ᐅ Lightweight expanded clay aggregate (LECA): Advantages and Disadvantages, Thickness, Suppliers

11ant schrieb:

I would also have no concerns about using pumice or expanded clay (for all walls, exterior, interior, and even the party wall), but for aerated clay blocks I would choose sand-lime brick for the party wall.

What exactly is the difference between expanded clay and pumice?

We are building with pumice from Meurin. The blocks are filled with perlite inside, similar to Poroton.

Mar_Mar schrieb:

Nope, each one individually 😉 The neighbors have already signed with Schwabenhaus, and their build will probably be shorter than ours. We are in regular contact and also cooperate with each other. What should be considered, or on which points do we or the construction companies need to coordinate?

It’s generally good that neither of you are building a basement. That already eliminates the biggest risk. Personally, I would still recommend using the same supplier. And if you don’t want to do much work yourselves, the price for a prefab house is about the same as for a solid / conventional build. Do you have a complete breakdown of the costs for the conventional build? It is just as expensive as a prefab house. So, if that’s too expensive for you, I would strongly advise calculating all construction costs including additional expenses, in order to adjust either the budget or your expectations.

danielohondo schrieb:

What exactly is the difference between expanded clay and pumice?

Oh dear, you’ve really caught me there. How do I explain this to my child... or put it simply for someone who is neither a geologist nor a chemist, but a technical salesman and a decades-long experienced generalist — clear and understandable, but not wrong? Well, I’ll try my best and hope I don’t embarrass myself too much:

So, initially there were two basic ideas that led to three products.

On one hand, there was a desire for a building material as strong as concrete but without its poor thermal insulation. So, a concrete mix was taken, but without the gravel-like aggregate, and a technique was invented that is somewhat comparable to a yeast dough with a sort of “pyrotechnic” leavening agent. This yeast-dough-like concrete was called aerated concrete and got its brand name (which, like “Tempo” for paper tissues or “Tesa” for adhesive tape, is commonly used as a generic term) from the first letter of the town Yxhult. That covers “aerated concrete.”

The second basic idea was simply “what to do with this useless stuff and how to turn it into money.” The Laacher See volcano – about eleven thousand years ago, long before stone houses were built – erupted like an overactive popcorn machine, showering volcanic rock fragments over the “Neuwied Basin.” The farmers had huge amounts of it under their fields, and the birds didn’t eat it. But when mixed with concrete, it could be used to build sturdy, fireproof field barns. When builders talk about “pumice,” they mean this pumice concrete block or “lightweight concrete block.” Note that strictly speaking, “lightweight aggregate block” is a somewhat different product, often made with industrial rather than volcanic slag.

In a similar area not far from Koblenz, in the Westerwald region, there’s the pottery-making district, also blessed with soil that can be troublesome or useful depending on how you use it; the treasure here is called “clay.” “Kannenbäcker” means “potters.” Again, “expanded clay” is a shortened term used when referring to a building material. It is a similar type of concrete block, but here a lightweight concrete block is made from a porous aggregate created by bonding expanded clay. A “porous structure” is – don’t forget this preliminary note! – a loose arrangement of “macromolecules.”

The essential difference between pumice and expanded clay could be – as simply explained as possible with the preliminary note in mind – that in both cases the industrial stone products are a type of cement-based block. The “popcorn” pumice formed in a volcano at very high temperatures long ago but is now combined in a cold manufacturing process; whereas with expanded clay, clay pellets (produced industrially now, not volcanic from long ago) are heated in a firing process, causing them to expand. These pellets resemble the smaller granules found in hydroponic sack substrates (but naturally are concrete gray due to other ingredients).

All three products result in stable “artificial stones” with structurally high strength and decent thermal insulation values. Although “pumice” and “expanded clay” have different “origins,” they effectively share very close properties, whereas “Ytong” (careful, brand name!) is clearly a different category that even laypersons can easily distinguish with the naked eye, having much lower density and being friendly for DIYers because it can be cut with a wood saw.

So, dear readers, before you start dreaming nonsense from this: your explaining uncle is no natural scientist, and these explanations are inevitably imperfect attempts meant to be understandable even to East Frisian blondes – in the Bible, they’d be called “parables” ;-)

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Nida35a schrieb:

Another statement from our general contractor was that he has never seen mold in a lightweight expanded clay aggregate house, whether with or without a mechanical ventilation system. We can confirm this for our two houses (without mechanical ventilation).

This is also a topic that still needs to be clarified. We "actually" do not want a ventilation system, which, for example, Lec***** would not install at all. We currently have passive window frame ventilation and find it terrible (it whistles, is dirty, and drafty). But I think in the long run, it still makes sense to have ventilation. At least preparations can be made.

Sunshine387 schrieb:

It's generally good that you both have definitely decided against building a basement. That already eliminates the biggest risk. Personally, I would recommend using the same supplier. And if you don’t want to do much of the work yourselves, the price for a prefabricated house is just as high as for a solid-built house. Do you have a complete breakdown of the costs for the solid house? It’s just as expensive as a prefab. So if that’s too expensive for you, I would strongly suggest calculating the total construction costs including all additional expenses to either adjust the budget or your requirements.

As I wrote in my initial post, prefab houses are not an option for us. We have thought it through thoroughly and will definitely go with solid construction. Whether it’s a prefabricated solid house or built brick by brick still needs to be decided, but it will not be timber frame. We are also currently in a thread about the building material lightweight expanded clay aggregate, not about the advantages of prefab houses. And just because my neighbors went ahead and already signed does not mean we will follow suit. If you reverse the question, one could also ask why they did not consult us. But that’s not the point and everyone is free to do as they please. No one said it’s too expensive for us. We know our costs and options very well.

Can anyone share some insights on the disadvantages of prefabricated clay aggregate (expanded clay) building components? Looking at the data, it seems worth considering a 42cm (16.5 inches) thick wall if building monolithically.

Another general question: All solid masonry house providers using traditional brick or block construction require installing mechanical ventilation (as mandated), but Lech*** with expanded clay does not, even though it is just as airtight. Why is that? Aren’t the same regulations applicable to all?