Earth Walls

Earth Walls

Rammed Earth Walls

The clamps are suitable for making formwork to build rammed earth walls for DIY or small-scale projects but to stop the forms from flaring out you will need to use thru bolts at about 100mm from the bottom of your forms.

If you are looking for commercial rammed earth formwork try the link below:

Poured Earth Walls

This is just some basic information and is not expert advice and if you search “poured earth” there are some excellent web sites that will give you more detailed information.

Building walls using earth is an art rather than a science. There are so many variables it is impossible to be specific. So do not be afraid to experiment with different mixes and also build some sample walls to get a feel for the mix you are using, then leave your sample out in the elements to see how it weathers.

The type of soil you have available is going to determine the type of mix you are going to use.

Sandy Soils

If you have sandy soil you can use up to 10% cement in your mix (5% is more common) that is one shovel load of cement to 20 shovels of sand. Make the moisture content of the mix about the same consistency as brickies mortar or a cake mix but the dryer the better but the mix still has to wet enough for it to pour. With sandy soil, it is possible to take the formwork off within a few hours or you can slip the forms up to make the next layer of wall. There will be a line between each pour, which can be rubbed off, especially if the wall is still a little wet.

Clay Soils

If you have a soil with a high clay content, up to 70% do not use cement but add straw or something similar to stop the clay from cracking too much. Some people add hydrated lime but again you have to experiment to get your mix right.

How quickly you can take the forms off depends on the weather. On a hot summers day, you can do a pour in the morning and another in the late afternoon. On colder days you have to leave the forms on longer to let the wall dry out, especially with your first pour. If your wall starts to slump (bulges out at the bottom) when you take the forms off the wall than the wall is still too wet and forms have to be left on longer for the clay to dry out. The second layer and subsequent layers dry out more quickly because the moisture is sucked up by the wall that is already built.

When you have built the first layer of the wall, slip the forms up to about 100mm (4”) or more (depending on the weather and the mix) and pour the next layer of the wall, in effect you are making the equivalent of a long mud brick.

The moisture content of your mix for a high clay content wall is the same as a mud brick. Wet enough so it can be rolled into a ball and does not break up if it is dropped on the ground from chest height. Also, high clay content walls shrink a lot, so it is advisable to put some straw in your mix.

Do not use top soil that is, the stuff you grow things in, it has too much organic matter in it so does not bind and will wash away the first time it rains.

The best type of material to use is road base it has about 30% clay content and is used on roads before they tar it and is the material used to make rammed earth walls. If you do not have suitable soil and you are close to a quarry or a supplier than road base can be delivered at very competitive rates per ton.

Poured earth walls are quicker to build than other types of earth wall construction because you only have to handle your wall building material once, from your mixer into your forms and it does not require heavy duty formwork.