FAQ

Answers to frequently asked questions about construction materials

How much adhesive do I need per square meter of tiles?

For standard tiles (up to 60x60 cm) you need about 5 kg of adhesive per m². For large-format tiles (over 60x60 cm) you need 6-7 kg/m² because the adhesive must transfer better.

How do I calculate the number of tiles needed, including an allowance?

We recommend an allowance of 5-15% depending on the complexity of the layout: 5% for simple straight laying, 10% for diagonal, 15% for complex patterns or rooms with many corners.

What is the optimal grout joint width for ceramic tiles?

The standard joint width is 2-3 mm for indoor spaces. For outdoor spaces 5-8 mm is recommended because of thermal expansion. Large-format tiles require a joint of at least 2 mm.

How much grout do I need for my tiles?

The amount of grout depends on tile size and joint width. For 60x60 cm tiles with a 2 mm joint you will need about 0.5 kg/m². Our calculator works out the exact amount automatically.

Can I use the same tiles for the floor and the wall?

Yes, but pay attention to the slip-resistance class. Floor tiles should have an R9-R11 rating for indoor spaces, while wall tiles have no such requirement.

What is the difference between rectified and non-rectified tiles?

Rectified tiles have precisely cut edges at right angles, which allows laying with a minimal joint (1-2 mm). Non-rectified tiles have rounded edges and require a wider joint.

How do I choose the right tile adhesive?

For indoor spaces a standard flexible C2TE adhesive is enough. For outdoor areas, pools or underfloor heating use class S1 or S2. For large-format tiles C2TES1 is mandatory.

How many tiles come in one box?

It depends on size. For 60x60 cm usually 4 pcs (1.44 m²), for 30x30 cm about 11 pcs (1 m²). Check the manufacturer's specifications as they may differ.

Is it necessary to seal the grout?

Yes, especially in damp rooms (bathrooms, kitchens). Sealing protects against moisture and mold and makes cleaning easier. It is applied 24-48 hours after grouting.

How do I prepare the substrate for tiling?

The substrate must be clean, dry, level and load-bearing. Unevenness greater than 3 mm over 2 m must be leveled. Use primer on absorbent substrates and a bonding coat on non-absorbent ones.

What are leveling systems and what are they for?

Leveling systems align tiles while they are being laid. They consist of clips that stay in the floor and wedges that are reused. They ensure a flat surface with no lippage between tiles.

How many leveling clips do I need per square meter?

It depends on tile size: 20-30 cm = 16 pcs/m², 60-80 cm = 4 pcs/m², 100-120 cm = 2.5 pcs/m². Larger tiles need fewer clips.

Can I reuse the leveling clips?

The clips are single-use and stay in the floor. The wedges are reusable and can be used on multiple projects - usually 50-100 times.

Which leveler thickness is best?

The most common are 1.5 mm or 2 mm. For rectified tiles with a minimal joint use 1 mm. For rustic tiles or wider joints use 2-3 mm.

When should I remove the levelers after laying?

Remove the wedges after 24-48 hours, depending on temperature and humidity. The adhesive must be sufficiently dry. Break off the clips with a tap of a rubber mallet parallel to the joint.

Are leveling systems mandatory?

They are not mandatory, but they make it much easier to get a flat surface, especially with large-format tiles. They reduce the need for later grinding and correction.

How do I place the levelers correctly?

Place the clip at the junction of four tiles and push in the wedge until the tiles are flush. Do not press too hard, as you may damage the tiles or the substrate.

Are there different types of leveling systems?

Yes, the most common are the wedge system (economical), the tension system (faster work) and the rotary system (highest precision). Choose according to project size and budget.

Can I use levelers on a wall?

Yes, especially with large-format tiles. Use a faster-setting adhesive and additionally secure the tiles until the adhesive hardens.

How many wedges do I need relative to the clips?

Usually 1 wedge per 3 clips, because wedges are reused. Our calculator works out the optimal ratio automatically.

How much putty do I need per m²?

For standard skim coating you need 1-1.5 kg/m² for one coat. For two coats count on 2-3 kg/m². The amount depends on the condition of the substrate and the desired smoothness.

How much paint do I need per m²?

Average consumption is 0.1-0.15 L/m² per coat. For two coats count on 0.25-0.3 L/m². Consumption can be higher on rough surfaces.

How many coats of paint should I apply?

At least two coats for optimal coverage. When going from a dark to a light color you may need 3-4 coats or the use of a primer.

Do I need to prime before painting?

Yes, priming improves paint adhesion, evens out the absorbency of the substrate and reduces the consumption of the topcoat. It is especially important on new or highly absorbent substrates.

How do I calculate wall area with deductions for windows and doors?

Calculate the total wall area (perimeter × height), then subtract the area of windows and doors. Our calculator does this automatically.

What is the difference between putty for wet and dry rooms?

Putty for wet rooms (bathrooms, kitchens) is waterproof and mold-resistant. For dry rooms standard putty can be used.

How long does putty take to dry?

Depending on layer thickness and conditions: a thin layer 4-6 hours, a thicker layer 12-24 hours. Wait at least 24 hours before sanding.

Do I need to sand between coats of paint?

Usually not necessary for dispersion paints. Light sanding with fine paper (P180-P220) is recommended only if there are drips or impurities.

How do I calculate the ceiling area?

Multiply the length and width of the room. For irregularly shaped rooms, divide into rectangular parts and add up the areas.

What type of paint is best for interior walls?

For living areas, a class 1-2 dispersion paint. For bathrooms and kitchens, a latex or special moisture-resistant paint. For children's rooms, a paint free of harmful emissions.

What is an ETICS system?

ETICS (External Thermal Insulation Composite System) is a thermal insulation system that includes adhesive, insulation material, anchors, reinforcing mesh and finishing render.

How much adhesive do I need to bond polystyrene?

On average 5-6 kg/m² when applied with the ribbon-and-dab method. For full-surface application on flat substrates you need 4-5 kg/m².

How many anchors do I need per m² of facade?

Typically 4-6 pcs/m² for central zones. For edge zones (corners, openings) and windy areas 8-10 pcs/m². Our calculator takes these factors into account.

What polystyrene thickness is optimal?

For energy efficiency, at least 12-15 cm of EPS or 10-12 cm of rock wool is recommended. Check the requirements under the energy efficiency law.

How much reinforcing mesh do I need?

Count 1.1 m² of mesh per m² of facade because of overlap (min. 10 cm). For corners and openings add diagonal strips.

How much finishing render do I need?

It depends on grain size: for 1.5 mm about 2.2 kg/m², for 2 mm about 2.8 kg/m², for 3 mm about 4 kg/m². Actual consumption also depends on the application technique.

Which profiles are needed for a facade?

Base (plinth) profiles for the bottom edge, corner profiles for all edges, window profiles for openings and drip profiles for horizontal joints. Our calculator works out all the profiles you need.

Can I do a facade in winter?

Work at temperatures below +5°C is not recommended. Adhesives and renders need suitable temperatures to dry and set properly.

How long does it take to complete a facade?

For a house with 150 m² of facade allow 2-3 weeks depending on weather conditions. Each layer must dry before the next one is applied.

What is the difference between EPS and rock wool?

EPS is lighter and cheaper, but rock wool is more fire-resistant and has better sound insulation properties. Rock wool is mandatory for high-rise buildings.

How do I choose the facade anchor length?

Anchor length = insulation thickness + at least 40 mm of anchorage into the wall. For 10 cm of polystyrene use anchors of at least 140 mm.

What is the difference between plastic and metal anchors?

Plastic anchors are more economical and prevent thermal bridges. Metal ones have a higher load capacity and are used for heavier cladding materials or poorer substrates.

How do I arrange the anchors on a facade correctly?

Most often a W or T pattern: anchors at the panel corners and one in the middle. Add extra anchors for edge zones. Our calculator shows a visual diagram of the pattern.

Do I need more anchors at the corners of a building?

Yes, edge zones require a higher density - 8-10 pcs/m² instead of the standard 4-6 pcs/m². The edge zone is usually 1-1.5 m from all corners and openings.

Can I fix the anchors through the reinforcing layer?

Yes, this is even recommended because it gives a better bond for the whole system. The anchor is set after applying the reinforcing layer while it is still fresh.

How many anchors come in a pack?

The standard pack is 100 pieces. For larger projects packs of 200 or 500 pieces are also available at a better price.

What are the advantages of anchors with a plastic pin?

They eliminate thermal bridges, do not corrode and are easier to install. The drawback is lower load capacity compared with metal pins.

How far from the panel edge do I place an anchor?

At least 5 cm from the panel edge and at least 10 cm from the edge of the wall or opening. Anchors are placed at the junctions of four panels.

How do I drill the anchor holes correctly?

Use a hammer drill and a bit of the right diameter (usually 8-10 mm). Hole depth = anchor length - insulation thickness.

What should I do if an anchor does not hold well?

Check the load-bearing capacity of the substrate, use a longer anchor or switch to an anchor with a metal pin. For weak substrates there are special injection anchors.

How do I calculate the wall area?

Wall area = width × height. For a room with 4 walls add up all the individual areas. Subtract windows and doors from the total to get the net area.

What is the difference between gross and net area?

Gross area is the total wall area without deductions. Net area is the gross area minus openings (windows, doors). Use the net area when calculating materials.

How do I calculate the surface area of geometric solids?

Our calculator supports 12 shapes: rectangle, cube, cylinder, sphere, cone, prism, pyramid, truncated cone/pyramid, ellipsoid, torus and spherical segment. Each has its own specific formula.

What is the lateral surface area?

The lateral surface area is the area of the sides of a solid only, without the bases. For a cylinder, for example, it is only the curved surface (2πrh), while the total surface area also includes both circles.

How do I calculate the surface area of an ellipsoid?

There is no exact formula for an ellipsoid. Our calculator uses the Knud Thomsen approximation, which gives results with an error of less than 1.061%.

Which unit of measurement is best for entering dimensions?

For construction work meters are most commonly used. For smaller objects, centimeters or millimeters. The calculator automatically converts results into all three units.

How do I calculate the surface area of a torus?

Torus surface area = 4π²Rr, where R is the distance from the center and r is the radius of the cross-section. A torus is a shape like a tire or a doughnut.

What is a spherical segment?

A spherical segment is a part of a sphere cut off by a plane. Segment area = 2πRh, where R is the sphere radius and h is the segment height. It may also include the circular base.

How do I calculate the surface area of a truncated cone?

A truncated cone has two radii (R and r). Lateral area = π(R+r)l, where l is the slant height. The total area also includes both base circles.

Can I save area calculations?

Yes, after calculating you can save the results to history or a project. You can also export a PDF with the calculation details.

How do I calculate the volume of a rectangular box (cuboid)?

Volume of a cuboid = length × width × height (V = a × b × c). For a cube the formula is simpler: V = a³.

What is the difference between a prism and a pyramid?

A prism has two identical bases connected by rectangular sides. A pyramid has one base and side faces that meet at an apex. The volume of a pyramid is 1/3 of the volume of a prism with the same base and height.

How do I calculate the volume of a cylinder?

Volume of a cylinder = π × r² × h, where r is the base radius and h is the height. For example, for a cylinder with a radius of 10 cm and a height of 20 cm: V = 3.14159 × 100 × 20 = 6283.2 cm³.

How do I calculate the volume of a sphere?

Volume of a sphere = (4/3) × π × r³. For example, a sphere with a radius of 10 cm has a volume of approximately 4188.8 cm³.

What is a truncated cone and how do I calculate its volume?

A truncated cone is a cone with its top cut off. Volume = (1/3)πh(R² + Rr + r²), where R and r are the base radii and h is the height.

How do I calculate the volume of an ellipsoid?

Volume of an ellipsoid = (4/3)π × a × b × c, where a, b and c are the semi-axes. If all three are equal, we get a sphere.

What is a torus and how do I calculate its volume?

A torus is a shape like a tire or a doughnut. Volume = 2π²Rr², where R is the distance from the center of the torus to the axis and r is the radius of the tube cross-section.

What is a volume calculator useful for in construction?

It is used to calculate concrete for foundations, tank volumes, the amount of fill material needed, capacities of cisterns and pools, and excavation volumes.

How do I calculate the volume of an irregular shape?

Divide the irregular shape into simpler shapes (rectangles, cylinders, cones) and add up their volumes. Our calculator lets you add multiple shapes.

Can I convert the results into liters?

Yes, 1 dm³ = 1 liter. Divide a result in cm³ by 1000 to get liters, or multiply m³ by 1000 to get liters.

What is self-leveling compound and what is it used for?

Self-leveling compound is a self-leveling mass used to level floors before laying the final covering (tiles, laminate, parquet). It is used to correct unevenness of up to 10 mm.

How much self-leveling compound is needed per square meter?

Consumption depends on layer thickness. The standard is 1.7 kg/m² for each millimeter of thickness. For a 5 mm layer you need about 8.5 kg/m².

What are the minimum and maximum thickness of self-leveling compound?

The minimum thickness is usually 2-3 mm, and the maximum is 10 mm in one layer. For larger unevenness it must be applied in several layers.

Is a primer needed before self-leveling compound?

Yes, applying a primer is recommended to improve adhesion and prevent the substrate from absorbing water from the compound too quickly.

How quickly does self-leveling compound dry?

Walking is possible after 3-4 hours, but you should wait 24-48 hours before laying the covering, depending on layer thickness and room humidity.

How many blocks are needed for masonry?

The number of blocks depends on the dimensions of the block and the wall. Our calculator automatically calculates the required number of blocks, including joints and a reserve for cutting.

What is the difference between mortar, thin-bed adhesive and PUR foam?

Mortar is used for standard brick and concrete blocks (10 mm joint). Thin-bed adhesive is for aerated concrete (2-3 mm joint). PUR foam is the fastest method for aerated concrete.

How much mortar is needed for masonry?

Mortar consumption depends on block size and joint width. For standard brick with a 10 mm joint, count about 25-30 kg/m² of wall.

What is aerated concrete (AAC/Ytong)?

Aerated concrete is a lightweight building material with good thermal properties. It is laid with thin-bed adhesive or PUR foam. It is lighter than standard brick.

How do I calculate the area of openings for windows and doors?

In the calculator you can add openings by entering the width and height of each opening. The opening area is automatically deducted from the total wall area.

Can I save my own block dimensions?

Yes, signed-in users can save custom block templates with their own dimensions and select compatible laying methods.

How much concrete do I need for a slab?

Concrete volume = length × width × thickness. For a 5×4 m slab 15 cm thick you need 3 m³ of concrete. We recommend a 5-10% reserve.

What is the difference between hand-mixed and ready-mixed concrete?

Ready-mixed concrete from a batching plant is more consistent and more economical for larger quantities. Hand mixing is more practical for smaller projects up to 1-2 m³.

How much aggregate do I need for hand-mixing concrete?

For 1 m³ of M25 concrete you need about 350 kg of cement, 1800 kg of aggregate (sand + gravel) and about 175 liters of water. Our calculator computes the exact quantities.

What is a concrete class (e.g. C25/30)?

The concrete class indicates compressive strength in N/mm². C25/30 means a characteristic strength of 25 N/mm² on a cylinder and 30 N/mm² on a cube after 28 days.

Can I pour concrete in low temperatures?

Pouring concrete below +5°C is not recommended without special measures (heating, admixtures). At lower temperatures concrete sets more slowly and may freeze.

How do I calculate the amount of reinforcement for a slab?

Slab reinforcement depends on span and load. A Q335 or Q503 mesh is typically used (Ø8 or Ø10 bars at 15-20 cm spacing in both directions).

What is a stirrup and what is it for?

A stirrup is reinforcement that wraps around the longitudinal bars in beams and columns. It carries shear forces and prevents buckling of the longitudinal reinforcement.

What is the minimum distance of reinforcement from the concrete edge?

The concrete cover is at least 2.5-5 cm depending on exposure conditions. For foundations in soil, 5-7 cm is recommended.

How do I calculate the weight of a rebar?

Rebar weight: Ø8=0.395 kg/m, Ø10=0.617 kg/m, Ø12=0.888 kg/m, Ø14=1.208 kg/m, Ø16=1.578 kg/m. Our calculator automatically computes the total weight.

What is the difference between reinforcement mesh and individual bars?

Meshes (Q-meshes) are faster to install and more economical for slabs. Individual bars are used for beams, columns and more complex structures.

How do I determine the required insulation thickness?

Thickness depends on the target U-value and the wall material. For a passive house the target is U=0.1-0.15 W/m²K, which requires 20-30 cm of insulation depending on the type.

What is the U-value?

The U-value (thermal transmittance) shows how much heat passes through 1 m² of wall. A lower U-value means better insulation. The unit is W/m²K.

What is the difference between EPS and graphite EPS?

Graphite EPS has better thermal conductivity (λ=0.031-0.033 W/mK) than regular EPS (λ=0.035-0.040 W/mK), so a smaller thickness is needed for the same effect.

When should I use rock wool instead of EPS?

Rock wool is mandatory for taller buildings (fire safety), is better for sound insulation and is vapor-permeable. EPS is lighter and cheaper for standard applications.

How much can I save with insulation?

Savings depend on the initial condition and insulation thickness. On average, a 40-60% reduction in heating costs is expected. Our calculator estimates annual savings.

How do I calculate stair dimensions?

Blondel's formula: 2h + b = 63 cm (±3 cm), where h is the riser height (16-18 cm) and b is the tread depth (28-32 cm). Our calculator automatically checks ergonomics.

How many risers do I need for a floor height?

Number of risers = total height / height of one riser. For a standard floor height of 280 cm and a riser of 17.5 cm you need 16 risers.

What are winder steps?

Winder steps are used in L- or U-shaped stairs instead of a landing. They allow a change of direction in a smaller space, but are less comfortable.

What is the optimal stair slope?

The optimal slope is 30-38°. Steeper stairs (>42°) are uncomfortable and dangerous, while gentler ones (<25°) require a lot of space and are impractical.

How do I calculate a spiral staircase?

For a spiral staircase, enter the total height, diameter and rotation angle (360° = full circle). Tread depth is measured on the walking line (2/3 of the radius from the center).