The number of requests for info about Rammed Earth was starting to get a bit much so I have compiled a FAQ.

These are some edited emails I have replied to. Note that any answers are my opinion only and the usual crap about getting proper advice applies.

If you have any questions that are not covered here please feel free to contact me                                 Rammed Earth Home Page


Questions in reverse chronological order, change to alphabetical order


Did you tile your bathroom/laundry walls or is rammed earth robust enough to withstand everyday use? Is special sealer required?   top

Nope, we havenít tiled any walls, including wet areas. It hasnít done any damage over 20 years, however we have one of those soap/shaver/shampoo holders hanging from the shower head coming out of a RE wall. Below it is a bit grotty from the soap and stuff that has dripped. If I were doing it again, next time I would tile a susceptible area like that, but given the not perfectly flat nature of RE, not sure how easy it would be.
Where can I hire Rammed Earth formwork?   top
Have a look here riverinarammedearth.com.au/formwork.htm - but please mention to them that you heard about it here.
Can you suggest what to coat our rammed earth house with....the Bee's are eating it. Well maybe not eating it but drilling little holes and breeding in it Thousands of the buggers.   top
Assuming you are in Australia you probably have blue banded bees, a native bee. There's more info here: http://www.zeta.org.au/~anbrc/bluebandedbees.html

We have them tunneling into some earth bricks that fill a gap at the top of a wall but the rammed earth should be too hard for them to burrow in.

I havenít worried about it too much and, perversely, I do enjoy the way they hang on a plant in the evening. HaHaHa.com.au/weblog/index.php?thought=1377

I suppose you could spray them, but they are a relatively harmless critter and they are a native insect that does a good job pollinating plants

Can stormwater downpipes be located within the rammed earth walls without causing cracking? If so, what cover would you recommend?   top

I am not expert but I would say you could do it - with care. We located all electricals within the walls, but that is (obviously) using smaller diameter conduit.

Assuming you are using 100mm downpipes that would leave 100mm covering which (again caveat applies) I would think is more than adequate. The one thing I would do is find the thickest walled pipe I could to avoid any cracking...on the other hand, just thinking about it, maybe something with flexibility would be a better idea so it flexes if put under any pressure.

This is not the best way to do it, but something to consider: We forgot to insert one of the electrical conduits in a vital spot. The solution was to get a circular saw with a masonary wheel, cut a couple of lines and then chip out a channel in the wall. After placing the conduit we bogged it up with wall material. Now, unless I pointed it out you would not even notice where it had been done.

As I said, I think that with care you could do it. Perhaps the best idea would be to make your self a hand rammer and do around the downpipe with that...a little extra work but I love the idea of hiding the pipes and think it would be worth it.

We are doing a monolithic pour and I wondered when you cut doors and windows and how?   top
We did not do a pour, so I can't really help you with doors and windows in that regard. Our construction was section by section, but rammed 600mm (2ft) vertically at a time. When it came to a door or window we simply framed up what we wanted and rammed around it.
If I do a monolthic pour with a 30" footer, do I build the RE wall directly on top of the footer/slab?, and should there be some reinforcement to connect the walls to the slab?   top
We added a row of concrete blocks onto the footer and then backfilled them with concrete, this was to ensure that the earth walls would be above any possible water. A waterproof barrier was placed on top of that.

But there is no reason why you could not place the wall directly on the slab/footings. Again, you would need a moisture barrier to prevent moisture rising up the wall.

As for binding to the slab. I am not sure of the building regs where you are, but in Australia we are required to have the roof tied o the footings via tie-down rods. These are set into the footings, run up therough the walls into the top plate. Everything is then tied down to the top plate to stop the roof blowing away :P

This is probably a good idea :o)
We live in a dry climate (High desert). When preparing the earth/cement mixture for tamping, is water added to the dry mixture to allow the cement to hydrate and provide the strengthening bonding?

If it is, is it better to add it in the mixer to make a very heavy doughy mixture or to tamp the material dry and moisten the material in the form?

Our soil would be very dry and it would seem that some moisture would be needed for the soil to compact and for the cement to bond.

Thanks for your help. Ron
   top
Water is generally added to the mix before it is placed in the formwork. In our case we ised the water into the soil with a bobcat.

I think that if you tried to add the water in the formwork it would be difficult to compact and I doubt it would either compact evenly or completely.
I was thinking of building a RE house. I was wondering what mechanical compactors you used. I was thinking of using a 30cm Vibratory plate compactor, which would fit into formwork I will build myself. - Ross M   top
To be honest, I wonder whenter a flat plate compactor would have enough grunt to pack it properly.

We used (as do most ppl) a backfill tamper. They runn off a compressor and can be thought of as a pogo stick with a trigger. The foot hops up and down compacting the material. The foot is generally around 10cm x 10cm, so has a fairly small surface area compared to a plate and also has a definite thumping action whereas a plate is vibrating.

My suggestion would be to build a small test wall. I would think you would need to put in less material than if using a backfill tamper.
I am looking for rammed dirt that has a mixture of dirt and cement and if fences can be built of this.    top
Yes, you could build fences from Rammed Earth, but with a few provisos:

1) They would need to be built with a mosture barrier beneath them, especially if there is any dampness in the location

2) I would cap them with terracotta tiles so that water is shed off the top - or if not, I would have a fairly steep angle on the top so water drained easily.

3) It would need to be treated with some sort of waterproofing agent e.g. techdry



As you might have figured by the consistent theme, moisture is likely to be your main problem.

Having said that, they would weather beautifully and would last for a very long time even though they were exposed to the elements.

There is a wall at the CSIRO in Sydney that was built about 100 years ago - well, a long time, anyway - and it has no protection. It is showing the signs of age, but it is still remarkably intact and strong.

We are to build a home in Far North Queensland. The home is to have alot of undercover outdoor space. Do you think columns can be constructed using rammed earth?   top
Columns can most certainly be made from RE. If you don't have the proper formwork, it may be hard to make round columns, but square are not a problem.

Depending on what they are supporting will determine what diameter and whether they need an internal support. i.e. We have a single internal column supporting the main beam in the house. To be sure it is strong enough, the RE is surrounding a small steel column...after all, if this column fails, disaster. But if it is only supporting say a roof, pure RE would unlikely be a problem.
How do I fix cracks in a mud brick wall?   top
First question I would ask is "Is it necessary?" Generally I have found that cracks, unless they are letting weather through, add a little character to a building.

If you must fix them, the best way is to make a mud slurry and bog the cracks up. If you have the same mud used to make the bricks it will likely look better, otherwise you may draw attention to the repairs, especially if you get mud all over the place, which, as children know, is one of the principal properties of mud :o)
What is the R rating of rammed earth earth?   top
I know I saw the info around somewhere, but I'll be damned if I can find it.

The only thing I can find, if its any use, is this section from the Bulletin 5 "Earth Wall Construction" by the CSIRO (Commonwealth & Scientific Research Organisation) Division of Building Construction and Engineering.

It says:

3.6.1  Insulation:

The insulation properties of earth-wall are similar to those of concrete or
brickwork.  Actual values are given in the table below.  Good insulation
results from the greater thickness of the wall.

Thickness (mm)
U-value
W/M(squared) (degrees)C
250
2.86
300
2.56
350
2.33
400
2.14
450
1.97

Latest info on R ratings: And it isn't encouraging... The CSIRO has done a study which shows that the insulation properties of Rammed Earth is pretty low.

Is it possible to build retaining walls using rammed earth or will weathering/erosion be too great.   top
I am not an authority on the matter, so whatever I say...

My thoughts are that it would need EXCELLENT drainage behind the wall to keep most of the moisture away. Further, I should imagine that a higher percentage of cement would be advisable and some sort of waterproofing agent be included in the mix.

Have I put you off yet??? :) Just to emphasise, you would have to have a way of excluding moisture from the wall. I have some rammed bricks that have been in the weather for around 3 years...a kind of accidental experiment :)...and I notice that they are much more fragile when damp and they harden up again when dry.
Rammed-Earth seems an interesting method of mass-wall construction. Is it possible or practical to do-it-yourself (with extra hands) or is it only feasible with machinery and a professional crew?   top
Do you mean solo, without machinery? I guess so, since that is how it was done in "the old days". Obviously, with a crew and all the modern whizz-bang machinery it will be SIGNIFICANTLY faster. My suggestion regarding crew is to get one experienced person to act as a foreman under your command.

He can train the rest pretty quickly. Another good idea is to offer a day's free work to someone building somewhere so you can experience what it is like. Doing that was a real eye-opener for me.
Is the cost of construction forms prohibitive for building a single dwelling?   top
Nope, especially if you source the material onsite. Even if you have to truck it in I think it is effective. Our place cost $AUD1000/day for all crew and equipment for 14 working days. House is 17m x 7m with 32m of internal walls and gable ends.
Is it more or less expensive than standard stick built construction?   top
Can't answer for sure. Aesthetically it surely is, but $$$ wise, don't really know.
Has anyone done structural analysis on these structures?..load bearing, etc.   top
I am not sure, but I would imagine so. Check out news:alt.building.earth or news:alt.architecture.alternative someone there will know. However, just looking at it, it would have to have a similar load-bearing strength to concrete. It is thick, hard and solid. I would trust a lot of weight to a 300mm wall.
How do they fare in earthquakes?   top
LOL. Don't know, hope I never find out :-) Richard in Canberra pointed me to this book that apparently has some info on earthquakes, but I haven't read it.
What I'd like to know is where can I get more detailed info on this process? I'm considering this building technique for a house that I want to build   top
I went and gave someone else a day's work to get the feel of it and then used someone with some experience on my crew until I fired him because he was a dipshit. We coped well.
One thing I did notice is that I don't recall the concrete footer that you mention. Is it's purpose to keep the dirt wall from getting soaked?   top
The footers are to general support the load of the house and spread it evenly. They should go down to natural earth so they have a strong foundation that will (hopefully) never move.
Also, you didn't mention whether or not you used a 4-6" concrete cap to support the roof load.   top
No, we didn't use a concrete cap. We attached a piece of timber on top of the walls all the way around and then ran the cyclone bolts through it so it is secure on top of the walls. Everything then attaches to that.
What are cyclone bolts?   top
Might also be called hold-down bolts. Connect the roof to the footings, usually threaded rod (12mm) and effectively create a tie-down from the roof to the ground.
How long did it take to get the rammed earth walls completed? As I recall, it is a rather labor intensive process.   top
Very labour intensive. It took us 14 working days to do (from memory) 300 square face metres. The house is 17m x 7 m with 2 - 4m x 4m rammed rooms inside...
Do you have instructions on how to build the forms for rammed earth walls?   top
Hmm, there's probably a couple of days work writing them up. No, I hired the equipment. My suggestion would be to find someone doing some and go watch closely, even better, get your hands dirty, people are usually grateful for some help.
Can you tell me where to get more information on best compositions of earth mix - have there been tests on this?   top
I gleaned all my info from people like me who had done it before !!

So, what you need is a range of particle sizes from fine (clay) through small sand, coarse sand and then, for aesthetic effect, some shale material. All this combined with about 4% cement compacts into a solid mass. Unfortunately I don't know where my book with all the proportions is, I am going to have to hunt it out, I am getting loads of questions these days.

If I was building again, I would add different materials for interest, maybe different textures in different rooms? Some charcoal, different coloured gravels, bits of interesting rock or wood. I regret not including an old wooden fence post in the wall to use as a coat rack. In those days I was too panicky about what I could and couldn't get away with. In retrospect, it rammed earth is really forgiving.
Can you tell me where to get more information on form design/construction?   top
This is an art/science in itself. It really is too complex to go into here.

My recommendation would be to have a look at some for yourself. No doubt there are many different versions of the same thing and each would have its own dis/advantages. I doubt it would be economical to construct them for yourself for a one-off job. Perhaps there is someone in your area who hires out the gear. That's how we did it.
I am curious: the prefered method seems to call for a maximum depth or wall thickness of 12 inches. Is this fixed, or can any reasonable thickness be used?   top
We used 300mm (12 ") for the main body of the walls. We used 400mm (16") for the gables which are around 4m high. In retrospect the gables are WAY overkill, but it was in the plans so...

I guess it depends on the formwork. I know of people who have made 250mm walls with no problem, the deciding factor is how much weight the walls are going to bear.
Is there anyone commercially manufacturing steel framework for window and door sills?   top
I'm sure there is. If you have the measurements, no doubt it wouldn't be too hard to get an engineer to make them up.
Is it possible to run sleeves (say steel pipe) through the commpacted fill for electrical wiring?   top
Yep. Although we used PVC conduit. I have my environmental reservations about PVC, but it is the easiest, most flexible and reasonably priced method. You just position them as you go. We forgot about one and I cut a chase int he wall with the power saw using a masnary disk. I then used a bolster to chip it out, laid the conduit in place and bogged it up with wall material. Unless I pointed the spot out I doubt you would spot it.
Greetings from the African National Congress. We have read your Netscape article with great interest. The method may be one important answer to our African Housing Problem. At present the South African housing programme is being throttled by high cartel controlled materials and finance costs. Government subsidies cover about a third to a half of materials costs for 56m2 house. We have to bring this down so "own home builders" can build this sized dwelling for about R15,000.00.   top
Whew, this might be a hard one... How many Rand to the Australian $???
We believe we can build cheaply in Africa using on-site sub soil plus sand where necessary, and cement. Plus concrete stone sufficient for footings and floors. Steel door and window frames would have be set as walls are cast. Can this be done?    top
You could do this for sure. However, I think you might find it easier to build the openings and then fit the frames inside, making them on the spot if you can. All mine are out of wood, which is obviously flexible. However, we built around the sizes of doors we already had. SO size was important and it all worked. If your door and window frames happened to be the same width as your walls then it would be very possible and fairly easy, however, I doubt this would be economical compared to having door and window frames of 50 - 100mm.



Mud brick housing is traditional in this country. Construction lacks durability, particularly in heavy rains, flooding or tornado speed winds.

Hmmm, I guess the mud is not compressed which would tend to make it a little more vulnerable to the elements. However, you would have few problems with rammed earth. Unless you waterproofed the exposed areas I would imagine that you would need to stabilise the material with about 4% cement, bitumen or whatever.
What formwork design do you use?   top
The formwork I used was hired, unless you are going to use it many times I don't think it would be worth the effort of building it. Basically it was 17mm formply on steel frames for strength. Each set of forms was 600mm high and they varied in length to allow for wall length variations.

The two sides are held apart by "spacers" essentially pieces of 25mmx25mm hardwood as long as your walls will be thick. The forms are held togoether by "through bolts" pieces of threaded rod that go all the way through both forms and then are tightend up onto the spacers. Spacers holt it apart, through bolts hold forms onto spacers (make sense?). The spacers are removed as you fill the formwork (if you remember :-> ) and the bolts removed when removing the forms. The holes left by the bolts through the walls are simply packed with more of the wall material and compacted with a hammer or something like that. It is invisible.
What method can be used for tying roof to walls?   top
I should imagine that it depends on local building regulations. We had a piece of timber running around the whole toip of the walls, held down by cyclone bolts (see FAQ). The roof was the FIRMLY attached to this piece of timber. In effect, the whole roof joins the wals and the whole thing is tied to the ground.
Is exterior plastering necessary?   top
Definitely not!!! Especially if you want to appreciate the asesthetics of the earth wall. Keep in mind what I said earlier about waterproofing. Verandahs may be a help in keeping the walls dry.

There was a system going around where people rendered the walls with concrete, but why on earth would you want to add such a labout-intensive step that is no needed?
What are your approximate building costs per m2?   top
Hard question. If you mean for the walls only, I can tell you this much:

It took us 14 working days at $AUD1000/day for all the equipment needed and a team of 5 people (including me). We built (from memory) 280 m2 (on the face) of walls. This included hiring a bobcat and compressor and the materials for the walls. The formwork came with the rammers and all the bits and pieces, right down to shovels and wire brushes and cost $AUD200/day.
Can manual labour substitute for mechanical ramming?   top
If you have enough people and they have the strength and committment to the job, but it would be extremely hard work. I know that some of the early settler's houses here in Australia were rammed by hand, but they had little choice. I guess it also depends on the size of the house. If it was a cottage and it was a village effort to build several of them so everyone chipped in, who knows???
What is the depth and breadth of concrete wall footings for 2.4m high wall.   top
Our walls are 300mm thick and the footings were required by our local government authority to be 450mm wide and deep. Many references I have read discuss using rubble footings or natural rock if it exists. I guess it depends on your circumstances. A local engineer should be able to help for sure.
Would rammed earth walls withstand flooding?   top
How deep, how long, how much force? If it is only shallow, you might overcome it by laying a couple of courses of fired bricks to keep the earth walls up a little bit. We have one row (300mm high) of concrete blocks. This also gives you a good start for the formwork instead of trying to get it in the righ position on the footings.

Perhaps if you rendered the lower section with a waterproof material it might work also. If there was just a bit of water hitting it for a few days every once in a while and it wasn't flowing really fast I should imagine you would have few problems, especially if some sort of waterproofing was done.

I have some rammed-earth bricks that have been sitting out in the weather for 3 years and they are still in pretty good condition.
I searched the web for Rammed Earth and came across your page. I have a quick question, can you build two stories w/ rammed earth?   top
Two stories? Yes, in fact there is a building in Germany that was constructed in the 1920's (from memory) that is 5 stories high. The walls are around 750mm thick at the base, getting thinner at each level up.

We have a single story with a loft. i.e. at each end of the house we have rammed gables and then living space in what would normally be the roof cavity. I would srtongly advise against trying to ram gables. It is really hard to get the angle and work y our way to a point. Better would be to build rammed earth to uper floor height and then finish gables with rammed earth bricks, which is how we did the top metre or so.

If you are building a true two-story house, I should imagine rammed earth would be ideal. You would probably need walls around 400mm thick, but an engineer should be able to help you on that.