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Dimensional tolerances for tile and slab work

The tile and slab work includes the attachment and laying of ceramic tiles, slabs and mosaic, natural stone tiles, natural stone mosaic and natural stone cladding. When assessing dimensional tolerances in tile and slab work, a number of questions and problems arise.


The tile and slab work includes the attachment and laying of ceramic tiles, slabs and mosaic, natural stone tiles, natural stone mosaic and natural stone cladding.

The attachment and laying of other slabs made of natural or artificial stone is not part of the tile and slab work, but belongs to the natural or artificial stone work.

In the VOB / C are the Tile and slab work regulated in ATV DIN 18352.

Possible problems due to dimensional or flatness deviations

When assessing dimensional tolerances in tile and slab work, a number of questions and problems arise. First of all, it must be clarified why the dimensional tolerances should be checked. Occasions for this can be, for example:

  • Built-in parts from subcontractors, e.g. door frames, built-in furniture, sanitary items, electrical installation parts etc. do not fit into the openings, niches or the like.
  • Wedge-shaped or uneven joints in the connection area to built-in parts, e.g. between wall surface and frame
  • Wedge-shaped or uneven connection or shadow joints between components, e.g. between walls and suspended ceilings
  • Concerns from successor trades, e.g. carpenters, heating and plumbing installers or electricians, due to non-compliance with the permissible tolerances
  • Disturbance of the appearance or the function, e.g. due to the risk of tripping, due to recognizable unevenness
  • Disturbance of the appearance due to the uneven course of joints and edges

Causes of dimensional tolerances outside of the tile and slab work

In order to assess alleged or actual defects with regard to the dimensional tolerances, however, it must also be examined whether these are actually due to the tile and slab work or whether there are other influencing factors. The following should be mentioned in particular:

  • load-dependent deformations
  • time-dependent deformations (creep, shrinkage)
  • thermal deformations

The unevenness of a tiled floor can also be caused, for example, by bending of the raw ceiling under load. In such cases it can be very difficult to determine what proportion of the lack of unevenness is due to the deformation of the substrate and what proportion of deviations in the flatness of the tile and slab work, if the deformation was not already present before the tiles or slabs were laid. Therefore, checks of the tolerances should always be carried out as early as possible, preferably immediately after completion of the service.

Deformation of the subsurface can have very far-reaching effects. For example, puddles or counter-slopes can form in the floor areas of balconies. Therefore, such expected deformations must be taken into account by the planner at an early stage.

If the contractor realizes that later deformations can cause problems, he should accordingly ATV DIN 18352, section 3.1.1 inform the client of his concerns in good time, i.e. before the start of his work.



Regulations on dimensional tolerances for tile and slab work can be found in the following standards:

  • ATV DIN 18352 tile and slab work
  • DIN 18202 tolerances in building construction
  • DIN 18065 building stairs - terms, measuring rules, main dimensions

If the VOB has been agreed as part of the contract between the client and the contractor, this automatically includes DIN 18202. For tile and slab work on stairs, DIN 18065 must also be observed, although this is not listed in the ATV.

DIN 18202 tolerances in building construction

According to Section 4.5 of the standard, the tolerances specified in DIN 18202 represent the basis for fit calculations in the building industry. Correspondingly, DIN 18202 in Section 4.2 states that the tolerances specified in it must be adhered to so that the relevant components can fulfill their function and the assembly of the components is possible without adapting or reworking.

In relation to the tile and slab work, this means that a check of the tolerances according to DIN 18202 is only to be carried out in the following cases:

  • before starting the tile and slab work to check the preliminary work of other trades, in particular compliance with the limit values ​​for angular deviations and for deviations in flatness of the surfaces to be covered, so that the contractor can assert his concerns to the client if the tolerances of the respective components are exceeded
  • after completing the tile and slab work:
    if it turns out during the installation of components that wall surfaces are not perpendicular or floor surfaces are not horizontal or with the required slope or that these components are uneven
    - if it turns out during the installation, e.g. of frames, built-in cupboards, sanitary objects, etc., that the dimensions have not been adhered to
    - during the review by subsequent entrepreneurs as part of their review of preliminary work, so that they can raise their concerns if necessary
    - at the acceptance of the tile and slab work, so that it can be proven that the performance meets the requirements for the tolerances

The individual dimensional tolerances according to DIN 18202 can be applied to tile and slab work as follows:

Limit deviations

The height of the tile surface of floors in relation to a reference area, which is usually defined by a height reference point (meter line), must meet the requirements of DIN 18202, Table 1, Line 2. The nominal distance of the floor surface based on a height reference point is usually exactly 1 m, according to table 1, column 2, a limit deviation of ± 10 mm is permissible.

Deviations from the limits are to be taken into account when working with tiles and slabs, such as platform heights, heights of fully covered masonry, clear dimensions of openings and niches, finished thicknesses of free-standing wall panels to be covered on both sides, e.g. shower partitions, or when setting up tile partitions and partition walls made of cell wall stones.

When the contractor checks the preliminary work of other entrepreneurs, e.g. checking the location of brick walls, the height of masonry, platforms, steps, etc., the same limit deviations apply, but based on the nominal dimensions for these unfinished components. Therefore, the distance between the upper edge of a screed to be covered with tiles and the meter line according to DIN 18202, Table 1, has a limit deviation of ± 16 mm.

In the case of clear dimensions of openings, the lower requirements for limit deviations according to DIN 18202, Table 1 apply to the preliminary work, provided that the reveals are not already plastered, which, like the reveals that may then be covered with tiles, are part of the surface-ready reveals.

Limit values ​​for angular deviations

The limit values ​​for angular deviations are relevant in many areas of tile and slab work:

Wall surfaces, wall panels:

  • Deviation from the vertical in the elevation
  • Deviation from the specified plane in the case of inclined walls
  • Deviation from the given position in the floor plan

Floor, platform areas:

  • Deviation from the horizontal
  • Deviation from the specified level for surfaces with a slope
  • Deviation from the position of specified edges

Openings, recesses, niches, etc.:

  • Deviation from the vertical, horizontal or other specified angle with regard to position and shape

These limit values ​​also apply when checking preliminary work in accordance with ATV DIN 18352, Section 3.1.1.

Limits for flatness deviations

The flatness of the surfaces must be within the limit values ​​for flatness deviations according to DIN 18202, Table 3. Without any further contractual agreement, the values ​​from lines 3 and 6 of this table are decisive. If the client places increased demands on the evenness of the surfaces, then the stricter limit values ​​according to line 4 or 7 of the table must be observed.

DIN 18065 building stairs - definitions, measuring rules, main dimensions (Table 1)

DIN 18065 contains permissible tolerances for stairs. These are also to be observed by the tiler when covering stairs with tiles or slabs. The tolerances in this standard are specifications for the finished staircase.

In section 7 of DIN 18065, the following permissible dimensional deviations are specified:

  • Permissible deviation from the nominal dimension of the staircase incline: ± 5 mm
  • permissible deviation from the nominal dimension of the stair tread: ± 5 mm
  • permissible difference between the actual dimensions of two adjacent steps: 5 mm
  • In the case of spiral stairs, a deviation in the stair tread in the area of ​​the spiral of up to 15 mm is permissible if this results in a constant step pattern.
  • In the case of stairs in residential buildings with no more than two apartments, the actual gradient of the first step may deviate from the nominal size by a maximum of 1.5 cm.
  • The maximum gradient according to DIN 18065, Table 1 must not be exceeded by tolerances.
  • The minimum tread dimension according to DIN 18065, Table 1 must not be undercut due to tolerances.

Tab. 1: Limiting dimensions for usable stair flight width, stair incline, stair tread

Stair typeUsable running width [cm]Pitch s [mm]Step a [mm]
at leastat leastMax.
Limits for buildings in general
Staircase required by building law100140190260370
unnecessary stairs50140210210370
Limit dimensions for residential buildings with up to two apartments and within apartments
Staircase required by building law80140200230370
unnecessary stairs50140210210370

Note on the table: The values ​​are to be adhered to in the finished final state.

The tolerances of Section 7 may not be counted towards the limit dimensions.

The usable flight of stairs may be restricted in the footwell by stringers.

  • Slope tolerances must lie within the tolerances of the nominal dimensions for stair incline s and stair tread a.
  • When installed, the tread surfaces of the steps may deviate from the horizontal position as a maximum:
    - in the flight of stairs: ± 0.5%
    - in the tread depth: ± 1.0%
  • In the finished state, the tread surfaces of the intermediate landings may deviate from the horizontal nominal position (target position) in each direction by a maximum of ± 0.5%, but not more than 1 cm.

ATV DIN 18352 tile and slab work

DIN 18352 applies to the attachment and laying of ceramic tiles, slabs and mosaics, natural stone tiles, natural stone mosaics, natural stone slips and Solnhofen tiles.

Examination of preliminary work

According to Section 3.1.1, the contractor has to check compliance with the tolerances according to DIN 18202 for the preliminary work on which he is to build his services and, if he detects inadmissible excesses, the customer has to submit his concerns in accordance with § 4 Para / B to communicate.

Tolerances for tile and slab work (Table 2)

In section 3.1.2, the ATV states that dimensional deviations within the tolerances of DIN 18202 are permissible.

With regard to the joint widths, the ATV points out that joints should be evenly wide, but on the other hand dimensional tolerances of the tiles in the joints should be compensated for. According to Section 2.2.3 of the ATV, for example, sawn natural stone tiles up to 12 mm thick may deviate from the nominal dimensions of width and length of ± 0.5 mm. In the case of sawn natural stone slabs from a thickness of 12 mm, the deviations may be up to ± 1.5 mm in length and up to ± 1 mm in length and width. This makes it clear that by compensating for these tolerances within the joints, joints of the same width cannot be achieved. However, when attaching or laying, the tiler must ensure that he mixes and aligns panels with different permissible deviations from the nominal dimensions in such a way that the dimensional deviations of the panels do not result in particularly wide or particularly narrow joints, but rather joints that are as wide as possible.

Tab. 2: Joint widths according to paragraph 3.4.2

Type of clothing / surfaceJoint width
Ceramic tiles, dry-pressed, side length up to 10 cm1 mm to 3 mm
Ceramic tiles, dry-pressed, side length over 10 cm2 mm to 8 mm
ceramic tiles, extruded4 mm to 10 mm
Ceramic tiles, extruded, edge length over 30 cmat least 10 mm
Floor clinker plates DIN 181588 mm to 15 mm
Solnhofen tiles, natural stone tiles2 mm to 3 mm
Natural stone mosaic, natural stone brick slips1 mm to 3 mm

Other rules

In addition to the standards, there are also guidelines, leaflets and the like, which can also contain information on tolerances. However, these are only binding for the contractor if their validity is expressly contractually regulated.

Areas of application for tiles and slabs

For the consideration of the tolerances and their areas of application, the areas of application are referred to below

  • Indoor flooring,
  • Outdoor flooring,
  • Interior wall cladding,
  • Exterior wall cladding,
  • Put


Indoor flooring

Limit deviations

Permissible limit deviations for floor coverings are specified in DIN 18202, Section 5, Table 1. Since the tiler usually finds a finished laying area, he can have little or no influence on the local conditions.

Finished substrate / standard (Table 3)

In the standard case, both screed and tile or slab covering are based on the same permissible limit values ​​for deviations in evenness (DIN 18202, table 3, line 3).

Tab. 3: Permissible deviations in evenness for floor coverings and substrates for receiving floor coverings

Permissible flatness
Gauges as limit dimensions [mm] for measuring point distances [m]
up to 0.1> 0,1–1> 1–4> 4–10> 10–15
Substrates for receiving floor coverings24101215

Thick bed installation

When laying in a thick bed, deviations in the flatness of the sub-floor can be compensated for. Conventional installation in a thick bed is therefore preferable, especially if the existing installation substrate is irregular, but also if tiles and slabs of different thicknesses are to be installed. When laying tiles and slabs with thick beds, the bedding should have the following thicknesses in accordance with ATV DIN 18352:

  • Floor coverings in general: 20 mm
  • Floor coverings on the separating layer inside: 30 mm
  • Floor coverings on the insulation layer inside: 45 mm

Thin-bed installation

If tiles are to be laid in a thin bed, the subsurface must be particularly flat. With the thin-bed method according to DIN 18157-1 to -3, evenly thick, so-called calibrated (precisely cut after firing) ceramic and stone coverings are laid on an almost even substrate. Since it is hardly possible to compensate for unevenness with this method, the level of the subfloor must largely correspond to the finished usable area.

Outdoor floor coverings

The use of floor coverings outdoors is mostly limited to the areas of application of balconies and terraces. Regarding the dimensional tolerances, balconies and terraces are not to be designed differently than floor coverings in the interior, apart from special features such as necessary slope etc.


A missing or incorrect slope can cause structural damage, for example frost chipping. The planner has to consider the possible flatness and angle tolerances as well as any inherent deformations in his fit considerations. Correcting an incorrect or missing slope is often associated with considerable effort.

In order to safely divert water away from buildings, outdoor coverings must either be laid with a slope or, if laid horizontally, have a water-bearing underlay (drainage layer, etc.).

  • For surfaces outside, the gradient should be 1.5–3%.
  • The minimum slope of the subsurface should be 1.5–2%.

If panels are to be laid on a base with a slope, this should be checked. According to ATV DIN 18352, Section 3.1.1, the contractor must raise concerns if

  • the base has a missing or insufficient slope or else
  • the installed gradient deviates from the information in the construction documents.

Mortar bed thicknesses

Thick bed

The specified mortar bed thicknesses for laying outdoors are in accordance with ATV DIN 18352

  • 20 mm when laying thick beds in general and
  • 50 mm for thick bed installation with outer layers on separating layers.

There are therefore hardly any problems with regard to the evenness tolerances with this type of installation.

Thin bed

With a thin bed installation according to DIN 18517-1 to -3, it is hardly possible to level out unevenness. The substrate must therefore be particularly flat.

Panel joints

When laying tiles outdoors, you must also observe the minimum joint widths. If surface water is to be channeled through the joints into an underlying water-bearing layer (drainage layer, etc.), the planning and execution of the corresponding joint widths must be observed.

Interior wall coverings

There is no separate standard for the application of wall cladding inside the building. The relevant technical standards must therefore be applied during execution:

  • ATV DIN 18352 tile and slab work
  • DIN 18202 tolerances in building construction - structures

Unsurfaced substrates (Table 4)

According to DIN 18202, Table 3, the following flatness deviations are permissible for walls that are not ready-to-use, in comparison to walls that are ready-to-use:

Tab. 4: Permissible flatness deviations for walls / standard

Permissible flatness
Gauges as limit dimensions [mm] for measuring point distances [m]
up to 0.1> 0,1–1> 1–4> 4–10> 10–15
not finished walls510152530
ready-to-use walls (e.g. with wall plaster or cladding)35102025

The table shows that, as a rule, a tolerance of 5 mm must be compensated for in the mortar bed, since different requirements are placed on the evenness of the subsurface (not surface-ready) than the evenness of the wall cladding (surface-ready).

Finished substrates (Table 5)

The situation is different with substrates that are ready-to-use, for example a plastered wall surface or a drywall. The same requirements apply to the evenness of a plastered wall (ready-to-use) and the wall cladding (ready-to-use), assuming the standard case. If, however, increased demands are placed on the wall cladding, but not on the subsurface, differences in the bedding must also be compensated here (up to 2 mm for measuring point distances of up to 4 m, 5 mm for larger distances, see table below):

Tab. 5: Permissible evenness deviations for walls / standard requirements for the substrate and increased requirements for the cladding

Permissible flatness
Gauges as limit dimensions [mm] for measuring point distances [m]
up to 0.1> 0,1–1> 1–4> 4–10> 10–15
ready-to-use walls (e.g. with wall plaster or cladding)35102025
as above, but with increased requirements2381520

Wall coverings in a thin bed

If tiles and slabs are to be applied in a thin bed in accordance with DIN 18157-1 to -3, the substrate must therefore be particularly even. In the case of ready-to-use substrates, it should not show any greater deviations in evenness than permitted in accordance with DIN 18202, Table 3, i.e. it should meet increased requirements. In the case of subfloors that are not ready for use, laying in a medium or thick bed is preferable.

Laying in thick bed

When placing wall tiles and slabs in a thick bed, deviations in the flatness of the substrate can be compensated for. According to ATV DIN 18352, a thick bed for wall tiles and panels must have the following thickness:

This technique is therefore preferable if the existing substrate is irregular or large-format panels are to be used.

Exterior wall cladding

The execution of external wall cladding with tiles and slabs is regulated in the following standards:

  • DIN 18515-1 exterior wall cladding, mortared tiles or slabs
  • DIN 18515-2 external wall cladding, brickwork on contact areas

In the DIN 18515 series of standards, wall coverings are divided into:

  • mortared clothing
  • walled-in claddings
  • anchored claddings

Up to 0.1 m2 Individual size tiles can be mortared or moved using the thin bed method. In addition, the panels must be anchored individually.

Since there is an increased risk with external facades, the ATV DIN 18352 also refers to the standards listed.


Since joints are an essential component in all areas of application for slab and tile work, they are dealt with separately at this point.

Mineral joints or panel joints must be able to accommodate deviations in the building materials as well as changes in length in the components. They are therefore to be created professionally in the appropriate width. According to the VOB / C standard, they should also be laid out equally wide, which contradicts the aforementioned. In order to obtain a visually appealing joint pattern, the tiles should therefore only have larger building material tolerances in isolated cases.

Movement joints are used as building separation joints, field delimitation joints as well as edge and connection joints. Their function is to enable tension-free movements of the construction. They must therefore be dimensioned appropriately and professionally.

Joint widths

The layout of the joint grid should be matched to the nominal size or the work size of the coverings. Since precise dimensions cannot be achieved in terms of manufacturing technology, the covering materials may vary within specified tolerances. The width of the joint must be created accordingly.

According to ATV DIN 18352 tile and slab work, section 3.4.1, joints serve to accommodate the tolerances of the materials. The joint widths depend on the formats of the boards and the type of board, but also on the intended use.

Assessment of joints

When assessing a joint that has been made, two adjacent workpieces or components must always be assumed. Since DIN 18352 requires the joints to be of the same width, the theoretically permissible dimensional tolerances cannot be fully exploited. If the appearance of a facade, floor covering or wall cladding as a whole or in exposed areas is impaired by strongly uneven joint widths, this is at least to be assessed as a visual defect.

Joint compensation with positive limit dimensions

The compensation of the respective material tolerances in the area of ​​the joints causes a constriction of the joint course for tiles whose size is above the respective nominal size or work size. Since such constrictions are particularly noticeable in the case of components with very large linear expansions, it is important to ensure that the existing dimensional tolerances of the individual tiles are divided between two adjacent joints.

Fig. 1: Joint system for panels with positive limit dimensions

Joint compensation with negative limit dimensions

When creating joints in connection with tiles that have a negative limit dimension, the same procedure should be followed as for tiles with positive limit dimensions. Here, too, the existing tolerance must be evenly distributed over the adjacent joints.

Fig. 2: Joint system for panels with negative limit dimensions