Masonry block

What is a masonry block, and how does it differ from a brick?

A masonry block, in Slovak a tvárnica, is a large-format wall unit that is noticeably bigger than a brick. A wall built from blocks goes up in fewer units and fewer joints, so the work is faster, but each unit is heavier and usually needs two hands or a hoist. A brick is small enough to be laid one-handed. The word covers several materials, and the material decides the wall's weight, its thermal behaviour, its sound insulation and how it has to be detailed.

Slovak practice keeps the two words apart. Tehla is the small unit, most often seen as facing brick on a facade. Tvárnica is the larger unit used for the structural and infill walls behind the facade. This article is the umbrella: it explains the families that sit under the word, and each family has its own page linked below.

Which families of masonry block are used in Slovak residential construction?

Seven families cover most of what is sold and built. The table compares their material, how the unit is laid, and what the wall needs for insulation.

Family	Material and character	How it is laid	What the wall needs
Ceramic block	Fired hollow clay, with a structural or a thermal grade	Ground units in a thin bed of mortar, or in a full mortar bed in renovation	A thermal grade can make a single-leaf wall with no added insulation. A structural grade normally needs an external insulation system.
Thermal ceramic block	Fired clay with the cavities filled with mineral wool or perlite	Thin bed or mortar foam, with careful workmanship	Built to stand alone as a single layer, so the wall often needs no separate insulation system.
Aerated concrete	Autoclaved, porous and light	Thin-bed adhesive, fast and precise	Good thermal performance on its own, but it needs a plaster system and careful moisture control.
Lightweight (expanded-clay) concrete block	Concrete made with lightweight aggregate	Ordinary mortar, similar to a dense block	Insulates better than ordinary concrete, and is often used for infill and partitions, with insulation added on external walls.
Ordinary concrete block	Dense concrete, heavy and cheap to make	Full mortar bed	Needs insulation on an external wall, and waterproofing where it meets the ground.
Shuttering block (ICF)	Hollow foam blocks filled with concrete, which stay in place	Stacked dry and interlocked, then reinforced and poured	Insulation is built in, because the foam stays in the wall as permanent formwork.
Sand-lime block	Lime and sand, autoclaved, dense and heavy	Mortar, or thin bed for products made for it	Low insulation value on its own, so external walls need added insulation. Good mass for sound.

How are masonry blocks laid, and what does the method change?

The laying method follows from how accurately the unit is made. A ground block with machined bed faces can be laid in a thin layer of mortar, which keeps the joint thin and the wall true. A block with rough faces needs a full mortar bed, which is heavier, slower and produces a thicker joint. Ordinary mortar conducts heat better than the block around it, so a thin joint also helps the thermal performance.

Whatever the family, units are laid in a bond pattern so that the joints do not line up vertically. Reinforced concrete ring beams are placed at the floor levels and at the top of the wall, and lintels sit over openings. These elements are where the wall is most often weak or the most heat escapes, so they should be designed with the block and not added afterwards.

• Thin-bed laying suits ground ceramic blocks and aerated concrete, and gives the most accurate wall.
• Full mortar bed suits rough-faced concrete and some older products, and is slower.
• Dry interlocking suits shuttering blocks, which are then reinforced and filled with concrete.

Which masonry block suits which wall?

The wall's role decides the family more than any single property does. A load-bearing external wall needs strength and thermal control together, while a partition needs only to be light and to stand on its own. The table lists the four roles most often asked about in residential design.

Wall role	Suitable families	Why
External load-bearing wall	Ceramic (thermal or structural), aerated concrete, shuttering block, or dense block with insulation	The wall carries loads and must control heat, so the insulation strategy matters as much as the unit.
Internal partition or infill	Lightweight concrete, aerated concrete, or light ceramic	Lower weight, easier to cut and fix to, and suitable where the wall is not carrying the floor above.
Basement or ground-contact wall	Dense concrete block with waterproofing, generally avoiding porous units	Ground contact and water pressure need a dense, durable material with a waterproofing system.
Acoustic party wall between dwellings	Dense sand-lime, ordinary concrete or ceramic, ideally as separated leaves	Mass helps to block airborne sound, and a separated double leaf usually performs better than one solid leaf.

For a basement, the tanking and drainage detail matters more than the unit. For a party wall, the specification should come from the acoustic design rather than from the family name.

How is a masonry block different from a ceramic block?

A ceramic block is one family inside the umbrella term, so the question is one of scope. Masonry block describes the size and role of the unit, while ceramic block describes the material. A designer who asks for masonry blocks has not yet chosen a material, and a designer who asks for ceramic blocks has already excluded aerated concrete, concrete and sand-lime. In practice the two words are often used loosely, which is why a specification should name the family and the grade, not just the word tvárnica.

Do masonry blocks need insulation?

Not all of them. Thermal grades of ceramic blocks and aerated concrete can build an external wall with good performance on their own, while dense concrete and sand-lime units conduct heat much more readily and need insulation added. The insulation strategy changes the moisture balance, the junctions and the detailing at lintels and ring beams, so it cannot be treated as a later detail. Where the design targets a very low heat loss, the thermal bridges at joints and openings usually decide the result as much as the unit does.

What do clients most often get wrong about masonry blocks?

The most common mistake is to treat the block as the whole wall. Mortar, plaster, insulation and junctions together set the real performance. The second is to assume that heavier means better insulated. Weight adds mass, which helps with sound and with stable indoor temperature, but it does not add thermal resistance. A third is to put a porous block where it will be wet, such as in a basement or against the ground, and then discover the problem after the plaster has failed.

• Choosing the cheapest unit without pricing insulation, labour and plaster together.
• Assuming a product name tells you the thermal performance of the finished wall.
• Ignoring the joints, reveals and ring beams, where most of the heat escapes.