I'm planning to build an underground cellar using the random rubble masonry construction method. I've decided on this method to save cost on construction materials, because I have access to a lot of natural stones on my property, and I also have a lot of spare time. The stones are a mix, but mostly granite 10-40 cm / 4-16 inches.
The cellar will be dug into the side of a tall hill with steep slopes. The cavity will be on ground level. The ground is densely packed gravel/silt that is hard to break. If I excavate from above, that would be a lot of material, so instead I plan to dig it out from the side, like a horizontal shaft. The structure will have vertical walls and a circular arched ceiling, to take the load from above. Temporarily supported by wooden beams while I dig and do the masonry.
Please give me some pointers and best practices.
- Strength. What is a suitable wall thickness to make it strong enough to prevent collapse? I'm thinking that I don't need rebar (which is hard together with RRM), because there will be no tension loads. The vertical walls will have almost entirely compression loads. Same for the arched ceiling, the same way an arched bridge works.
- Moisture. What is a suitable type of mortar for strength and to prevent moisture penetration? This is above the water table and in dense ground, but do I still need a liner? Perhaps a French drain (loose gravel around the structure) might be good enough to lead the water away.
- Technique. Either standard stone laying with mortar using a trowel. Or creating wooden forms and stacking stones while pouring concrete.
The cellar will be dug into the side of a tall hill with steep slopes. The cavity will be on ground level. The ground is densely packed gravel/silt that is hard to break. If I excavate from above, that would be a lot of material, so instead I plan to dig it out from the side, like a horizontal shaft. The structure will have vertical walls and a circular arched ceiling, to take the load from above. Temporarily supported by wooden beams while I dig and do the masonry.
Please give me some pointers and best practices.
- Strength. What is a suitable wall thickness to make it strong enough to prevent collapse? I'm thinking that I don't need rebar (which is hard together with RRM), because there will be no tension loads. The vertical walls will have almost entirely compression loads. Same for the arched ceiling, the same way an arched bridge works.
- Moisture. What is a suitable type of mortar for strength and to prevent moisture penetration? This is above the water table and in dense ground, but do I still need a liner? Perhaps a French drain (loose gravel around the structure) might be good enough to lead the water away.
- Technique. Either standard stone laying with mortar using a trowel. Or creating wooden forms and stacking stones while pouring concrete.
