Hollow brick: Filled vs unfilled

Starting from the following statement from another here

That does not matter. T8 / T9 filled or unfilled always has the same U-value. Only the sound insulation value changes

What should one decide on?
What are the advantages and disadvantages of filled and unfilled?

Thank you.

One disadvantage of hollow bricks is the thin webs. Therefore, they are less compressive and structurally somewhat less load-bearing. It is not uncommon to hear that some bricks are already defective when delivered to the construction site because they are very prone to cracking and partially break when unloading the pallet. The thin webs also make it more difficult to attach large or heavy objects to the wall, e.g., awnings. Cracks in the plaster are also more likely than with filled bricks that have thicker webs. The use of fabric-reinforced plaster can help prevent this, but it negates the cost advantage compared to filled bricks.

Filled bricks naturally also have disadvantages, which vary somewhat depending on the filling (perlite, mineral wool, or the rather rarely found bricks with wood fibers, ...). A commonly mentioned disadvantage is more thermal bridges because gaps are simply filled with mortar or plaster. Joint widths up to 5 mm may be filled with mortar, but in reality, I have also seen wider areas.

From a joint width of 5 mm, the joints must be sealed on both sides of the wall surface with mortar during masonry.

Hi,

Our house was built with T14 bricks; originally, T18 bricks were planned, but they were not available at the time. Even the T14 bricks have the structure and strength of puff pastry, and how I’m supposed to securely mount kitchen cabinets on them later is still unclear to me.

The unfilled T8 bricks are about as delicate as Meissen porcelain and sound like that when tapped. I have serious doubts about whether decent soundproofing can be achieved with them.

Our shell builders also said that in such constructions they spend more time sweeping up curses and shards than actually laying bricks.

And hanging cabinets on such walls is quite complex; you immediately start with chemical anchors etc...

We build with 24 cm T14 bricks and 16 cm ETICS. From today’s perspective, I would definitely consider a wall structure made of 17.5 or 24 cm hollow bricks (which are actually used for interior walls, have high bulk density and a lot of mass, and thus excellent soundproofing) with ETICS. That is how the house we currently live in is built. It probably would have been a good option, but no one really offers that anymore.

Long story short: I would be very critical of a monolithic wall structure with unfilled T8 bricks. I personally consider a simple, as heavy as possible brick with ETICS a better solution. And if you don’t want plastic on the outside of the wall, you can always insulate with stone wool.

Best regards,

Andreas

Hello Andreas,

we have exactly what you consider very critical and not recommendable. Unfilled, monolithic T9 bricks, with thin webs, and we are satisfied.

Our bricklayers were indeed able to work with these without shards, and they are also properly heavy, so that’s not the case. Of course, the webs are very thin, but they don’t just “break easily.”

The kitchen is installed and other cabinets are already attached to the exterior walls. Of course, you need special anchors and should not drill full throttle with a hammer drill on the exterior wall. But I would almost say that’s the case with every modern brick...

During the rough installation of electricity and especially water, you could already notice that the webs break very easily with this brick and the holes/slits become larger than expected if you’re not careful. But you do that once and then you know, afterwards you mortar everything in again anyway.

Best regards

Hi WildThing,

Hello Andreas,

we have exactly what you consider very critical and not recommended. Unfilled, monolithic T9 bricks, with thin webs, and are satisfied.

I'm glad you are satisfied. Do you already live in the house? How is the sound insulation? Honestly, I am a bit worried about our T14 bricks, even though we live in a very quiet residential area.

I would never say that I consider a T9 not recommended. That is beyond my expertise. I only said that personally, based on what I have seen, I view the T9/T8 critically. But that doesn't mean I'm right...

Best regards,

Andreas