Introduction to Self-Leveling Cement Floor Screed Construction
Release Time:
2015-12-28
Source:
Introduction to Self-Leveling Cement Floor Screed Construction
Before starting any renovation, it is generally necessary to conduct a comprehensive inspection of the property, with a key focus on whether the floor surface is level. If the floor slopes relative to the horizontal plane or has significant depressions and bumps, it must be leveled; otherwise, the quality of the underlayment or floor tiles will be compromised. Self-leveling screed is the most common method for leveling floors, and the following section provides a detailed explanation.
Self-leveling is currently the most commonly used method for floor leveling and delivers the best leveling results.
1. Floor grinding and treatment
The ground is in use. Self-leveling cement Before leveling, the floor must first be pre-treated. On typical bare concrete floors, there are often protrusions that need to be ground down. A floor grinder is typically used to flatten these bumps through rotary surface grinding.
2. Apply interface agent
The purpose of the primer is to ensure a stronger bond between the self-leveling cement and the substrate. After the substrate has been ground and thoroughly cleaned, two coats of primer should be applied to the smooth, leveled surface. The market offers a wide variety of primer products; homeowners should choose high-quality formulations to prevent various quality issues from arising in the finished floor later on.
3. Self-leveling cement
Self-leveling cement is a dry-mix powdered material composed of multiple active ingredients that can be mixed with water on site and immediately applied. The typical water-to-cement ratio is 1:2. It is important to ensure the mixture flows freely without being too thin; if it is too runny, the hardened material will lack sufficient strength and be prone to dusting.
After the primer has dried, the mixed self-leveling cement can be poured onto the floor. Once on the surface, the cement will flow and spread naturally, but it will not achieve complete leveling on its own; therefore, construction personnel must use a screed bar to push and smooth the material, ensuring an even, level finish.
4. Use a roller to evenly compact the cement.
Cement is not a perfectly fluid material, so it cannot achieve absolute levelness; during the spreading and leveling process, slight unevenness will inevitably occur. This is precisely when a screed roller is needed to compact and smooth the cement evenly. Omitting this step can easily result in localized unevenness on the floor, as well as issues such as small areas of delamination or hollow spots later on.
5. Construction Precautions for Self-Leveling Floor Screed
To prevent footprints from being left on the concrete during construction, workers are typically required to wear special footwear designed to minimize such marks. These shoes feature a sole studded with numerous nails, which ensures stable footing while effectively reducing the likelihood of leaving impressions on the concrete surface.
Pay attention to curing the finished product.
Self-leveling compound dries quickly; typically, wood flooring can be installed after about three days. However, during the three days before it fully dries, proper protection of the finished surface is essential.
Traditional cement mortar leveling
Although cement-sand mortar leveling has numerous drawbacks, it remains a relatively traditional leveling method; due to the slow pace of technological advancement, many renovation teams still rely on this approach.
1. Subfloor Preparation
Prior to commencement of construction, the subfloor must also be properly prepared to ensure that defects such as hollows and delaminated sections have been repaired or removed. The subfloor must be thoroughly cleaned to eliminate any obstacles to work. In addition, the bases of completed woodwork should be protected with wrapping, and the bases of existing interior fixtures should either be wrapped or shielded with appropriate materials.
2. Elevation plastering pads
The screed thickness shall be determined based on the type and thickness of the floor finishing material and the finished-surface reference line; generally, the finish-layer plastering thickness shall not be less than 20 mm, and screed control lines shall be struck on the wall surfaces. Along the perimeter of the walls, plaster pads shall be applied in accordance with the screed control lines; these pads are typically 5 cm × 5 cm in size, spaced 1.5 to 2.0 meters apart both horizontally and vertically, with their top surfaces serving as the elevation datum for the floor finish. For larger rooms, additional screed ribs shall also be provided. The mortar mix proportions for applying the plaster pads and screed ribs shall be identical to those used for the floor screed.
3. Apply cement slurry
The purpose of the cement slurry is to ensure a tighter bond between the cement-sand mortar and the substrate. The slurry should be mixed at a ratio of 1:0.5; once prepared, it is applied to the substrate using a broom or similar tool to form a bonding layer.
4. Apply cement mortar
After applying the cement mortar, spread a layer of cement mortar with a mix ratio of 1:2 (cement to sand), ensuring thorough and uniform mixing. Once the mortar is evenly spread over the entire area, compact and smooth it using a long wooden screed to ensure tight bonding between the mortar and the substrate.
5. Matte Surface Treatment
Surface troweling is carried out in two passes. The first pass is performed when the cement mortar has just begun to set and exhibits slight bleeding; footprints remain upon stepping on it, but the surface does not sink. At this stage, dry cement is sprinkled over the surface, followed by troweling with a steel trowel, working sequentially from the edges and corners to the main areas, gradually increasing pressure to compact and smooth the surface. The second pass of troweling is conducted before the cement mortar reaches final set, using the steel trowel to flatten, compact, and polish any trowel marks left from the first pass. Throughout the process, a straightedge is used at all times to check for evenness.
