This was a question that came up on one of the social media feeds I get distracted by. “It would make a fine house, be efficient, and long lasting.”
People supporting the idea made comments such as, “Heiau were built of lava rock, and they last hundreds of years.” “Hawaiian walls are made of lava rock, and they last hundreds of years.” “Hawaiians used to build houses out of stone.” “The stone church in Kailua-Kona is still standing and strong.”
Now, I am not going to say, “don’t build with lava.” I actually like the idea, and have seen some very nice lava construction. But I want to point out some things in the earlier comments.
“Heiau were built of lava rock, and they last hundreds of years.” Yes, they were. But the stonework was, and remains solid throughout. They are lava rock platforms on top of which wooden structures were built. The stone portions we look at today are foundations, not the entire heiau. Check out Kamakahonu Heiau and Puʻuhonua o Hōnaunau to see how the structures are used on the foundation.
“Hawaiian walls are made of lava rock, and they last hundreds of years.” True. But, like the heiau, they are solid structures. Some have withstood earthquakes and tsunami, but many have been destroyed. (And like the heiau, many also have been disassembled for use in more modern structures.) In general, heiau and walls require regular maintenance which includes the replacement of rocks that fall off, and “chinking,” a process of surveying the entire face of the structure and using a rock or mallet to tap the rocks back in place and “chink” in small rocks to tighten the structure (the word comes from the sound of the tapping, “chink, chink, chink”).
“The ancient Hawaiians used to build houses out of stone and thatch the roofs.” No, they built stone platforms on top of which they build wooden frame structures and thatched the walls and roofs.
“The stone church in Kailua-Kona is still standing and strong.” It’s also undergoing a $3,000,000+ retrofit. Throughout the islands, there are actually a number of notable buildings made from lava stone and coral lime. Mokuaikaua Church, Huliheʻe Palace, I’ll add more as I think of them. There also are numerous ruins of lava stone buildings from the same era which collapsed over the years due to earthquakes and lack of maintenance.
To build with lava, one needs to remember that not all lava is created equal. Some is quite porous and friable. Think red cinder. Some is extremely dense and strong. Think adz material. There is everything in between. And one rock may comprise a few different expressions, leaving you with strong portions bounded by fault lines which will shatter under stress. So you have to select appropriate lava for construction, or the structure can collapse under its own weight.
Assuming you have an expert in Hawaiian rock construction who knows how to select appropriate material, I see no reason not to use it to build. You will have to send your plans to the county (as with any house construction). There are specific codes for building traditional Hawaiian structures. To use lava rock to build the walls of a home may be possible. I would imagine you will need to hire an architect to draw up the plans and specify rock type, have the rocks approved by an engineer, and then get the county to approve your plans.
Some advantages of rock construction:
- Strong
- Durable
- Stays cool inside
- Stone walls become more beautiful as they age
- If harvested properly, low environmental impact/carbon footprint
- Low maintenance
Some disadvantages of rock construction:
- Very heavy, so construction and foundation costs are high
- Requires much greater expertise (thus cost) than many other types of construction
- Natural stone tends to “de-stick” from mortar as it ages, requiring regular upkeep
- When damaged (earthquakes, impact) it is far more difficult to repair than other types of construction
So, those are just some thoughts about building with lava rock.
Before beginning any construction in Hawaiʻi, you may wish to consider some of the Hawaiian traditions regarding blessings.
This book on building stone walls is not specific to Hawaii, but does have some good practical advice.