Quite a lot... Concrete contains stones which give it greater wear resistance than self-leveling compound... Also, more kilos of self-leveling compound are needed than kilos of concrete (bags) and self-leveling compound is much more expensive...
How big of a hole are we talking about? A larger hole definitely makes concrete preferable for several reasons as described above. Use concrete first and then putty if you need a finer surface 
Just go for it unless the hole is big enough to park a small car in... but normally for drainage, you fill with leca and pour concrete for the last 7-10 cm or so... But sure, you can add stone to the self-leveling compound, but it will consume a lot of compound... a 25-liter bag doesn't yield many liters... Concrete gives between 10-15 liters... compound around 6-7 liters more or less...Zeb said:
Hello!
We have lots of bags of concrete (fine-grained) left and are thinking of using these to build slopes in the upstairs bathroom instead of buying a lot of expensive self-leveling compound. Does anyone know if this could be detrimental?
Best regards, Lisa
We have lots of bags of concrete (fine-grained) left and are thinking of using these to build slopes in the upstairs bathroom instead of buying a lot of expensive self-leveling compound. Does anyone know if this could be detrimental?
Best regards, Lisa
David:
Keep in mind that you cannot tile/coat, etc., on concrete that is too new. It should ideally dry for 2-3 months. We were advised to use ABS 318 for this very reason, the drying time. The latter only needs about 2 days...
A builder I spoke with, who had quite a bit of experience, had seen bathrooms that after a year had black mold spots in the grout, etc. He claimed this came from all the water in the concrete slab that emerged over time.
Best regards,
PJ
Keep in mind that you cannot tile/coat, etc., on concrete that is too new. It should ideally dry for 2-3 months. We were advised to use ABS 318 for this very reason, the drying time. The latter only needs about 2 days...
A builder I spoke with, who had quite a bit of experience, had seen bathrooms that after a year had black mold spots in the grout, etc. He claimed this came from all the water in the concrete slab that emerged over time.
Best regards,
PJ
Can you shorten that time by turning on the underfloor heating? Beneath the concrete, there's gypsum+chipboard+slatted panel, then there's air about 3 dm (the bathroom is upstairs). Can't the concrete dry out from underneath?
The concrete is at most 2.5 cm thick and will have the opportunity to dry for at least 25 days at room temperature before the waterproofing layer is applied. Do you think that's sufficient? Or should we turn on the underfloor heating? (which requires a bit of work)
Best regards, Lisa
The concrete is at most 2.5 cm thick and will have the opportunity to dry for at least 25 days at room temperature before the waterproofing layer is applied. Do you think that's sufficient? Or should we turn on the underfloor heating? (which requires a bit of work)
Best regards, Lisa
A quick guess, no. Concrete needs some time to cure, and if you remove the water too quickly, it won't cure properly (=cracks, crumbles). The chemical process requires a certain amount of water and time to function.
What do the concrete experts say?
/ama
What do the concrete experts say?
/ama
It is absolutely correct, Ama, then I saw the thickness was 2.5 cm... That is a job for self-leveling compound. For concrete, at least a 5 cm layer is required; otherwise, it is pointless...
Using self-leveling compound is my advice... expensive or not, it's not fun to work with fine concrete when the layer is too thin!!!!
Using self-leveling compound is my advice... expensive or not, it's not fun to work with fine concrete when the layer is too thin!!!!
Ok, I will continue asking... :
What can happen to the concrete if it is too thin? Will it crack? Can it take the waterproofing layer with it when cracking and in the long run cause moisture damage? Or is it just difficult to work with or long drying time that is bad?
Best, Lisa
What can happen to the concrete if it is too thin? Will it crack? Can it take the waterproofing layer with it when cracking and in the long run cause moisture damage? Or is it just difficult to work with or long drying time that is bad?
Best, Lisa
2.5 cm is thin, which makes it a bit difficult to work with... The concrete will "roll" on the surface when you try to level and smooth it with a steel trowel. The risk of drying cracks is probably quite high. Then I think you might get some "creep" on the surface. That is, residual deformations after loading. I mean 2.5 cm is not much, and to avoid cracks in the concrete, you use a reinforcement mesh. That in turn requires about 2-3 cm of cover layer from above and from here, that is about 5 cm. Preferably closer to 10.
The risk of moisture damage is probably the same as with self-leveling compounds really, but as you point out, cracks accelerate the process quite a bit. If I were in your shoes, I would choose a type of fiberglass-reinforced floor compound. It's probably ABS 318 as someone already mentioned. The only thing to think about there is to have the right amount of water and to seal any potential holes in the floor structure. Now we're talking all holes. The compound will find its way into cracks and if it starts to leak, it is anything but fun. You can mix some of the compound to a harder consistency to build a slope if you need one. Otherwise, I think it is 4.5 liters / 25 liter bag normally. And pour, pour, perhaps a notched trowel takes 20 minutes if you mix and pour. A tip is to mix as much as possible directly to minimize joint lines in the compound that occur if it starts to dry on the surface.
The risk of moisture damage is probably the same as with self-leveling compounds really, but as you point out, cracks accelerate the process quite a bit. If I were in your shoes, I would choose a type of fiberglass-reinforced floor compound. It's probably ABS 318 as someone already mentioned. The only thing to think about there is to have the right amount of water and to seal any potential holes in the floor structure. Now we're talking all holes. The compound will find its way into cracks and if it starts to leak, it is anything but fun. You can mix some of the compound to a harder consistency to build a slope if you need one. Otherwise, I think it is 4.5 liters / 25 liter bag normally. And pour, pour, perhaps a notched trowel takes 20 minutes if you mix and pour. A tip is to mix as much as possible directly to minimize joint lines in the compound that occur if it starts to dry on the surface.