Repair of a flat roof often begins with a critical stage that determines the quality of all subsequent waterproofing. Disassembling screeds on the roof is not just the removal of old concrete, but a complex engineering task that requires accurate load calculation and understanding of the structure of the roofing pie. Errors at this stage can lead to damage to the load-bearing structures or the need for expensive repair of the flooring plates.
During operation, the cement-sand layer (CPS) accumulates moisture, loses adhesion and cracks, ceasing to perform its function of leveling and distribution of loads. If you are planning a complete roof renovation, dismantling This is a necessary step to ensure the longevity of the new system. Ignoring base defects will negate even the highest quality waterproofing materials.
In this article, we will discuss in detail the methods of removing the concrete layer, the necessary tools and safety rules. You will learn how to minimize dust and noise, properly organize the logistics of garbage descent and prepare the ideal base for the new project. roof-carpet. Competent approach will save the budget and avoid unforeseen situations in the process of work.
Diagnostics of the condition of the old coating
Before picking up a punch or ordering heavy equipment, it is necessary to conduct a thorough examination of the current surface. Visual inspection is often insufficient, as the outer cracks may be just the tip of the iceberg. Professional defect allows you to assess the real strength of the screed and the degree of its moisture. Often, the top layer looks normal, but underneath it hides completely destroyed material.
For an accurate assessment of humidity, special devices are used - moisture meters, which show the percentage of water content in concrete. High humidity (more than 4%) requires mandatory drying or complete removal of the layer, as sealed moisture under the new waterproofing will boil in the summer and break the coating. Also checked adhesion to the base by tapping: a deaf sound indicates detachment.
⚠️ If more than 30% of the area is knocked out, local repair is impossible – a full sound is required. screed-up All over the roof.
The results of the diagnosis directly affect the choice of dismantling technology. If the screed is strong but just old, diamond cutting may be required. If the material crumbles into a crumb, a more gentle mechanical method will be suitable. It is also important to identify hidden communications or rebars that may complicate the process.
Choice of dismantling technology: mechanics or hydraulics
There are two main approaches to removing the concrete layer: mechanical and hydraulic. The mechanical method involves the use of jackhammers, punches and hydrohammers. This is the most common method to quickly break concrete into fragments. However, it puts a huge strain on the floors and generates a lot of dust, which requires additional protection measures.
The hydraulic method (hydro demolition) is more modern and gentle. Special high-pressure installations supply water that knocks out cement milk, leaving the rebar and solid base intact. This method is ideal for cases where it is necessary to preserve the load-bearing capacity of the plates or remove only damaged areas. In addition, the water immediately washes away dust, which is critical for working in residential areas.
When choosing equipment, the thickness of the layer should be considered. For a thin screed up to 5 cm, powerful punches with peaks are enough. If the thickness exceeds 10 cm or the concrete is reinforced with a double mesh, it will be required hydrohammer Or even a small excavator with attachments. It is important not to damage the insulation layer under the screed, if it is to be preserved.
Equipment and protective equipment required
High-quality disassembly of screeds on the roof is impossible without the right tool. The basic set includes SDS-Max punches, jackhammers (pneumatic or electric), scraps, picks and shovels. For cutting concrete into squares is often used benzoresis or electric stroboresis with diamond discs with a diameter of 350 mm.
Particular attention should be paid to personal protective equipment (PPE). Concrete dust contains silicon, which is harmful to the lungs, so having FFP2 or FFP3 class respirators is a must. It will also be necessary:
- 👷 Safety glasses with side protection from flying fragments
- 🧤 Vibroprotective gloves for working with breakers
- 👟 Special shoes with reinforced sock and sole resistant to punctures
- 🎧 Building headphones or earplugs to protect hearing
To lift equipment on the roof and descent of garbage often use freight elevators or cranes-manipulators. If access is restricted, temporary gutters are arranged or Big Bag building bags are used, which are descended by a winch. Logistics planning is a key factor in success.
Step-by-step instructions for removing the screed
The dismantling process must be strictly regulated to avoid chaos and injury. First, the surface is marked into squares about 50x50 cm or 60x60 cm in size. This facilitates the subsequent collection and disposal of waste. Then the sleeves are cut to the depth of the screed.
☑️ Checklist for preparation for dismantling
After cutting the cards, the direct crushing of concrete begins. Work is carried on from centre to edge or from one corner to another, so as not to obstruct the movement of the workers. The broken pieces are immediately loaded into bags or wheelbarrows. Do not accumulate a large amount of garbage in one area, so as not to exceed the permissible load on the overlap.
The final stage is the cleaning of the base. The remnants of concrete are slammed down to the floor slab. If the project provides for the device of a new screed on the lighthouses, the surface should be dusted with an industrial vacuum cleaner. Deep potholes in the plates are sealed with repair compounds.
⚠️ Warning: When working with a punch, hold the tool with both hands and monitor the position of the body. A sharp departure of the drill into the void can lead to loss of control and injury.
It is important to control the process so as not to damage the joints of the plates or not to break through the waterproofing of the underlying floors (if the dismantling does not go to the plate). In case of detection of the valve, it is cut off with a Bulgarian or snacked with hydraulic scissors.
Works and logistics of garbage
The most difficult part of the process is often not the breaking of concrete itself, but the organization of the removal of tons of construction debris. The weight of a cubic meter of concrete crumb can reach 2400 kg. For a standard roof of 500 square meters with a screed thickness of 5 cm, the garbage volume will be 25 cubic meters, which will require several dump truck flights.
To optimize the process, special garbage conduits are used, if the height of the building allows, or temporary stingrays are organized. In dense urban areas, it may be necessary to install protective screens or visors over the entrances to the building. Disposal of garbage should be as it accumulates, without cluttering the work areas.
| Type of equipment | Performance (m2/hour) | Noise level | Dust formation |
|---|---|---|---|
| Puncture (manual) | 1-2 | High-pitched | High. |
| The jackhammer | 3-5 | Very tall. | High. |
| Hydrohammer (on the excavator) | 10-15 | Medium. | Low (with water) |
| Hydraulic cutting | 5-8 | Low. | Minimum |
Effective planning reduces downtime of machinery and workers. Pre-ordered containers and agreed export routes are a guarantee of meeting the deadlines.
Safety and environmental standards
Working at height and with heavy tools requires strict compliance with labor protection rules. All workers must be instructed and allowed to work at height. The use of safety tethers is mandatory if the work is carried out at the edge of the roof without fences. Windy weather can be a limiting factor for lifting cargo.
The environmental aspect is also important: concrete dust should not be spread by wind in the area. It is recommended to use dust suppression systems or moisten the surface before starting work. Noise work in residential areas is allowed only at certain times of the day, usually from 9:00 to 19:00, which should be taken into account when planning the schedule.
What do we do with the rebar?
The old rebar net left after dismantling the screed cannot be simply thrown into the trash. It must be collected, cut into convenient bars and handed over to scrap metal reception points. This is not only an environmental requirement, but also a way to partially offset the costs of concrete disposal.
Don't forget about fire safety. Sparks from Bulgarians or benzoresis can ignite bitumen residues or dry grass if it hits the roof. The presence of fire extinguishers and buckets of sand in the workplace is a mandatory requirement.
Preparation of the basis for new work
After the old screed is completely removed, the “skeleton” of the roof opens. The surface should be flat, dry and clean. Any oil stains, bitumen residues or glue are removed mechanically or chemically. Only on the prepared basis can a new application be made primer And then we put a sloping layer in.
If in the process of dismantling were found defects of plates (cracks, through holes), they are subject to mandatory repair using special repair mixtures on a cement basis. Ignoring these defects will lead to leaks in the future, regardless of the quality of the new waterproofing.
Use the laser level to check the base plane after dismantling. Elevation differences of more than 5 mm by 2 meters of linear require alignment before laying vapor isolation.
High-quality disassembly of screeds on the roof is the foundation for a reliable roof. Savings at this stage or negligence in the preparation of the base will inevitably lead to a reduction in the service life of the entire roofing.
Can I remove the screed without damaging the thermal insulation?
It's possible, but it's difficult. Requires the use of gentle methods, such as diamond cutting to the depth of the screed and careful removal of plates. However, if the thermal insulation (for example, polystyrene foam) was glued or filled with a solution, most likely, it will have to be changed completely.
How much does a new screed dry before putting waterproofing?
The drying time depends on the thickness of the layer, temperature and humidity of the air. On average, cement-sand screeds take 28 days to gain strength and dry completely. The use of quick-drying additives can reduce this period to 7-14 days.
Do I need to make deformation seams with a new screed?
Yes, I will. Deformation seams compensate for the temperature expansion of concrete and prevent the formation of chaotic cracks. They should coincide with the seams in the floor plates and be located in increments of no more than 6 meters.
What is the minimum slope should be at the screed?
According to the building codes, the minimum slope for flat roofing should be 1.5-2% (1.5-2 cm per 1 meter linear) to ensure effective drainage and prevent the formation of puddles.