Method Statement for Manual Internal Plastering using High-Adhesion Gypsum Mixtures

The technology card is applicable for high-quality plastering on base structures (cast-in-place concrete class C20/25 and higher, brickwork, cellular concretes) in premises with dry and normal humidity conditions. Physicochemical parameters of the applied basic dry gypsum mixtures: bulk density is 1000-1250 kg/m³, density of the finished hardened mortar is about 1000 kg/m³. The yield of the mortar mixture is approximately 1-1.2 L per 1 kg of dry mixture. The pot life is strictly limited to 20-25 minutes.

Execution of work is permitted exclusively when a stable temperature and humidity contour is ensured. The ambient and surface temperatures must be at least +10 °C, and the relative air humidity must not exceed 60%. Prior to plastering operations, all general construction works must be completed, the building envelope must be sealed (glazing of window sashes installed), junction units sealed, and heating, water supply, and power supply systems connected (excluding the installation of finished floors).

The work is performed by a specialized team of three workers (plasterers of the 3rd, 4th, and 5th qualification grades) who have undergone specialized training. The estimated unit of final output in this card is taken as 100 m² of plastered surface. The standard labor input is 66 man-hours for stone/brick surfaces and 46.9 man-hours for concrete substrates.

1. Ensure the building's thermal envelope is closed (installation of windows, doors).
2. Connect temporary or permanent utility networks (water, electricity, heating).
3. Check the temperature regime (≥ +10 °C) and humidity (≤ 60%) using a thermohygrometer.
4. Provide the team with the necessary stainless steel tools and equipment.

The preparatory stage includes the mandatory mechanical cleaning of substrates from construction dust, cement laitance, formwork release agents, and delaminations. Protruding metal elements must be removed or treated with anti-corrosion compounds. Permissible deviations of base structures: for brickwork — no more than 10 mm vertically per story height and 20 mm horizontally per 10 m; for concrete surfaces — up to 5 mm per 1 m of length, but no more than 10 mm for the entire plane.

To ensure design adhesion (according to ISO 4624), specialized primers are used. Dense, non-absorbent concrete substrates are treated with an adhesion bonding primer containing quartz filler. Hygroscopic substrates (foam concrete, aerated concrete, ceramic brick) are coated with deep-penetrating primers. The technological break for primer layer polymerization must strictly be at least 2-3 hours.

Geodetic layout and surface plumbing are carried out using chalk line tools, laser levels, and plumb bobs. The installation of galvanized plastering beacons (standard height 6-10 mm, mass ~0.12-0.16 kg/m) is performed on a gypsum mortar mixture applied at a pitch of 300 mm. The beacon installation pitch depends on the length of the straight edge: 1700-1800 mm for a 2-meter straight edge and 1200-1300 mm for a 1.5 m straight edge. Angle bead mesh profiles are mounted in a similar manner with their ends trimmed at a 45° angle.

1. Perform mechanical cleaning and dedusting of the base surface.
2. Apply the primer compound appropriate for the substrate type using a roller or block brush.
3. Maintain a technological pause of 2-3 hours for the primer to dry completely.
4. Perform surface plumbing of the walls, install edge dowels at a distance of 30-40 cm from the corners.
5. Fix the plastering beacons on dabs of gypsum mortar, align vertically using a tape measure or a straight edge with a spirit level.

The hydration process of the dry gypsum mixture requires strict adherence to the water-to-solid (W/S) ratio. Inventory plastic containers with a volume of 90 or 200 liters are used for mixing the mortar. Clean cold water is poured into the container at a rate of approximately 18 liters per 30 kg (one standard bag) of dry mixture. The use of warm water or contaminated containers critically reduces the mortar's pot life.

The mixing process takes place in two stages to ensure uniform dispersion of polymer modifiers. Initially, 8-10 trowels of dry mixture are poured into the water and mixed for 2 minutes. Then, the remaining volume is gradually introduced under continuous mixing using a construction mixer (with a power of at least 1.2 kW). Once a homogeneous mass is achieved, the mortar is left for 5-7 minutes for the complete dissolution of chemical additives, after which the final mixing is performed.

The optimal rheology of the mortar is instrumentally controlled: the mobility of the mixture is determined by the slump of a standard cone, which should be 8-12 cm. An important technological limitation: to adjust the consistency during the initial mixing process, adding water or dry mixture is permitted; however, after the final mixing and resting period, adding dry mixture is strictly prohibited. The ready mortar must be completely used within 20-25 minutes.

1. Measure 18 liters of clean cold water into a clean plastic container (based on 30 kg of mixture).
2. Add 8-10 trowels of dry mixture, mix with a mixer for 2 minutes.
3. Pour in the rest of the bag, mix until a homogeneous state is achieved.
4. Take a technological pause of 5-7 minutes for the polymer additives to mature.
5. Perform a brief secondary mixing.
6. Check the mobility of the mortar (cone slump of 8-12 cm).

The spatial sequence of plastering is strictly regulated: ceiling surfaces → walls → window and door reveals. The mortar is applied with a wide stainless steel float or trowel. The application vector for walls is from bottom to top, for ceilings — pulling 'towards oneself'. The design thickness of a single layer is from 5 to 15 mm. If it is necessary to form a layer thicker than 15 mm, the first layer (while in a plastic state) is profiled with a plastering comb ('dovetail' shape), and the second layer is applied no earlier than after 24 hours.

The distribution and rough leveling of the mass are performed using an h-shaped aluminum straight edge with zigzag movements from beacon to beacon. Excess mixture accumulating on the working edge of the straight edge is removed with a trowel and redistributed into depression zones (hollows). Internal and external corners are formed with specialized corner trowels. Reveals are plastered with a specified slope from the window/door frame to the wall plane (splay angle), the accuracy of which is controlled by a steel square with a sliding bar.

The trimming stage begins after the primary setting of the matrix — approximately 45-70 minutes after application (when the surface no longer yields to light finger pressure). Protruding irregularities are cut off with a trapezoidal straight edge or a wide steel spatula. The formation of a precise reveal corner geometry after setting is performed with a specialized edge plane ('Kantenhobel').

1. Apply the mortar mass in a layer of 5-15 mm, observing the sequence: ceiling, walls, reveals.
2. Level the applied layer with an h-shaped aluminum straight edge using zigzag movements.
3. If a layer >15 mm is required, apply grooves ('dovetail') and leave for 24 hours before the second layer.
4. Form the splay angle on the reveals, controlling the geometry with a special square.
5. After 45-70 minutes, trim the plane using a trapezoidal straight edge.

Preparation of the plaster layer for the final finish (high-quality painting or wallpapering) is performed during the strength gain phase. 15-20 minutes after trimming with a trapezoidal straight edge, the surface is copiously moistened and sponged with a rigid sponge or felt float in circular motions. This operation extracts the gypsum laitance to the surface and levels the microrelief left after working with the straight edge.

After a characteristic matte shade appears (evaporation of surface moisture), primary smoothing is performed with a stainless steel trowel. To achieve Q3/Q4 category quality (for high-quality painting), the surface is re-moistened and smoothed tight (scraped flat) within 24 hours after setting. This method completely eliminates the need for subsequent continuous filling (puttying).

A critically important technological technique for ceiling surfaces is cutting the plaster layer to its full depth along the perimeter of the junction with the walls (performed with a plaster saw / 'Stucksäge'). This creates an expansion joint that prevents random cracking in the center of the room during shrinkage deformations. The period of full hydration and drying of a 15 mm layer is about 5 days. During this period, intensive ventilation without drafts must be ensured.

1. Maintain a pause of 15-20 minutes after trimming.
2. Copiously moisten the surface with water and sponge with a sponge float in circular motions.
3. Wait for the surface to become matte and smooth with a wide steel spatula.
4. For perfect smoothness (after 2-24 hours), re-moisten and smooth tight with a metal trowel.
5. Cut the plaster layer on the ceiling along the entire perimeter of the junction with the walls.

The quality control system is based on international standards for inspecting construction processes and includes incoming, operational, and acceptance control. During incoming control, the integrity of the packaging and the shelf life of the mixtures (no more than 3 months) are checked, as well as the geometry of metal profiles (local curvature must not exceed 2 mm per 1 linear meter). Materials must be stored on wooden pallets in dry premises.

Operational control of geometric parameters is performed using two-meter spirit levels and laser levels. Strict tolerances for high-quality plastering are: deviation from vertical and horizontal no more than 1 mm per 1 meter of length. The maximum deviation of verticality for the entire height of the room (limited by floor slabs) must not exceed 5 mm. For window and door reveals, the tolerance for vertical/horizontal deviation is 1 mm per 1 m (no more than 3 mm for the entire element), and the deviation of the reveal width from the design must not exceed 2 mm.

Instrumental control of flatness (evenness) is performed by applying a two-meter straight edge in arbitrary directions (at least 5 measurements per 50-70 m²). On an area of 4 m², no more than two smooth irregularities (depressions or bulges) with a height/depth of up to 1 mm are permitted. If defects exceeding these tolerances are detected, corrections are made with a straight edge at the pre-setting stage, and after hardening — by local sanding or additional filling.

1. Incoming control: checking the shelf life of mixtures and the straightness of profiles (curvature tolerance < 2 mm/m).
2. Operational control: measuring the slump of the mixture batch with a cone (norm 8-12 cm).
3. Instrumental geometry check: applying a 2-meter straight edge (max. 2 gaps up to 1 mm per 4 m²).
4. Checking wall verticals with a plumb bob/laser (deviation ≤ 1 mm/m, max 5 mm over the height).

The execution of plastering works is carried out in compliance with industrial safety requirements (comparable to ISO 45001 standards). Personnel at least 18 years old, who have undergone specialized safety induction and hold a Class I electrical safety qualification group for working with mechanized tools, are permitted to work. The use of personal protective equipment (PPE) — FFP2 class respirators, closed-type safety goggles, and alkali-resistant gloves — is mandatory due to fine dust and the alkaline reaction of fresh mortars.

Power tools (mixers, drills) must be connected via residual current devices (RCDs). In conditions of insufficient lighting, portable lamps with a voltage not exceeding 36V are used (in an explosion-proof design if necessary). The use of improvised supports (barrels, boxes) is strictly prohibited; for works at height, only inventory prefabricated scaffolds that have passed static tests are used.

During the cold season, when working in heated premises, it is necessary to organize forced or natural purge ventilation (at least once per working shift) to reduce the concentration of moisture and dust. Washing of plastic containers and stainless steel tools must be carried out in specially designated areas with the disposal of gypsum sediment in accordance with environmental regulations; discharging mortar residues into the combined sewer system without filtration is prohibited.

1. Perform an idle check of the electric mixer cable insulation before the shift.
2. Erect inventory scaffolds for work at heights above 1.3 meters.
3. Provide personnel with PPE (goggles, respirators, gloves).
4. Organize a tool cleaning area with a filtration settling tank for water.
5. Ensure purge ventilation of the premises at least once per shift.