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5 replies
building lightweight concrete blocks under a masonry chimney
Hello!
I am building a summer cottage and currently installing the flooring. I have poured a concrete slab for a masonry stove and chimney, which is about 2 m2 in size and approximately 20 cm high. Since the mason couldn't come for a while, I'm considering using leca blocks or aerated concrete blocks to reach the level of the floor joists, which are about 80 cm above the concrete slab. My questions are as follows:
1. Are there any structural integrity issues with laying these (i.e., leca blocks or aerated concrete) and then building on top of them?
2. Can a supporting beam be drilled and fastened into these materials?
3. Are there any fire/thermal technical issues with the construction?
4. Which is better, leca blocks or aerated concrete?
5. Any other comments?
I am very grateful for the response,
Best regards, ptp
I am building a summer cottage and currently installing the flooring. I have poured a concrete slab for a masonry stove and chimney, which is about 2 m2 in size and approximately 20 cm high. Since the mason couldn't come for a while, I'm considering using leca blocks or aerated concrete blocks to reach the level of the floor joists, which are about 80 cm above the concrete slab. My questions are as follows:
1. Are there any structural integrity issues with laying these (i.e., leca blocks or aerated concrete) and then building on top of them?
2. Can a supporting beam be drilled and fastened into these materials?
3. Are there any fire/thermal technical issues with the construction?
4. Which is better, leca blocks or aerated concrete?
5. Any other comments?
I am very grateful for the response,
Best regards, ptp
1: I did it similarly with lecablock, asked an engineer before and he said it was completely fine strength-wise, I have about 8 meters chimney with four channels wood stove etc.
2: I made a ledge and attached the joists with angle brackets to a horizontal joist (with sill paper underneath) instead, I think it is difficult to attach joist hangers to leca if you intended so.
3: There might be a little thermal bridge when the foundation comes through the floor slab, I put "foam glass" in a layer in the floor slab but I don't think the leca conducts cold that much.
4: Don't know, have only seen lecablock used.
5: Plastered/coated my foundation before we closed the suspended floor.
2: I made a ledge and attached the joists with angle brackets to a horizontal joist (with sill paper underneath) instead, I think it is difficult to attach joist hangers to leca if you intended so.
3: There might be a little thermal bridge when the foundation comes through the floor slab, I put "foam glass" in a layer in the floor slab but I don't think the leca conducts cold that much.
4: Don't know, have only seen lecablock used.
5: Plastered/coated my foundation before we closed the suspended floor.
OK, thanks for your response, this seems promising! I have some follow-up questions related to the previous ones:
2. Yes, the idea was to attach joist hangers to the leca. How did you attach the horizontal beam, did you drill into the leca? Why didn't you use joist hangers on the horizontal beam?
3. What do you mean? What is foam glass?
5. Did you do this also for the part that is under the floor? If so, what is this function?
Best regards ptp
2. Yes, the idea was to attach joist hangers to the leca. How did you attach the horizontal beam, did you drill into the leca? Why didn't you use joist hangers on the horizontal beam?
3. What do you mean? What is foam glass?
5. Did you do this also for the part that is under the floor? If so, what is this function?
Best regards ptp
2: I placed the studs on top of the lying one, like a sill plank, screwed the sill from above with plugs into the leca, but it was mostly to fix it laterally.
3: Foam glass has the same function as cell plastic, got it from my bricklayer who then built the chimney, don't know where he buys it. It is supposed to be a bit more age-resistant than cell plastic, but regular cell plastic probably works too. I placed it in a layer (100mm) in the floor structure to break the thermal bridge from the foundation.
5: Applied slurry to the part under the crawl space mostly because I heard somewhere that you can get ants and other unpleasant things in leca if you don't, it was easily done, just diluted the mortar with more water, but honestly, I don't know if it's necessary.
3: Foam glass has the same function as cell plastic, got it from my bricklayer who then built the chimney, don't know where he buys it. It is supposed to be a bit more age-resistant than cell plastic, but regular cell plastic probably works too. I placed it in a layer (100mm) in the floor structure to break the thermal bridge from the foundation.
5: Applied slurry to the part under the crawl space mostly because I heard somewhere that you can get ants and other unpleasant things in leca if you don't, it was easily done, just diluted the mortar with more water, but honestly, I don't know if it's necessary.
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