Rammed earth walls: natural and sustainable living

 

‘Rammed earth’ is a technique for constructing foundations, floors and walls from natural raw materials such as earth, chalk, lime or gravel. With the lowest enviromental impact of all building techniques currently used in the commercial construction industry, rammed earth is receiving growing attention and becoming more and more popular with architects, builders and clients alike. In this short post, we tell you a little more about the technique.

Rammed earth walls RISE Design Studio architect west london

Mixing it up

Rammed earth walls are made by ‘ramming’ a mixture of materials into place between flat, temporary panels called ‘formwork’. The panels are normally made of wood or plywood and they are clamped around the earth to make sure it doesn’t bulge when compressed. The materials rammed into the formwork generally include gravel, sand, silt and a small amount of clay.  An additive like lime, cement of asphalt is often added to make it extra strong.

The mixture is compressed inside the formwork by a mechanical ram and compacted to approximately 50% of its original height. The compression takes place in stages, usually in depths of 10cm to 25cm, and this is repeated until the top of the formwork is reached. This is the part of the process that results in the beautiful layers sometimes seen in rammed earth walls.

After the wall has been completed, the formwork is removed and a surface texture can be applied, e.g. by wire brushing or carving. The wall is normally too hard to work on after about one hour. As the walls dry and harden (ideally in warm weather), the compression strength of the rammed earth increases to a maximum of 4.3MPa (620 psi). This is less than concrete but sufficiently strong for domestic buildings.

Environmentally-friendly

Cured rammed earth has a high thermal mass. This means that it absorbs heat during the day and releases it at night, which reduces heating and cooling costs. Environmental impacts are also kept low if the amount of processing of rammed earth materials is kept to a minimum (i.e. artificial additives) and material is sourced locally where possible. Most of the energy used in the construction of rammed earth is in quarrying the raw material and transporting it to the site.

Healthy home

The composition of rammed earth allows it to absorb and release humidity from the inside of a building. This improves air quality, particularly for people who suffer from asthma. Rammed earth is also inorganic, which means that it won’t decay and does not support the growth of mould.

Back to our roots

More than 30% of the world’s population uses earth as a building material, hence this technique is not new. Properly constructed rammed earth can also last for thousands of years, demonstrated by the many ancient structures built using this technique which are still standing around the world.

It has received growing attention in recent years as the construction industry and its customers have a growing sense of the need for environmentally friendly and sustainable building practices. Not only does the technique offer opportunities for carbon-neutral building projects, the technique can be employed in a wide range of climatic conditions and for developing housing that would otherwise be constrained due to expensive construction techniques.

It is a technique that we have been exploring at RISE Design Studio, particularly in our drive to use local, sustainably-sourced building materials.

Build your own home

 

Tens of thousands of people in the UK have built their own home. It can cost a lot of money, take a lot of time to plan and manage, and require a lot more attention to detail than when buying an existing property, but many find that it is worth it to ensure they live in a home that suits their requirements and tastes. In this post, we tell you a bit about what is involved in building your own home so that you can decide whether or not it is for you.

New build architect london

Prepare, prepare, prepare

Self-build properties now account for nearly ten per cent of all private new-build homes in the UK each year. While ‘self-build’ may conjure images of statement ‘Grand Designs’ properties, most tend to have relatively modest designs. This helps the design to receive planning permission and receive funding from mortgage lenders. Mortgages tend to be ‘interest only’, with the borrower paying interest when money is drawn down at the completion of each stage of the build.

A larger deposit than that for buying an existing home is usually required, and additional early costs include buying the building plot, funding planning applications, as well as employing an architect, project manager and a builder. It is ideal to source the architect and construction team via word of mouth, preferably from others who have gone through the self-build process.

Institutional support and finding a plot

As a rule of thumb, building your own home costs £1,500-£2,000 per square metre, although any changes to the original design and spefication during the construction phase can increase these values. Although initial costs are higher than for buying an existing home, there are tax advantages to building a new home rather than extending your current (or an existing) property: new self-builds qualify for rebates on VAT, for example, with the self-builder able to claim back most of the VAT paid on materials. Although VAT cannot be reclaimed on professionals’ fees, nor on household appliances, the average VAT reclaim for one-off schemes is about £13,200.

The Housing Strategy for England (2011) set out the expectation that the number of self-built properties in England would double, with 100,000 to be completed by 2021. In 2016, several legal measures have facilitated more self and custom builds by placing a duty on councils to allocate land for this purpose. Despite this legislation (the Housing and Planning Act), access to land in London remains an issue, as does gaining planning permission and accessing the required funding.

Demolish and redevelop

While there may be few plots with planning permission available, estate agents tend to know about properties that are suitable for demolition and redevelopment. This is likely to be more expensive than buying land with planning permission (i.e. the value of the building is included and there are also demolition costs), but it tends to be easier to get planning permission via this route.

The most important aspect of a self-build project is staying on budget. This requires a project team that estimates the cost of the build accurately and keeps to this quote. A good project manager is crucial in this regard. If you would like to discuss a new self-build project with us, please get in touch.

How much does it cost to build a house?

 

We’re often asked how much it costs to build a house. This is a difficult question to answer: every new build has its own requirements and new build costs depend on a range of factors. In reality, it is possible to have an accurate estimate of the price when all of the drawings and work schedules have been completed. However, there are a number of variables and issues that you can take into account to gain a sense of price before then. We’ve outlined these below.

New build london architect

Location and design

Construction costs vary depending on the location of the site in the country. Central London will be a lot more expensive than elsewhere. For a new build home designed by an architect in London or the South East, current minimum construction costs tend to be in the region of £1,750 per square metre, with land acquisition and professional fees on top of this. Where other issues apply (and we’ll come to these next), this figure is likely to increase to a minimum of £2,000 per square metre.

The design of the property can also have an impact on the cost. It is important to use an architect who has a track record of designing houses that are within your budget (see examples on our Projects page). Where the highest quality finishes are required, the cost per square metre may rise to £4,000 (and more).

Factors that increase costs

It is likely that several other factors will apply to the project which will lead to higher costs. Examples include: party walls; difficult site access; specialist foundation requirements; non-standard forms of construction (e.g. cross-laminated timber); large areas of glazing rather than walls; and high spec kitchens and bathrooms.

There are a number of fees that will also need to be taken into account:

– Purchase costs (price of the sale, solicitor’s fees, survey, Stamp Duty Land Tax);
– Finance costs (relating to any borrowing and associated interest rates); and
– Consultant costs (these will also vary depending on the size and nature of the project – architect, structural engineer, inspectors, etc.).

Factors that decrease costs

There are a number of tax benefits for new build houses which can offset some of the above costs. Stamp duty is calculated on the value of the land only, which is typically less than the value of the land with an existing home on it. Community Infrastructure Levies can be considerable (especially in London) but new self-build properties are usually exempt from this (in line with certain residency terms). VAT is also not payable on the construction costs of a new build house and, assuming the house will be the principle private residence, Capital Gains Tax is not payable if you make a profit at the point of sale.

If you are interested in exploring the cost of a new build project with RISE Design Studio, please get in touch.