MASONRY AND PLASTER WORK

1 Masonry and plaster work

1.1 Scope

This Specification covers the requirements for masonry work and plaster work.

1.2 Masonry work

1.2.1 Materials

1.2.1.1 Bricks and blocks

Bricks shall be clay facing bricks manufactured locally. The quality shall correspond to DIN 105. Blocks shall be dense concrete blocks to DIN 18153 with a compressive strength of > 7.5 N/mm². Bricks and blocks shall be hard, sound, square and clean with sharp well defined arises. The Contractor shall submit samples of each type of brick and block and obtain approval before placing orders with suppliers.
Strength test certificates performed on the basis of appropriate DIN standards for all bricks and blocks shall also be submitted to the Engineer.

1.2.1.2 Reinforcement

Reinforcement for brickwork shall be in accordance with DIN 488, DIN 1045 and DIN 1053. Reinforcement for brickwork shall be Type I G or Type III U standard. Reinforcement shall be detailed, stored and tested as specified under ‘Reinforcement for concrete.’

1.2.1.3 Fixings

Stainless steel for sheet, strip, plate and bars shall be '1.4302 E 23 quality to DIN 17440.

1.2.1.4 Sand, Cement, Water

Sand shall be clean and sharp coarse grit, fresh water river or pit sand conforming in all respects to DIN 1053 and DIN 18550 and shall be re-washed in site if the silt loam or clay content exceeds the requirements described in DIN 4226. The sand shall be obtained from a source approved by the Engineer. Cement shall be sulphate resisting Portland cement as specified in DIN 1164.
Water shall be clean and free from impurities and shall at regular intervals be tested to ensure compli-ance with DIN 4030 and DIN 38404.

1.2.1.5 Mortar Mix

Masonry mortar for setting blocks and bricks shall be of the quality of Group III according to DIN 18550. The proportion shall be 1 part cement to 4 parts sand or as otherwise approved by the Engineer. Mortar shall be mixed with water in an amount compatible with workability. Mortar constituents shall be measured by volume, using clean gauge boxes made to size to suit volumes required. Gauge boxes shall be overfilled and excess material struck off with a straight edge.
Mortar shall be mixed in a mechanically operated mortar mixer for at least three minutes after all ingredients are in the drum, and at least long enough to make a thorough, complete, intimate mix of the materials.
The mixing of mortar by hand will be permitted only when the quality of hand mixing is comparable to mechanical mixing. The Engineer reserves the right to reject hand mixing and require all mixing to be by mechanical means.
Mortar shall be used within two hours of discharge from the mixer at normal temperature and on no account shall mortar be used after the initial set has taken place. Reconstitution of mortar will not be permitted. Mortar boxes shall be cleaned out at the end of each day and all tools shall be kept clean. Coloured mortar shall be mixed as specified using cement and sand in the above proportions with the addition ===Workmanship===

1.2.1.6 General

All masonry shall be laid plumb and true to lines and built to the thickness and bond required with courses level and joints and bond uniform. Masonry shall be carried up in a uniform manner. No one portion shall be raised more than a meter above adjacent portions, except with the approval of the Engineer. Sample panels 1 m2 shall be prepared for each type of facing brickwork/blockwork, including jointing or pointing, and the Contractor shall obtain approval before proceeding with the work.
Hot weather: Bricks and blocks shall be stacked on a level hardstanding so as to prevent the absorption or ingress of water. Suitable shading shall be provided to prevent high temperatures existing within the brick and block stacks.
Dry weather: Clay brickwork and blockwork shall be kept wet to the minimum extent necessary to prevent mortar drying out prematurely.
Wet weather: Freshly laid brickwork/blockwork shall be protected during interruption through rain and at the completion of each day's work.
Facework shall be kept clean during construction and until practical completion. Scaffold boards shall be kept clear of the building at night and during heavy rain. Rubbing to remove stains will not be permitted. All bricks shall be wetted before being laid.
Clay bricks shall not be used until completely cold from the kiln.
Facing bricks of varying colour shall be distributed evenly throughout the work so that no patches appear.
Different deliveries which vary in colour shall be mixed to avoid horizontal stripes. Brickwork shall be carried up, including both skins of cavity work where applicable, with no portion more than 1.5 m above another at any time, racking back between levels.
Brickwork shall be gauged for four courses to 300 mm including joints.
Bricks shall be laid on a full bed of mortar and all joints filled. Bed and vertical joints shall be of equal and consistent thickness.
Solid bricks shall be laid on a full bed of mortar with joints filled solid to a consistent thickness not more than 12 mm.
Should single frogged bricks be permitted, they shall be laid with the frog upwards and these shall be filled with mortar. Double frogged bricks shall not be used.
Courses shall be kept level and perpends vertical and in line. Quoins and other angles shall be plumbed as the work proceeds.
Templates shall be used for forming openings in face work where doors and windows are not built in at the time.
Brickwork and blockwork abutting concrete columns, walls and beams shall be tied with stainless steel ties in accordance with the relevant references and as directed by the design. Additional ties shall be supplied at openings. Walls which are to be fair face shall have selected bricks and blocks with perfect arises and flat surfaces and with faces in line.

1.2.1.7 Bonding

Where not otherwise required, bricks throughout the work shall be laid with the cross joints in any course not less than a quarter of a brick from those in the course below. All brick and blockwork shall be laid in a regular pattern to the satisfaction of the Engineer.

1.2.1.8 Exposed Concrete Block

Concrete block shall be laid in "stack" bond, unless otherwise indicated, with joints not exceeding 1.0 cm and uniform throughout and finished slightly concave and smooth, tool dense and neat (no finger pointing allowed). All blocks shall be laid in a full bed of mortar applied to shells only. Mortar shall be applied to the vertical joint of blocks already set in the wall and all contact faces of the unit to be set. Each unit shall be placed and shoved against the block previously laid so as to produce a well-compacted vertical mortar joint for the full shell thickness. Moisture contents of blocks shall not exceed 35 % when laid. Intersection bearing walls shall be tied together with metal ties at one meter vertical spacing. Bends of tie bars and reinforcing shall be embedded in cells filled with mortar. Where indicated, concrete blocks shall be reinforced and concrete block lintel types shall be built in
. All necessary block cutting shall be neatly done by saws.
Control joints shall be installed at the intersection of block walls with structural concrete and elsewhere where such joints are useful. Joints not detailed otherwise shall be raked out to a depth of 2 cm for the full height of the wall and caulked. Maximum length between joints shall be 10 m.
Joints are to be examined to locate cracks, holes or other defects and all such defects shall be filled with mortar and pointed.

1.2.1.9 Concrete Blocks to be Plastered

Concrete block walls to be plastered may be laid with bonds described above. Joints are to be left rough to assist in bounding of plaster. Otherwise, concrete block masonry shall conform to previous paragraph "Exposed concrete block". Control joints in plastered block walls shall be carried through the plaster. The joint shall not be plastered.

1.2.1.10 Brickwork

Solid brick shall be laid in common bond with all joints filled solidly with mortar and backs fully purged to form solid masonry structures. Joints of walls to receive plaster shall be lightly raked to provide a bond for plaster. Solid brick shall be plastered only when so indicated on the approved drawings or required in the particular specifications.
Otherwise brickwork masonry shall conform to the paragraph 4.2.2.3 "Exposed concrete block". Control joints in plastered brick walls shall be carried through the plaster. The joint shall not be plastered.

1.2.1.11 Lintels, Ties, Miscellaneous

The Contractor shall build in or provide all miscellaneous items to be set in masonry including frames, lintels, reinforcing steel, electrical boxes and fixtures, sleeves, grilles, anchors and other miscellaneous items. All anchorage, attachments and bonding devices shall be set so as to prevent stoppage and shall be completely covered with mortar.
Wired butterfly and double triangle type wall ties will not be permitted in any wall. Wall ties shall be stainless steel strip, but of a twist type for the leaves of any cavity walls.
Padstones shall be bedded in mortar of the same strength as the adjacent wall, to give a level top surface.

1.2.1.12 Grouting

Grout and cement mortar for setting structural steel columns, railings, frames in walls and where otherwise required shall be done with mortar as hereinbefore specified. Before placing grout thoroughly clean all surfaces.
Grout shall be tamped into place with a blunt tool to fill the entire void. In the event space does not permit tamping, the Contractor shall build the necessary forms and place grout by pouring from one side only. When grout is placed by pouring a head of grout shall be maintained in the form. Grout shall be kept wet for three days and after the temporary supports adjusting wedges are removed the empty space shall be grouted and the surrounding grout pointed.

1.2.1.13 Cleaning

Masonry work, to be exposed, shall be thoroughly cleaned. Mortar smears and droppings on concrete block walls shall be dry before removal with a trowel. Masonry work may be cleaned using a mild muriatic acid solution.

1.2.1.14 Damp-proof Courses

As a minimum requirement, damp-proof courses shall be in accordance with DIN 4117 and DIN 4122. Bituminous sheet damp-proof courses shall be laid on a level bed of cement mortar with a minimum lap of 75 mm at angles and joints and neatly pointed in matching mortar on exposed edges. Horizontal and sloping damp-proof coursing over door openings shall be in single pieces of material of a length to extend 225 mm at both sides beyond the width of the frame.

1.2.1.15 Waterproof Building Paper

Waterproof building paper shall be laid beneath structural concrete. The paper shall be laid with 150 mm lapped joints which shall be treated and sealed with an approved bituminous solution. The weight of the paper shall not be less than 0.3 kg/m².

1.2.1.16 Measurement for Payment

Not used

1.3 Rendering and Plastering

1.3.1 General

The work required under this Specification shall include all labour, materials, equipment, scaffolding etc., required to complete all internal and external pl
astering specified herein.
On completion, all surfaces shall be left in a neat and clean condition before handing over
. Materials, workmanship and construction shall be in accordance with the requirements of DIN 18550.
Work shall not be started or continued when the air temperature exceeds 400C.

1.3.2 Materials

Sand shall be clean and sharp course grit, fresh water river or pit sand conforming in all respects to DIN 1053 and DIN 18550 and shall be re-washed on site if the silt loam or clay content exceeds the requirements described in DIN 4226. The sand shall be obtained from a source approved by the Engineer.
Cement shall be sulphate resisting Portland cement as specified in DIN 1164.
Water shall be clean and free from impurities and shall at regular intervals be tested to ensure compliance with DIN 4030 and DIN 38404.

1.3.3 Mixing

Plaster shall be mixed with proportions according to DIN 18550.
Plaster shall be mixed with water in an amount compatible with workability.
Plaster constituents shall be measured by volume.
Plaster shall be mixed in a mechanically operated plaster mixer at least long enough to make a thorough, complete, intimate mix of the materials.

The mixing of plaster by hand shall not be permitted. Bunkers, gauge boxes, gauging boards, etc. shall be thoroughly cleaned after each mix. Mixer drums shall be thoroughly washed out at least four times a day if the mixer is in continuous use, and after each batch if not in continuous use. All tools shall be kept clean, and care taken to ensure that fresh plaster is not contaminated with set plaster.

1.3.4 Preparation

Surfaces that are to receive plaster shall be carefully examined by the Contractor and any unsatisfactory surface shall be repaired as directed by the Engineer.

Where finished surfaces such as tile, lighting or other fixtures have been installed prior to plastering they shall be protected from damage during plastering. Protection shall consist of covering with a nonstaining building paper or polyethylene sheet. Protection shall be removed when plaster work is completed. Concrete masonry and brick surfaces shall have sufficient roughness to provide proper bond and shall be dampened by brushing or spraying with water followed by plastering.

1.3.5 Finish

Finishing coats shall be trowelled to a smooth and even finish.

1.3.6 Tolerances

All surfaces shall be true to line, level, plumb and all junctions, angles and arises truly square. On two or three coat work, the plaster surface shall not show any deviation greater than specified in DIN 1 8202 for accuracy class B.

1.3.7 Connection of Work

Completion of work shall be as follows:
Curing:
Cement sand plasters shall be kept moist by sprinkling with water at regular intervals for a period of at least three days and until no powdery particles are present.

The Contractor shall plan his work such that rendering and plastering work is not carried out at extreme temperatures.
Defects:
Work shall be free of all defects, and any work which shows signs of blistering, bond failure, hollow patches, flaking, peeling, cracking, crazing, grinning, tool marks, discolouration or any other defects will not be accepted, and shall be removed and replaced with acceptable work. Upon completion of the work, all plaster surfaces shall be cleaned and all rubbish, debris and excess material and equipment shall be removed.

1.3.8 Thickness and Workmanship

All plaster shall be applied according to the following thicknesses. Additional thickness will be required for any unevenness in the masonry surface.

Location Thickness of Coat (mm) Total Thickness
First Intermediate Finish
Ceiling 15 - 10 25
Interior Wall 10 6 4 20
Exterior Wall 10 9 6 25

Plaster shall be of two or three coats: first, intermediate and finish coats. If plaster is to be applied to a smooth cement or other surface which does not offer bonding characteristics for plaster, a dash coat shall be required as a bonding surface.

Dash coats shall be of mush consistency, composed of 1 part Portland cement and 1.5 parts of sand. The dash coat shall be applied with a whisk broom or fibre brush, in a whipping manner. The dash coat shall be kept moist for 48 hours before first coat is applied to the dash coat.

First coats shall cover the full length of the wall or to the border line formed by columns, doors and windows. Before the first coat hardens the surface shall be scratched to provide a mechanical key for the intermediate coat. This coat shall be kept moist for not less than 24 hours and allowed to set for not less than 14 days before application of the intermediate coat.

Before application of the intermediate coat, the surface of the first coat shall be dampened. The surface of the intermediate coat shall be brought to a true and even surface, then roughened with a wood float before setting to provide a bond for the finish coat.

The finishing coat shall be applied while the intermediate coat is moist and if the intermediate coat dries out it shall be wetted evenly. The finishing coat shall be first floated to a true and even surface, then trowelled in a manner that the sand particles are not exposed on the surface and with the final troweling, leaving the surface burnished smoothly and free from rough areas, trowel marks, checks, or other blemishes. Before applying the plaster to ceilings, the surface of the ceiling shall be dampened and the cement paste applied with a whisk broom or fibre brush, to the entire ceiling.

The final plaster layer shall be applied to the ceiling slab tamping it with wood float until the cement paste is squeezed up through the surface of the plaster and finally troweled to an even surface leaving the surface burnished smoothly and free from trowel marks, checks and other blemishes.

1.3.9 Waterproof

Waterproof plaster shall consist of plaster water¬proofing compound, cement and sand mixed in strict accordance with the manufacturer's specification. Waterproofing compound shall be paste, powder or liquid made by a manufacturer engaged in the mass production of such items and shall be approved by the Engineer.

1.3.10 Measurement for Payment

Not used.