🏗️ Masonry units — flatness of surfaces: measurement of the length of both diagonals with a graduated straight edge (0.5 mm) and of the greatest distance of the surface from the straight edge on each diagonal with a feeler gauge (0.05 mm), concave and convex surfaces; at least 6 units (3 for the flatness of bed faces); PN-EN 772-20

Construction PN-EN 772-20

Overview

WHAT THE STANDARD COVERS. According to clause 1 of EN 772-20:2000 the standard specified a method for determining the flatness of faces of aggregate concrete, manufactured stone and natural stone masonry units; amendment EN 772-20:2000/A1:2005 deleted the listed types of units from the title and scope — after the amendment the scope reads: a method for determining the flatness of surfaces of masonry units. "Scope" field of the PKN card for PN-EN 772-20:2002 (Polish version): "A method for determining the flatness of faces of aggregate concrete, manufactured stone and natural stone masonry units is specified. The apparatus is specified, and the preparation of specimens, the performance of the test and the calculation of results are given". PKN card for amendment PN-EN 772-20:2002/A1:2005 (English version) — "Scope": an amendment to the title and to the scope, normative references and clauses 4.1, 5, 6.1, 6.2 and 7.

ACCORDING TO THE TEXT OF EN 772-20:2000 AND AMENDMENT A1:2005 — APPARATUS, SPECIMENS, PROCEDURE, RESULTS (forewords, clauses 1–7, modifications 1–8). The standard was prepared by CEN/TC 125 (Masonry; secretariat BSI); national implementation at the latest by September 2000; amendment A1 — at the latest by August 2005. Normative references (after A1): EN 771-1, 771-2 and 771-4 undated and EN 771-3, 771-5 and 771-6 (specifications for masonry units). Apparatus (clause 3): a graduated straight edge longer than the diagonals of the long faces of the unit being tested; a set of feeler gauges capable of measuring with an accuracy to 0.05 mm. Sampling (4.1): the method of sampling is stated in the test report; the minimum number of specimens is six, except for the determination of flatness of bed faces, where it is three (A1); the product specification may require a larger number, in which case the larger number is used. Preparation (4.2): material adhering to the unit as a result of manufacture is removed before measuring. Procedure (clause 5 as worded by A1): 5.1 — the unit is positioned in a stable manner; for each surface specified as plane the procedures in 5.2 and 5.3 are followed, and for units suitable for thin layer masonry the procedure in 5.3 is carried out on each bed face; 5.2 — for each plane surface the length of both diagonals is measured with the straight edge to the nearest 0.5 mm; 5.3 — the straight edge is placed across each diagonal in turn and the distance from the surface to the straight edge is measured with the feeler gauge; for a concave surface — the greatest distance to the nearest 0.05 mm; for a convex surface the straight edge is placed so that the greatest distances on either side of the point of contact are approximately equal, and both are measured to the nearest 0.05 mm. Calculation (6.1 after A1): for each plane surface the mean length of the diagonal is calculated; for a concave surface the mean deviation from flatness is the mean of the maximum distances on both diagonals; for a convex surface the mean of the maximum distances is calculated for each diagonal and then the mean of these two results. Expression (6.2 after A1): 6.2.1 — for plane surfaces the mean length of the diagonal to the nearest millimetre and the mean maximum deviation from flatness to the nearest 0.1 mm; 6.2.2 — for bed faces the maximum deviation from flatness to 0.1 mm and the mean maximum deviation to 0.1 mm. Test report (clause 7 after A1): among others the type, origin and designation of the unit by reference to the relevant part of EN 771; the number of specimens; the lengths of the individual diagonals and the mean (to 1 mm) for each plane surface; the maximum distance from the straight edge on each diagonal and the mean deviation (to 0.1 mm); for bed faces of units for thin layer masonry — the maximum distances on each diagonal, the flatness of the bed faces being the largest individual value from the sample (to 0.1 mm); whether the surface is concave, convex or of another configuration.

STATUS (PKN cards as of 10.11.2026). The card for PN-EN 772-20:2002 (Polish version) has no withdrawal label: published 19-08-2002, 7 pages, KT 233 for Masonry Structures, "Implements: EN 772-20:2000 [IDT]", ICS 91.080.30, 91.100.15, 91.100.30. The card for PN-EN 772-20:2002/A1:2005 (English version) has no withdrawal label: published 15-11-2005, 5 pages, "Implements: EN 772-20:2000/A1:2005 [IDT]". The PKN search (query "PN-EN 772-20", 10.11.2026) shows only these cards and the card of the amendment in the German version — there is no Polish version of amendment A1. iTeh catalogue (read 10.11.2026): EN 772-20:2000/A1:2005 — CEN/TC 125, published 09.02.2005, stage 6060.

HOW MANY LABORATORIES AND IN WHAT FORM (accreditation scope database of the service and the "Laboratories" tab on labcoda.pl, read 10.11.2026). The notation 772-20 appears in 7 records at 5 Polish laboratories: AB 251 (2 — sand-lime and clay masonry units: "PN-EN 772-20:2002 | PN-EN 772-20:2002/A1:2005"), AB 054 (2 — aggregate concrete masonry units, autoclaved aerated concrete precast elements: "PN-EN 772-20:2002+A1:2005"), AB 011 (1 — masonry units), AB 687 (1 — clay masonry units) and AB 023 (1 — masonry units, including autoclaved aerated concrete, sand-lime and clay units: "PN-EN 772-20"). Outside Poland — 10 records at 6 Czech laboratories (1007.1, 1018.3 — 4 records, 1046, 1234 — 2, 1396, 1778: "ČSN EN 772-20", in 1778 also "STN EN 772-20"). The "Laboratories" tab ("PN-EN 772-20") shows 11 laboratories (5 PL, 6 CZ) and 17 items. We have not compared the current PCA scope documents of these laboratories with the database.

WHAT THE LABORATORIES TEST (scope database, complete items — 7 Polish). AB 011 — masonry units: flatness of faces. AB 687 — clay masonry units: flatness of faces. AB 251 — sand-lime and clay masonry units: flatness of surfaces. AB 054 — aggregate concrete masonry units (external appearance) and autoclaved aerated concrete precast elements (flatness of surfaces). AB 023 — masonry units, including autoclaved aerated concrete, sand-lime and clay units: flatness of faces. The text of EN 772-20:2000 did not list clay, sand-lime or aerated concrete units — after amendment A1 the scope covers masonry units without listing types.

WHERE AN APPARENTLY CORRECT RESULT IS EASY TO GET. Specimen: fewer than 6 units (or fewer than 3 for bed faces) or fewer than the product specification requires; measurement without removing material adhering after manufacture; a unit positioned unstably. Measurement: a straight edge shorter than the diagonal; on a convex surface the straight edge has to be positioned so that the distances on either side of the point of contact are approximately equal, and both measured — a single measurement with a tilted straight edge gives a different deviation; feeler gauge accuracy 0.05 mm, diagonal length 0.5 mm. Calculation: for plane surfaces the MEAN deviation is given (from two diagonals, for a convex surface — from four readings in two steps), and for bed faces of units for thin layer masonry — the largest individual value from the sample; rounding to 0.1 mm and the diagonal length to 1 mm. Edition: the text before A1 did not provide for determining the flatness of bed faces and always required 6 specimens — comparing results without stating whether A1 was applied mixes two sets of rules.

WHAT WE DO NOT GIVE. Parts read: the iTeh sample of SIST EN 772-20:2000 (EN 772-20:2000, full text — a scan read from page images) and the iTeh sample of SIST EN 772-20:2000/A1:2005 (full text of amendment A1). We do not give flatness requirements for masonry units or categories of deviations — they are given in the parts of EN 771, which we have not read. We have not checked the status of the EN 771 standards. PKN has not issued the designation "PN-EN 772-20:2002+A1:2005" used in the scopes as a separate standard (the search shows the standard and the amendment separately).

Method principle

On each surface of a masonry unit specified as being plane the length of both diagonals is measured with a graduated straight edge (0.5 mm), and then, placing the straight edge across each diagonal in turn, the greatest distance of the surface from the straight edge with a feeler gauge (0.05 mm) — for a convex surface on either side of the point of contact; the result is the mean length of the diagonal (1 mm) and the mean maximum deviation from flatness (0.1 mm), and for bed faces of units for thin layer masonry — the maximum deviation (EN 772-20:2000 with A1:2005, clauses 3–6).

Applications

• Masonry units — surfaces specified as being plane (EN 772-20:2000/A1:2005, amended scope)
• Bed faces of units intended for thin layer masonry (A1, 5.1 and 6.2.2)
• Test method for units covered by the EN 771 specifications (normative references)
• In accreditation scopes: 5 Polish laboratories — clay, sand-lime, aggregate concrete and autoclaved aerated concrete masonry units

Key parameters

Standard

Standard number

PN-EN 772-20:2002 (Polish version; implements EN 772-20:2000 [IDT]) with amendment PN-EN 772-20:2002/A1:2005 (English version; implements EN 772-20:2000/A1:2005 [IDT])

Title (PL)

Metody badań elementów murowych — Część 20: Oznaczanie płaskości powierzchni licowych elementów murowych

Title (EN)

Methods of test for masonry units — Part 20: Determination of flatness of faces of masonry units

Step-by-step procedure

1. Specimens

   At least 6 units (3 for the flatness of bed faces), method of sampling in the test report; removal of material adhering after manufacture (4.1–4.2 after A1).

2. Positioning

   Unit positioned stably; surfaces specified as being plane and — for units for thin layer masonry — bed faces identified (5.1 after A1).

3. Diagonals

   Length of both diagonals of each plane surface with the graduated straight edge, to 0.5 mm (5.2 after A1).

4. Deviation from flatness

   Straight edge across each diagonal in turn, distance from the surface with a feeler gauge: concave — the greatest; convex — both on either side of the point of contact with the straight edge balanced; to 0.05 mm (5.3 after A1).

5. Result and test report

   Mean diagonal length (1 mm) and mean maximum deviation (0.1 mm); bed faces — maximum deviation (0.1 mm); shape of the surface in the report (6.1–7 after A1). PN-EN 772-20:2002 with A1:2005 — current (PKN cards as of 10.11.2026).

Required equipment and apparatus

Health and safety (OHS)

• Carrying and positioning heavy masonry units — stable base, protection of hands and feet
• The standard gives no hazards of the test — NOT GIVEN
• TECHNICAL NOTE: flatness requirements are given in the parts of EN 771, not in EN 772-20; results from the text before A1 and after A1 are not directly comparable

Frequently asked questions