Adobe brick making #1: Trial mixes

quite interesting post . are they actual building blocks ?

Thanks MRTRIM.

Yes, these would be actual building blocks. It’s the standard size used around here – just under 12”x12”x6” so that when it is placed on the wall with mud mortar, each brick is as close to exact 12×12x6 as possible. This size makes it easier to estimate the number of bricks and produces a 1ft thick wall.

The mold size takes into account the shrinkage of the bricks when they are dried. This was established by making a test box filled with mud, measured after fully dry. I think we had quite a large shrinkage factor due to the amount of clay in our mix ( I think it might have been around 7%).

You can make larger bricks too, but then it becomes a matter of weight. These already weigh on the order of 20kg (44lbs) apiece. We make 1 1/2 size bricks for the corners, so you can create a locking bond pattern.

so your building something with these blocks ? id like to see a pic of something built with these . what keeps weeds and grass from growing out of them ? id sure hate to have to mow my lawn and my house too ! lol

Hi MRTRIM,

These blocks are only being used for evaluation but these are the very blocks I would use for any building I would do. The beauty of earth blocks is that when your experiments are over, you just bust up the block and put it back where it came from.

No chance of grass growing out of the blocks because there are no seeds in the mix. The binder is straw or woodchips and the blocks are only ready to be made into a structure when they are completely dry. Add sufficient water to a mud brick and it becomes mud again, so the most important aspect of mud brick building is keeping the elements off of the bricks.

In mud brick building, they say “good hat, good boots” is the key ( as it should be for any building method really), so care is taken that there is a good barrier between the foundation and the bricks and that the eaves are sufficient size to keep weather off of the walls ( usually a min of 3ft eaves for a single story building).

The other thing which can be done is to further waterproof walls is applying a lime plaster. This provides a breathable membrane but prevents water penetration. No water = no chance for anything to grow on the walls including algae or moss which is more likely than grass. These are basic principles applicable to any house building.

On the other hand, if your lawn and house were covered in grass, it would be the ultimate in green building :)

I’ll post some pictures of some structures built around here with these kinds of bricks later. You will see that they look like ‘normal’ houses!

Daltxguy, we like to see the building, what are you putting together…

thx guy , im finding this quite interesting . thx for sharing it .

It sounds familiar. My strawbale house is finished (someday) with a layer of cob. Yes Mrtrim it is not easy to run the lawn mower up the outside walls so I make my wife do it. Actually They are pretty weed free.

-- http://woodsongsfurniture.com

ha ha dennis thats why i was concerned about it , im not married ! lol

My wife is getting behind with mowing our house.

Very interesting post.Thanks for sharing it.I too would love to see the progress of this project.
Ha ha good one Dennis and PaBull.

-- Dustygirl Hastings,Ont. Life is too short to sit around doing nothing

Hello Steve! I did not know you were on HR as well. I just stumbled on your adobe posts. Very interesting. How did your second batch of bricks turn out? Have you tried any more? If your adobe bricks don’t work out, you can also look into earthbag construction as an alternative. Using the polypropylene bags to hold the soil means that your filling material does not have to be as strong as the adobe bricks need to be.

Hi Robin,

Ok, well I left the brick for longer than 8 weeks – more like 88 weeks. Those bricks were made when we still living in Christchurch and making the permanent move to Murchison – so the bricks were 250 miles away. Then it was the move and last summer was spent insulating the house for the winter just past.

So the bricks are still there and the tests haven’t been completed. I can say that it looks like adding extra sand has improved the mix. The addition of both woodchips and sand has produced a strong and lighter brick. In the end it’s not a question of if they would work, it’s just a question of getting the right mix.

Earthbag construction has attracted my interest as it is a earth product but I have rejected it as an option for me for 3 reasons: 1. You need a lot of polypro bags, which I don’t favor because I don’t want plastic in my walls or oil based products. 2.Usually earthbag construction uses cement reinforced earth. In my opinion, this takes away the very properties which make earth a good building material – the earth loses its’s ability to absorb and release moisture 3. Our earth building standards in NZ does not cover earthbag construction, meaning that slightly more engineering needs to take place ( earthquakes being the primary concern). With adobe bricks, rebar reinforcement can be built in as you build.

Having said that, I am now favoring roundwood timber framing construction ( timber framing with whole logs) and using adobe brick or earth plaster infill ( ie: as non load bearing walls for interior only walls mainly for radiant heating and as a solar flywheel ). There are many reasons for this but it makes better use of our materials onsite with less processing, and it appeals to my woodworking obsession too.

Thanks for picking up the thread again!

Are there any pictures of your Christchurch?