Eco Foundations – Plynths and Screwpiles

When it comes to building a new house, foundation is probably the most difficult and eco-unfriendly element of your house. Still, it is so important that you simply cannot afford to get it wrong. Concrete slab foundation is certainly the most popular of all foundation types.

From a perspective of an eco-builder, the slab is not a particularly attractive thing. The downsides of concrete slab foundation are:

• It takes a significant amount of groundwork to prepare for laying the slab.
• Production and hardening of concrete is very carbon-intensive. The less concrete you use, the greener your house is. Each ton of cement manufactured causes one ton of CO2 emitted into the atmosphere. Each cubic yard of concrete poured in a foundation contributes 630 pounds of CO2.
• You are limited if building around large trees. If they are listed trees, no-one will give you permission to cut them or damage the roots. With screwpiles (sometimes called helical piles) you can easily maneouvre around the roots.
• Get it wrong and you’re in big trouble.
• It takes a long time to go from measuring up to a complete foundation.
• Insulation challenges – if you’re building in a damp spot and fail to insulate the slab properly, the house will forever suffer from dampness, mould etc.

The Beauty of Screwpiles

There is a good old method of making foundations. Despite being around for 180 years, it is still regarded as controversial. Screwpiles – long steel piles with multiple lateral bearing plates. The method was developed in England in the 1830s. The first structure to have a screw pile foundation was the Maplin Sand lighthouse at the mouth of the Thames. It was built in 1838.

Now screwpile foundations are widely used by key industries (pylon foundations, masts, wind generators) but the truth is that screw piles can support a significant amount of building mass, therefore can be used in building houses. I don’t have to go far for an example – the Bournemouth Pier was built on screwpiles – and it is an enormous structure with several buildings on it.

Installing screwpile foundations is an easy and quick process. Just measure it up, screw them in, add joining brackets and attach the frame (wooden or steel) to the brackets. However, it takes skill to do it.

If we only consider the cost of material, it will be cheaper to purchase the necessary load of concrete than to obtain screwpiles, but then you should consider other factors as well. A screwpile foundation can go in as quickly as few days whereas it will take weeks to complete a slab foundation. You won’t have to fret about groundwork and soil disposal – so, in the end a helical pile foundation can be cheaper than a concrete one. Besides, you save time.

Another Type of Eco Foundation – Plynths

If building small houses, consider plynth foundations. Their application is limited to steady soils and wooden frame buildings. You cannot build on dodgy grounds or using brick and mortar. However, if it is a wooden building you’re after, plynth foundatons will save you loads of time and money. The method is invented and promoted by Swift Foundations of North Yorkshire.

They’ve recently completed a foundation for Broxbourne Sailing Club in Essex. The 135 plynths support a huge 3500 sq-ft timber frame building. Going for Swift Plynths has saved the Sailing Club 60% off the usual foundation costs. Not bad, eh?

How about Concrete then?

Then there are the conventional piles made of reinforced concrete. This is not an entirily green approach because you’re still consuming concrete. However, compared to a concrete slab foundation, you will use only a fraction of concrete with the piles.

A normal size family home will need only a few concrete piles. On top of them you can mount a steel frame for your house. Concrete piles, if installed correctly make for an extremely strong foundation. They get support from both end bearing (their tip pokes onto a harder layer of soil) and skin friction (stops soil from moving around the piles).

Yes, you will need heavy machinery to install concrete piles but consider this:

• Little or no groundwork
• Piles come pre-fabricated from a factory.
• Less workforce required
• A relatively quick way to install foundation
• So, again, if you plan it properly and shop around you can get your foundation cheaper and quicker. Time is money on a building site. So why wait for the carbon-guzzling slab to harden if you can get your house up much quicker?

These aforementioned eco foundation alternatives are especially favourable if you’re building a wooden frame house. Please note that there might be rare situations where you cannot but go with the conventional slab. A proper soil examination is essential if you want your house to last.

Pics by:
http://www.screwfast.com
http://www.maltech.co.uk
http://www.newportunlimited.co.uk