lava rock as a building material

[gogould]

I was just reading the thread on using cobs. What I do see a lot of on the island is really good lava rock walls. Some of them stunning as art work and craftsmanship. I cannot help but wonder if there would be a way to incorporate them into the concrete structure that uses a post and beam style where the posts and beams are actually reinforced concrete with lots of rebar. The rock could be mortared smooth on the inside and painted with the nice colors.

[Rob Tucker]

Lava can make a nice facade or paving stone. Don't count on it for much else.

[gogould]

It does not appear to have a lot of structural strength, but that is what the concrete and rebar are for. I doubt the termites eat it. Is there recommendations for contractors doing great lava rock walls?

[MarkP]

I have pondered this at great length. What are you hoping to accomplish by using the rock, and I'm not being snide, just practical. Both for practical earthquake protection and to meet code you would need reinforced concrete. In fact, adding rocks would increase the amount of concrete and rebar needed not lessen it so from a pure sustainability standpoint you would lose rather than gain by using rocks. Stone walls don't have this problem, being dry stacked, but that is because the risk of being crushed beneath a 6' garden wall on the property line is so small compared to the risk from a 10' house wall that is also holding up the roof over your head while you sleep.

[Jyoti]

how about cinder (and some lava rocks) being used as a 'cob' material, mixing with cement, and making small, curving cottage walls ?

[gogould]

Hi MarkP the idea is to use the reinforced concrete as plates, sills, structural columns and incorporate reinforced concrete gussets as well. I thought about the possible consequence of the lava rock ending up in a pile of rubble in the house too. It is a tough scenario to get around. I was in the 64 earthquake in Alaska it is hard not to think about that. Not all ideas are good ideas. Still I like the look of the rock and can picture in my mind a dwelling that fits the east side landscape in a really creative and natural looking way.

[gogould]

Hi Jyoti I like the image and think there is a shape and way to reinforce this but end up back at the beginning saying is it worth it. Structural reinforced concrete with cement masonry units with rebar and grouting is really fast and can be used a mortar base that forms curves and so on really nice. I think there would be a way to mix up your mixture for outside curves and so on in a way that would be done at a good speed and provide a first floor outside creativity that would be safe, strong, bugproof, weather resistant, and fun.

[Rob Tucker]

Ah, the old "form versus function" dilemma. If you follow proper engineering techniques you can have both. Concrete is 2,000 year old material and is well understood. The problem lies in asking an insubstantial material to preform in a substantial way. Use the lava or cinder mixes as veneers and you can have both form and function.

That 64 quake was amazing. Best not to forget nature's messages. I remind my clients that ultimately there is nothing made by man that cannot be defeated by nature..... but that doesn't mean we should be stupid.

[gogould]

I like that phrase, "both form and function". That makes the most sense and can produce a safe structure that has some enjoyable features. I get bored with the box thing that we build all the time but there is a good reason for it.