I have a newer house in "white light concrete" with 100 mm polystyrene + plaster as the facade. Now I am going to build an extension with cinder block walls. I want to connect a cinder block wall perpendicularly out from my plastered facade. The cinder block wall will be plastered externally with the same plaster as the existing wall. I have cast a slab on the ground for the extension.
To ensure the wall, which will be three meters high, is sturdy, I plan to drill in rebar through the plaster & polystyrene into the light concrete every third course.
How should I proceed where the cinder block wall meets the plaster?
- Cut a 250 mm wide groove and remove the plaster & polystyrene so that the end of the cinder block meets the light concrete? (Difficult and hard to make it look good? Should I glue the cinder block to the light concrete in that case?)
- Let the cinder block end with a thin gap against the plaster and apply an elastic joint in between. (Simple)
- Apply mortar to the short side of the cinder block and let the cinder block adhere to the plaster? (also simple, but what happens if the cast slab settles? Then the plaster might bulge...).
How would a professional solve this?
To ensure the wall, which will be three meters high, is sturdy, I plan to drill in rebar through the plaster & polystyrene into the light concrete every third course.
How should I proceed where the cinder block wall meets the plaster?
- Cut a 250 mm wide groove and remove the plaster & polystyrene so that the end of the cinder block meets the light concrete? (Difficult and hard to make it look good? Should I glue the cinder block to the light concrete in that case?)
- Let the cinder block end with a thin gap against the plaster and apply an elastic joint in between. (Simple)
- Apply mortar to the short side of the cinder block and let the cinder block adhere to the plaster? (also simple, but what happens if the cast slab settles? Then the plaster might bulge...).
How would a professional solve this?
A little depends on the size of the extension and the ground conditions. The main principle is that the extension is isolated from the existing structure using a movement joint. The extension should have a foundation that prevents it from moving differently than the existing building. In this case, you should be able to remove the plaster from the old house so that the leca wall is directly against the styrofoam and then place a soft joint between the old and new plaster. It's probably not super easy to make it look good.
Buggarn, sketching something similar. Aerated concrete in the existing building and aerated concrete or leca AND wood in the extension. Wood wall closest to the existing wall and leca for the rest. It will be about 50/50.
How did you decide to build with leca and not aerated concrete? Interested in your thought process.
How did you handle the new "slab on grade"? Did you attach the new one with iron to the existing slab? Or are you letting it "move freely"? I've seen indications that it might be good to let it move freely due to settling. I suppose we're talking from a few millimeters to maybe even an inch? But it surely depends on whether you live on rocky ground (like me) or if you live on 50 meters of loose sand or the like. I assume it depends.
Here's my thinking. Since aerated concrete is good at absorbing water, I would like the two buildings to be separated. This makes it difficult/impossible for moisture to migrate from one building to the other. This is because of construction defects or a water leak (in some way).
My problem now is that I can't quite wrap my head around how to solve the junction between the new wooden wall and the existing wall (stucco + aerated concrete). Since I am building with wood right there, I think I want as little (none!) contact surface between the existing wall and the new wall's studs. I imagine a substantial soft joint by means of some type of spray insulation or other unpleasant and environmentally harmful material. It's possible to use steel studs, but I don't know if one _can_ use these in exterior walls for structural reasons.
How did you decide to build with leca and not aerated concrete? Interested in your thought process.
How did you handle the new "slab on grade"? Did you attach the new one with iron to the existing slab? Or are you letting it "move freely"? I've seen indications that it might be good to let it move freely due to settling. I suppose we're talking from a few millimeters to maybe even an inch? But it surely depends on whether you live on rocky ground (like me) or if you live on 50 meters of loose sand or the like. I assume it depends.
Here's my thinking. Since aerated concrete is good at absorbing water, I would like the two buildings to be separated. This makes it difficult/impossible for moisture to migrate from one building to the other. This is because of construction defects or a water leak (in some way).
My problem now is that I can't quite wrap my head around how to solve the junction between the new wooden wall and the existing wall (stucco + aerated concrete). Since I am building with wood right there, I think I want as little (none!) contact surface between the existing wall and the new wall's studs. I imagine a substantial soft joint by means of some type of spray insulation or other unpleasant and environmentally harmful material. It's possible to use steel studs, but I don't know if one _can_ use these in exterior walls for structural reasons.
The slab on grade is completely independent from the house's slab. I placed asphalt paper between the new and existing slab. The slab was poured last fall, and I hope it has settled over the winter. The reason I'm building with LECA is partly because I have leftover lecablocks from another project. Additionally, I can plaster it with the same plaster as the house. Between the new LECA wall and the existing plaster wall, as you suggest, there will be some type of insulation, foam sealant, or similar. When I build the LECA wall, I plan to insert reinforcement every third course. I considered letting this go through the insulation to the aerated concrete in the existing wall. That is, drilling holes through the plaster, insulation, and about 10 cm into the aerated concrete. The purpose is to brace the LECA wall, but I'm not sure it's a good idea. If the slab starts to move, the reinforcement will break against the plaster? It's probably better to let the extension be completely separate. In my extension, one wall will be made of LECA, the other two are sliding sections, so the stability of the building must come from the LECA wall, two glulam columns, the roof, and possibly attachment to the existing building. A few weeks ago, we measured 35 meters per second in the gusts here. That makes you a bit thoughtful.
I'm just a happy amateur. But, if you have a building that weighs a number of thousand kg and the ground settles and you have reinforcement that "pulls" on the existing wall, you might not need to be a rocket scientist to understand that there might be cracks because it will sit like a rock in the existing wall.
My wall will be fixed to the existing wall using larger size aerated concrete screws. Any settling will likely pull the screws out of the wall but probably won't cause any damage other than things being really well anchored. Maybe you could work with chemical anchors, but I don't think it will be necessary. Maybe. But oh well. Early days.
I will have sliding sections and fixed sections larger size like you, but it will be in the part where the wall is built in wood. So the fastenings will be done in wooden studs.
Yes. It's windy. Yes. It will be reinforced according to all the proper standards. Often when I read, it says that "you can" reinforce. As if the products are prepared for this but they seem to leave the decision to the executor. Likely because in some cases it is completely unnecessary. But, as a happy amateur, one has a poor grasp.
How did you solve the slab and existing drainage? Did you leave it or? The slabs end up at different depths.
My wall will be fixed to the existing wall using larger size aerated concrete screws. Any settling will likely pull the screws out of the wall but probably won't cause any damage other than things being really well anchored. Maybe you could work with chemical anchors, but I don't think it will be necessary. Maybe. But oh well. Early days.
I will have sliding sections and fixed sections larger size like you, but it will be in the part where the wall is built in wood. So the fastenings will be done in wooden studs.
Yes. It's windy. Yes. It will be reinforced according to all the proper standards. Often when I read, it says that "you can" reinforce. As if the products are prepared for this but they seem to leave the decision to the executor. Likely because in some cases it is completely unnecessary. But, as a happy amateur, one has a poor grasp.
How did you solve the slab and existing drainage? Did you leave it or? The slabs end up at different depths.
The solution with reinforcement into the existing wall would consist of a total of 8 pieces of 10 mm reinforcing bars, which I plan to secure with chemical anchors. I thought of making the holes in the plaster larger, maybe 14 mm. This should allow for movement and prevent any stress fractures. However, I am not going with this solution as I do not want to make so many holes in the plaster.
When I was building, we prepared some "hard surfaces" for potential awning attachments. These are areas where the insulation was replaced with lightweight concrete. We sawed 10 cm thick slabs of lightweight concrete and glued them to the load-bearing lightweight concrete wall. These surfaces were then plastered together with the rest of the wall. You can hear from the sound where these surfaces are when you tap. Here, I plan to attach the roof structure with long thick threaded rods and chemical anchors, but only so that horizontal forces can be absorbed. I make the holes in the beam oval and use large mounting washers. I don't tighten it hard but lock the nut with a locknut.
Your solution with lightweight concrete screws will surely work. Just remember that you have a layer of plaster and then insulation. If you load the surface by having too small a contact area/tightening the screws too hard, you might risk damaging the plaster.
I haven’t done anything about the existing drainage. I poured the slab right over the pipe. If problems arise there, it is likely that I'm already buried significantly deeper than the drainage...
The new slab lies on a bed of crushed stone on a slope. No other drainage. Rainwater from the roof is directed to a soakaway.
Good luck with your construction.
When I was building, we prepared some "hard surfaces" for potential awning attachments. These are areas where the insulation was replaced with lightweight concrete. We sawed 10 cm thick slabs of lightweight concrete and glued them to the load-bearing lightweight concrete wall. These surfaces were then plastered together with the rest of the wall. You can hear from the sound where these surfaces are when you tap. Here, I plan to attach the roof structure with long thick threaded rods and chemical anchors, but only so that horizontal forces can be absorbed. I make the holes in the beam oval and use large mounting washers. I don't tighten it hard but lock the nut with a locknut.
Your solution with lightweight concrete screws will surely work. Just remember that you have a layer of plaster and then insulation. If you load the surface by having too small a contact area/tightening the screws too hard, you might risk damaging the plaster.
I haven’t done anything about the existing drainage. I poured the slab right over the pipe. If problems arise there, it is likely that I'm already buried significantly deeper than the drainage...
The new slab lies on a bed of crushed stone on a slope. No other drainage. Rainwater from the roof is directed to a soakaway.
Good luck with your construction.