Frequently Asked Questions
Question: "What are the major advantages of Rammed Earthwalls?"
Answer: Earthwalls are a natural material requiring only small amounts of energy and endowing an enviromental responsibility. Earthwalls give a natural appearance and long lasting quality, as well avoiding the "Sick Building Syndrome" (Google it) of commercial building products. Earthwalls have a very good thermal capacity to heat or cool the house by delayed heat transfer e.g. walls cool off overnight and transfer coolness during the summer day. Earthwalls are cheap and very favourable for owner-builders or isolated families, who cannot cost wise easily obtain deliveries of mainstream building material. Unlike concrete, earth walls have a good acoustic resonance.
Question: What does it cost?
Answer: Rammed Earth for owner builders is very low-cost (dare I say "dirt cheap") even if your earth is delivered. The low 5% addition of cement needed is unlikely to blow out the budget, certainly cheaper than delivered brick or cement block. Even with hiring a carpenter to construct your forms, these should easily be attained for a few hundred dollars.
Commercial construction is a different matter with pro-builders labour costs bringing the budget to a par with most other methods of mainstream masonry construction.
Question: "How durable is Rammed Earth?"
Answer: Accelerated erosion tests have been undertaken
by the CSIRO and the Natural Building and Technology Centre. This
involves ramming a test block of your chosen earth, which is exposed to
a high pressure water jet for a set time. Most samples will pass this
test when stabilised with as little as 5% cement.
Potala. Lhasa, Tibet built of Rammed Earth.
Question: "Can you use any soil?"
Answer: No. Topsoil is NOT suitable but most sub-soil/earths are suitable (no organic material).
Clayey earths need the mixing in of sand (vise-versa: sandy earth needs clay) to improve the range of particle sizes which provides for easier mixing and compaction.
Question: "Can on-site earth be used for the walls?"
Answer: Yes. Especially on larger land portions with a greater area of selection. Where only one earth type is available and it is too narrow in composition, additives such as sand, clay and fine gravel can be added.
A basic "drop test" may be used for earth suitability:
Take a hand full of the earth (which should be damp only) compact it by squeezing hand tightly. Then hold out the sample at chest height and drop it on firm ground.
The ideal sample should break up some what but overall stay whole.
If the sample either breaks up totally (too much sand) or stays in one lump (too much clay) it is unsuitable but can be corrected by additions described in the previous question/answer.
Question: "Can white ants be a problem?"
Answer: The CSIRO has published a technical report stating that termites will not burrow in rammed earth walls.
Question: "Does it matter that there is no wall cavity?"
Answer: Rammed earth walls are monolithic and have no cavity. The walls are waterproof due to their clay content and high compaction and repel water in a similar way to the clay lining of a dam. Cavity walls can harbour insects,vermin & rodents whereas this is never a problem with rammed earth walls.
Question: "Why rammed earth walls and not mud brick?"
Answer: Mud bricks require multiple handling to make them and then to lay in place with mortar. Compared to rammed earth walls which are built in situ .
Mud bricks are weaker,not structurally
load bearing & need inbuilt timber or steel columns to support the
brick is much less durable and labour intensive,
Question: "What tools do I need to compact the earth?"
Answer: Commercial builders use an air compressor driven tamper (see "Tech Page" below) which is fast but a considerable outlay to purchase. Also it is very "jumpy" to use and abrasive on light weight forms. Owner builders who have time to build at their own pace would be advised to use a hand held compacter (see "Tech Page below) which is noise and vibration free. Hand ramming-compactor actually gives a much better quality compacted result, this was the method used for centuries (Great Wall China) and our early rammed earth building pioneers, had no high tech tools.
Question: "Can walls be painted?"
Answer: Yes. But rammed walls really only need two coats of clear low cost P.V.A. (Bondcrete) to seal walls. Overall if desired walls can be tiled, rendered, plastered, painted etc. Additionally, lime washes and earth renders can be applied to rammed earth walls.
But all these finishes add a more intensive maintenance program to your home, the precept of rammed earth is to be relatively maintenance free.
If you choose light coloured earth then light reflectivity in the interior will be best.
Quesiton: "How well do rammed earth walls withstand fire?"
Answer: Depending on their thickness, rammed earth walls have an approximate four hour fire rating which is the highest needed in Australian building codes. This is also good news for your insurance premium. Rammed Earth does not burn or emit toxic chemicals as do most other building products.
Outdoor garden wall with
handsplit hardwood shingle cap
(courtesy of Coochie Mudlo Island Mob.)
Roger will be happy to answer further enquiries if you use the Email below!
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