in Ytong walls (e.g. for electrical connections).
AAC hand saws [8] in combination with an angle guide [9] designed for cutting AAC, electric hand saws [10] with a suitable saw blade, or band saws [11] allow for precision cutting.
*Scaffolding:
- A masonry stepladder makes it easy to lay masonry blocks on low wall sections.
- Larger and higher wall sections require stationary scaffolding, which should be erected in accordance with the applicable safety requirements to ensure health and safety in the workplace.

*Mortar:

Ytong products should be used only with the mortar supplied by Ytong or an alternative brand of mortar recommended by Ytong.
Thin-bed mortar: Ytong AAC products are manufactured with very small dimensional tolerances and are therefore suitable for the thin-bed construction method. The easiest approach is to use Ytong AAC with a thin-bed mortar formulated specifically for use with the masonry.
- The use of premixed mortar is governed by European product standard EN 998-2.
- It consists of cement-based mortar in mortar class GIII as defined in EN 1996-1 with a dry bulk density of over 1500 kg/m³.
- European standard EN 998-2 defines thin-bed mortar as class M10 or above with quick-setting cement and a minimum compressive strength of 10 N/mm².
- Mix using a mortar mixer with speed control, leave to cure briefly, then mix again.
- The mixed mortar has a processing window of up to four hours, depending on the weather.
- Apply the mortar to fully fill the bed joint using a suitable trowel. The ridges of mortar produced by troweling should not run into one another or be broken as this indicates that the mixture does not have the correct consistency and should be discarded.

*General-purpose mortar:

*   This construction method requires the first course of blocks to be completely level. This is done by laying the first course of blocks (the foundation or kicker course) in a bed of conventional mortar to even out any unevenness in the floor or ceiling slab.
*   With high-quality masonry, a pure cement-based mortar is used for this purpose.
*   Pure cement-based mortar consists of sand and cement in a ratio of 1 part cement to 4 parts sand.

*Waterproofing membranes:

Masonry structures must be protected from moisture ingress.
Horizontal damp-proof membranes: A horizontal moisture barrier comprising at least one layer is required for any masonry construction and is inserted underneath both the external and internal walls.
- The damp-proof membrane must protrude at the sides and be suitable for connecting to vertical and other horizontal membranes.
- For structural reasons, horizontal damp-proof sheeting or a damp-proof seal with equivalent frictional resistance should be used.

*Bed joints in masonry:

*   Bed joints must always be fully mortared.
*   Bed joints filled with thin-bed mortar should be 0.5 to 3 mm thick.
*   Thin-bed mortar trowels developed by Ytong and available in widths to suit all wall thicknesses are ideal for ensuring professionally executed masonry with flawless, fully mortared joints.

*High-quality execution of overlaps:

Ytong autoclaved aerated concrete must always be used in accordance with the applicable design standards for masonry construction.
To ensure high-quality workmanship, it is important to comply with the overlaps indicated in the structural analysis and design documentation and to have them regularly checked by the site supervisor from the start of construction.
*Correct laying of masonry without mortared head joints:
Ytong autoclaved aerated concrete can often be laid using the tongue and groove joints on the header faces without mortaring the head joints.
Tightly butted head joints up to 5 mm wide do not have to be mortared unless fire safety or smoke containment requirements call for a gapless joint.
For walls that are not subject to special structural requirements (i.e. fire protection or sound insulation), it is sufficient to seal the head joints close to the surface, otherwise, at least 50% of the depth (half the width of the block) must be mortared across the entire block height.
*Correct laying of masonry with mortared head joints using thin-bed mortar:
The head joints of tongue and groove masonry can also be mortared using suitable thin-bed mortar and tools. This may be stipulated in the structural analysis (e.g. in the case of seismic loading), the construction plans, or the fire safety requirements.
*Wall connectors (ties):
Masonry contributes to the building’s structural rigidity by means of individual, interconnected shear walls.
Wall connectors are typically attached using the butt joint method, which gives them tensile and compressive strength, and have to be verified by structural analysis.

*Protecting fresh masonry for a long service life:

Freshly constructed masonry must be protected from external influences.
Wall copings and parapets should be covered at the end of the working day and standing water at the foot of the wall should be avoided.

*Ceiling construction:

*   Ceilings should not be installed until the mortar has had sufficient time to cure, and once in position, heavy reinforced concrete ceiling slabs should not be moved.

*Working in very high temperatures:

Additional measures are required when working at temperatures in excess of 30 °C.
The water added to the mortar mix evaporates significantly more quickly during hot weather, which means that there may not be sufficient water for the curing process.
To counter this effect, we advise wetting the blocks with a brush.

*Working in very low temperatures:

It is important to check whether local standards and provisions permit masonry work to be carried out during freezing weather.
The use of antifreeze additives is not permitted since these can adversely affect the setting behavior and characteristics of the mortar.
Completed masonry work must be protected with a thermally insulating protective cover during winter months.
*Health and safety on construction sites:
- All construction personnel should make health and safety a top priority.
- Construction site personnel must be familiar with personal protective equipment (including safety shoes, clothing, head, eye and ear protection) and use it correctly as a safety precaution.

Construction of Load-Bearing Masonry

*Laying the first course:

A floor or ceiling slab does not provide a completely flat surface since height variations occur during the smoothing and leveling process. These irregularities can be overcome by setting the first course of blockwork in general-purpose mortar in mortar class GIII (as per Eurocode 6).
At least one horizontal barrier membrane (e.g. R 500 bitumen sheeting) should be inserted in the lower floor to protect against rising damp. Standards may specify a mineral-based waterproofing slurry as an alternative horizontal waterproof membrane.

*Laying the second course

When the first course of the entire building is completed, remove any uneven areas with the sanding board or rasp so that the second course can be laid completely level.
Brush any dust and loose material off the bed joint after sanding.
Then apply Ytong thin-bed mortar with a trowel.

*Structural connections

A tied junction is the usual method of connecting autoclaved aerated concrete masonry walls. When individual walls have been completed, the bracing walls are butted up to them using wall ties.
The wall ties are inserted halfway into the mortar of the bed joint where the bracing wall intersects to ensure a strong bond. The number of ties is determined by the structural requirements.
*Design recommendations for corners and parapets:
- External corners with a wall thickness $\leq$ 365 mm: For external corners with a block width $\leq$ 365 mm, we generally recommend systematically mortaring the head joints of the cornerstones.
- External corners with a wall thickness > 365 mm: For external corners with a block width > 365 mm, it is common practice to start at the corner with Ytong block cut in half. We generally recommend this approach in any case to maintain the overlap of \lol \geq 0.4 \cdot h. It is also advisable to systematically mortar the head joints of cut blocks and to insert Ytong wall ties or alkali-resistant glass fiber reinforcement mesh in each bed joint.

*Constructing parapets:

*   **Variant 1:** Insertion of a steel reinforcement bar with a 10 mm diameter into the final bed joint: Make a groove with an AAC wall chaser [15], insert the reinforcement bar in the groove [26] and fully embed it in at least 2 cm of general-purpose class GIII mortar (as per Eurocode 6) [27]. Make sure that at least 50 cm at each end of the rod is also embedded in the masonry [29).
*   **Variant 2:** Insertion of an alkali-resistant glass fiber reinforcement mesh into the final bed joint [30]: Fully embed the reinforcement mesh in the thin-bed mortar and anchor at least 50 cm into the masonry at each end. For a block width of 20 cm or more, place two reinforcement strips side-by-side in the bed joint and embed them fully in mortar.

*Protecting the tops of walls:

*   It is essential to cover the tops of walls and copings at the end of the working day and during prolonged stoppages to protect the finished masonry from moisture penetration.

Construction of Non-Load-Bearing Masonry

The compartments in the external facade are generally closed with non-load-bearing masonry known as ‘infill’.
*Rigid connection:
Mortar joints with thin-bed mortar or class GIII mortar (as per Eurocode 6) between the infill masonry and the steel or reinforced concrete columns.
*Flexible connection:
A joint filled with mineral wool or polyurethane foam between the infill masonry and the steel or reinforced concrete columns.

*Laying the first course:

The first course of masonry determines the orientation of the entire infill wall. Lay the first course in a bed of general-purpose mortar in mortar class GIII (as per Eurocode 6) to even out any differences in height.

*Laying the second course

Ytong blocks are always bonded with an overlap of at least \lol \geq 0.4 \cdot h . To achieve this, start the second course with a half block; blocks can easily be cut using an AAC saw.

*Non-positive connection between structural framework and infill masonry:

Normative requirements and certain load actions (e.g. earthquakes) may make it necessary to connect the infill masonry to the framework in a non-positive way.

Internal Partition Walls

Partition walls achieve structural stability only when connected to adjacent structural components.
It is always advisable to fit a horizontal damp-proof membrane in partition walls in bathrooms/WCs.
*Construction recommendations for all non-load-bearing internal partition walls
- Mortar the head joints of all non-load-bearing internal partition walls
- Limit deflection from overhead ceilings
- Reduce ceiling deflection as a result of shrinkage and creep by observing formwork stripping times and finishing the concrete. Use suitable intermediate supports if stripping times are short
- Construct partition walls at as late a stage as possible, e.g. after completing the building shell
- Protect partition wall material from severe moisture penetration, e.g. with films
- Separate the partition wall from the floor/ceiling, e.g. with film or bitumen sheeting, to divert potential cracks in the wall from the ceiling to somewhere out of sight
  *Rigid connections
- Rigid connections are formed with steel inserts, mortaring, interlocking systems etc. They are suitable for use in situations where there are not expected to be any major restraint forces and deformations from the wall or adjacent load-bearing structures.
  *Floating connections
- Floating connections at the sides or above are formed with grooves or steel profiles backfilled with mineral fiber strips and with anti-frictional layers applied to contact surfaces if necessary. The non-load-bearing internal partition wall is laid in a bed of mortar at the foot of the wall. With larger ceiling spans, bitumen sheeting is inserted in the masonry to prevent the wall cracking as a result of ceiling deflection. Reinforcement strips inserted in the bed joints are an additional precaution to prevent cracking. These are inserted as specified in the structural analysis.

Supplementary Products

*Ytong leveling block

Leveling blocks are mainly used as a kicker course to offset height differences or differences in shell height without making additional cuts.
The method of laying them and the tools required are the same as for standard precision blocks.
Ytong leveling blocks can be used at the top if the height of the building shell cannot be achieved with the ‘course dimensions’ of standard blocks.

*Ytong lintels

Ytong lintels are ideal for use in combination with Ytong wall systems because they share the same physical and structural properties as solid AAC masonry.
- Non-load-bearing Ytong lintel: With a length of 1.25 m, the non-load-bearing lintel made from reinforced Ytong AAC is available for thin wall thicknesses and for openings with a clear width of up to 1.02 m.
- Load-bearing Ytong lintel: The load-bearing reinforced AAC Ytong lintel can be used in load-bearing and non-load-bearing walls. It is available in sizes to suit all conventional wall thicknesses and designed for clearances of up to 1.75 m.
- Ytong flat lintel: Flat lintels are prefabricated lintels with a low ‘processed weight’ for door and window openings in AAC masonry [9]. Both the bearing face and head joints of Ytong flat lintels must be fully mortared with thin-bed mortar.

*Ytong U-block

The Ytong U-block is an unreinforced framework block that is used mainly to accommodate beams, columns, and ring beams. It can also be used to form vertical slots and support columns in AAC masonry.

Follow-Up Work

In order to retain the positive characteristics of Ytong wall materials in the long term, various follow-up measures are required to protect the masonry and customize the finish.
*Wall chases and channels:
- To ensure that chases in Ytong wall materials are properly constructed, the values in Table 1 as per EN 1996-1-1 (Eurocode 6) and the corresponding national annexes must be complied with.
- Chases and channels weaken the wall cross-section and should therefore be kept to a minimum.
- With the aid of suitable tools, it is easy to cut chases in Ytong masonry. Structurally destructive tools such as electric drills and chisel hammers are totally unsuitable for this type of work.

Interior Surface Treatment

Ytong masonry structures generally require a durable surface treatment: This protects against moisture, ensures air tightness, protects the indoor climate from the effects of aggressive environmental influences, increases mechanical resistance and last but not least, improves the visual appearance.
*Interior plaster
- The interior is precisely the place to use products designed for healthy living which are free from solvents, volatile organic compounds (VOCs) and plasticizers.
- For wet areas we recommend interior plaster containing cement, whilst lime or gypsum plasters are ideal for living areas.
  *Applying interior plaster
- The Ytong AAC substrate should be free from residues that may impair adhesion in accordance with the interior plaster manufacturer’s specifications – so make sure that all dust and loose particles have been brushed off.
  *Individual finishes for internal plaster
- In addition to the various types of smooth plaster described here, numerous other surface textures can also be created with interior plaster.
  *Paint
- Conventional emulsion paints can be applied directly to mineral substrates such as Ytong AAC to give a uniform color without damaging the structure of the processed stone and masonry.
  *Interior wall tiles
- As a result, ceramic tiles can be applied directly to the masonry.

*Wood panels and panel-like wallcoverings

If decorative interior wood panels or panel-like wall claddings are to be mounted on top of Ytong AAC, we recommend first applying interior plaster to ensure airtightness.

Exterior Surface Treatment

All masonry structures require a durable surface treatment with the exception of exposed masonry.
*Exterior render on Ytong AAC masonry above the plinth:
- An exterior render must have good adhesive characteristics and be vapor-permeable, flexible, water-repellent and weather-resistant to provide adequate protection from rain.
  *Exterior render on Ytong AAC masonry in the plinth area:
- The plinth is the lower part of the facade and is therefore exposed to soiling from rainwater splash.
  *Vertical waterproofing of Ytong elements in contact with the ground:
- Ytong masonry in contact with the ground requires a durable, functional waterproof membrane which should basically satisfy the following requirements: The effectiveness and durability of a masonry seal depends not only on its correct design and execution, but also on the masonry elements that are to be waterproofed; they too must be designed, dimensioned and executed in a manner that lends itself to subsequent waterproofing.
  *External thermal insulation composite systems on Ytong wall materials:
- There are various external thermal insulation composite systems (ETICS) on the market to suit all energy ratings which are suitable for use with Ytong AAC. ETICS are regulated by approvals which must be complied with to ensure that they are correctly installed so as to give facades the necessary fine detailing and desired surface finish.
  *Exposed facing masonry:

*Modern: Single-block wall, in which the wall thickness corresponds to the block thickness.

*Back-ventilated facade:

*   External walls with back-ventilated cladding are the perfect solution in terms of their hygrothermal performance.

*Fixtures
*AAC square-cut nail Cavity wall tie