What are the types of concrete screeds, the rules for preparing the base before laying the mortar, the procedure for determining the zero level and installing beacons, calculation of materials and instructions for installing a concrete floor.
Determination of the zero level of the subfloor
To keep the floor level, you need to install guides or beacons. You can fix them correctly after the zero level is determined. The appropriate tool can help you with this: a laser or a water level.
In the first case, the work will go quickly and easily. Place the laser on the floor and direct the beam to the wall. At the obtained height, for example, 140 cm, a mark is made. The laser is then transported further and a mark is made on the wall again. This must be done around the entire perimeter of the room. The resulting elevations are connected by a line.
In the case of a water level, you cannot do without an assistant. The procedure is carried out according to the following scheme:
- Pour water into a thin silicone hose.
- Make marks at both ends of the hose at the same distance.
- On the wall, mark a point at a selected distance, for example, 140 cm.
- We apply one end of the hose to the selected point. Noticing that the water level in the hose coincides with the marks on both ends, mark the second point on the wall.
- With the help of powder paint and thread, we connect the two marked points.
After the markup has been made, you can proceed to the determination of the zero level. This procedure is carried out as follows:
- We measure the height from the floor itself to the resulting line along the entire perimeter of the room. You will get different values, which is normal.
- Subtract the smallest from the largest value. This will give you the future thickness of the concrete screed. For the floor to be durable, this value should be at least 5-7 cm.
- Subtract the obtained values from the marked height. For example, we subtract 4.5 cm from the height of 140 cm.
- From the drawn line, put the resulting value down and get one more point. We do the same around the entire perimeter of the room.
- We connect the resulting points and get another line. This is the zero level. Relying on it, you can now place beacons.
Installation of beacons for concrete screed
Beacons allow you to get a flat concrete screed. For their manufacture, pipes from a T-shaped profile, special metal strips or ordinary flat rods are used. In this case, wood cannot be used because of its high ability to absorb moisture from the concrete solution. As a result, the finished screed can be deformed and skewed.
Beacons (guides) are laid parallel to the walls and perpendicular to the doors for the width of the rule increased by 10 cm. This is due to the fact that the rule should slide along them, leveling the concrete solution. 10 cm are necessary for movement in different directions along the oblique.
Place the beacons on the floor beforehand. So that they are all at the same level, it is necessary to place wooden slats on top, which must coincide with the zero level.
If somewhere the lighthouses are below, it is necessary to put a small amount of solution. You can use plastic plates, broken brick for these purposes. The use of cardboard, plywood or wood will deform the beacon (guide) due to the saturation of the substrate with moisture. They should be positioned so that the lighthouses lie flat and do not "walk".
If you plan to fill the floor in a bath or sauna, then, before making a concrete screed, you need to take care of a mandatory slope for water to drain. It must be taken into account when installing beacons and calculating the thickness of the screed.
If your concrete floor will be laid on a waterproofing film, then care must be taken when installing beacons so as not to damage the waterproofing layer.
Substrate priming procedure for concrete screed
Many consider this stage optional and skip it. However, for better adhesion of the concrete screed to the base, you need not be lazy and apply a primer. It is poured onto the prepared surface and evenly distributed around the entire perimeter of the room with a roller or large brush.
If you need to obtain certain properties, then you need to choose a primer with high waterproofing or adhesion characteristics. It is worthwhile to start laying the concrete screed only after the preliminary layer has completely dried out.
If you plan to pour on a tamped dirt floor, then there is no need to use a primer. However, the surface will need to be slightly moistened with water.
Sometimes, instead of a primer and installation of beacons, a "rough" concrete floor is poured. After it dries, a fine filling is carried out, on which leveling is performed.
Preparation of mortar for concrete screed
For a concrete screed, you can buy a ready-made solution, or you can make it yourself. For this, cement, sand, expanded clay are purchased in a hardware store. There are also ready-made dry mixes on sale.
Whatever decision you make, you need to make the correct calculation of the required material. To do this, the perimeter of the room must be multiplied by the thickness of the screed - 5-7 cm. It is not worth making it less. This is due to the fact that concrete floors tend to crack, sag, flake off. A thickness of 5-7 cm will reduce the likelihood of damage to the screed and make it as flat as possible.
If you chose a ready-made dry mixture, then it must be diluted strictly according to the attached instructions. Otherwise, you will not be able to obtain the properties specified by the manufacturer.
If you are preparing a mortar from cement and sand, then follow the following technology:
- The optimal proportion for the preparation of high-quality concrete mixture is 1 part of cement to 3 parts of refined sand. It is not recommended to use it unsifted, you can get a poor-quality solution that will quickly deteriorate.
- To improve the properties of the concrete solution, it is recommended to add expanded clay to it.
- Mix the resulting dry mixture of sand and concrete thoroughly.
- After that, take 1 liter of water for 5 kg of the mixture and, gradually pouring in, mix thoroughly with a mixer or spatula. This must be done until a homogeneous mass of one color is obtained.
- After that, leave the solution for a short time and mix thoroughly again.
- To check if the thickness is suitable, you need to take a small amount of the resulting mixture in your hand and squeeze. If you spread your palm, and there is a lump on it, then the density is suitable. You can check in one more way. We throw a small amount of the solution on the floor. If it does not spread, but simply spreads, then the mixture is ready.
When installing a concrete screed, mortars must be prepared in portions. That is why two people must work at once. While one is pouring, the second prepares the solution. This way you get a solid and uniform floor.
Features of pouring concrete solution
After all the preparatory work is completed and the solution is ready, you can start laying the mixture. We carry out the work in this order:
- We begin to lay the finished mixture from the far front corner.
- Pour the solution between the guides and level it slightly.
- Now, using the rule that is set on the lighthouses, we stretch and level the mixture. It is better to do this not in a straight line, but by moving the rule to the left and right. This tactic will fill in all possible voids.
- Now we pour out the next portion, and the process is repeated again.
- After the concrete has hardened, the guides must be removed and the resulting space must be repaired with mortar. There is no need to throw away used beacons from the finished screed.
For your concrete floor to be solid and durable, you need to allow it to cure. To do this, you must follow certain rules:
- If the concrete screed was poured in the summer, it must be sprayed with water several times a day for 3 days.
- If the temperature outside the window is very high, then a film is laid on top to retain moisture.
- If work is carried out in winter, the heating should not work in the room.
- The windows should be kept curtained to avoid the heating of the laid mortar by the sun's rays.
- Avoid stressing the floor for 3 weeks.
If you strictly follow these recommendations, you will get a solid and reliable concrete floor.
How to make a concrete floor screed - watch the video:
The procedure for laying a concrete screed is not particularly difficult, but it is important to follow all stages of work, such as preparing the surface of the base, installing beacons, priming, preparing the mortar and laying it. Before starting the installation, it is important to study the device of the concrete screed in order to avoid mistakes that in the future will lead to defects and a short service life of the floor.
