Why I don’t use cement in my designs

I am often asked to help with other people’s designs, but one of my principles is never to design with cement. Not everyone knows this about me, and I was recently asked what my general experience was with stem walls made of concrete (cement plus aggregate), what are the things to consider or the possible problems with building strawbales on them. My client went on to say “most of the straw bale builders or straw bale building companies I’ve observed so far in the internet use concrete for their stem walls!? So it seems to work?”

Hmmm. Just because most people do something doesn’t mean it works, or it’s a good idea. This does highlight one of the major problems with cement though, that the problems it causes are not visible or apparent straight away, in fact they can take many years to become obvious. I myself was educated in the use of modern materials and techniques as part of my learning in the construction industry, and I thought, as most people do, that foundations had to be made from cement and bricks had to be laid with a cement mortar. So I know how to lay cement floors and build brick and stone walls, and have done many in my time – but all fortunately now a long time ago.

As I began to learn about natural materials in the 1990s, as well as strawbale building I studied lime and clay plasters, and cob building. I also had an interest in old houses, and I realised that all our old houses (built before 1900) are built entirely of natural materials, and in fact all old houses everywhere around the world are too. This shows how unbelievable it is that anyone could think that natural materials aren’t durable – but we are all prey to thinking that what everyone does now is better than what people did in the past. There is a common misconception that cement has replaced lime and clay because it does the job better, but I digress…

A major problem with cement and concrete is that it attracts or ‘wicks’ water. If you put a concrete block in an inch of water and leave it for a couple of days, the whole block will get wet. If you stand a piece of wood (or a strawbale) in an inch of water they will both become wet to slightly higher than an inch but no more. They do not wick water. So, using cement for mortars and renders means that when it rains the cement brings the moisture through itself to whatever is behind it. Usually, when it stops raining, most of this dries out again, but not all, and not in damp conditions, or where there is moisture present most of the time.

In cement foundations, the cement is in contact with the wet earth, so standard practice is to protect the building above from the wet cement by using a damp proof course. More importantly, external walls always contain a certain amount of moisture, due to external rain and internal occupancy (hot showers, cooking etc). In buildings built with cement mortars, this moisture is increased as rain penetrates through the mortar joints. This moisture always travels downwards because of gravity and ends up at the base of the wall. Again, standard practice is to use a cavity tray damp proof course, to direct internal moisture towards the outside of the building. The main reason that people do not realise that cement is actually increasing the moisture content of the building is that the movement of moisture happens very slowly. It can take 30 or 40 years before problems begin to show, which will take the form of moisture build up at the base of the wall, eventually showing as damp problems internally.

When these problems due to the use of cement first started to show, the industry said it was caused by rising damp, and the chemical injection of houses against damp was invented. In fact we now know that there is very little incidence of rising damp, and most damp problems are caused by other things. The Society for the Protection of Ancient Buildings (SPAB) has some excellent research and information on this subject.  See http://www.spab.org.uk/advice/technical-qas/technical-qa-20-rising-damp/ Another trend that began was to re-point houses with cement that had been built with lime, and to repair old lime renders with cement renders. No-one knew this was a bad mistake for many many years, because the problems it caused took that long to show. It wasn’t till the spectacular collapse of several cob buildings that had been cement rendered that we started to understand that cement was damaging our buildings, particularly our older ones that were built of natural materials. Today, English Heritage has banned the use of cement on heritage buildings for this reason.

Many modern buildings suffer from condensation problems, and this is a direct result of using cement blocks, mortars and gypsum plasterboard, although this is also because of another of their properties, which is impermeability, they prevent the passage of vapour. Lime and clay on the other hand actually regulate humidity and can hold excess moisture within themselves without becoming ‘wet’ and release it as humidity levels drop – they are hygroscopic. This also helps to keep indoor air quality healthy. Lime used as mortar or render outside absorbs water when it rains, and as it becomes saturated this actually prevents moisture passing through it and so it protects the building behind it. When it stops raining, this moisture is released into the atmosphere.

So I return to my client’s question. The fact that so many people use cement does not mean that it “works”! It simply means lack of awareness. Most people are not designing for a 200 year life, as we do. What we see is that houses built in the 1970s (out of cement) are being pulled down and deemed not fit for habitation, when houses built by the Victorians or earlier (cement started being used widely in construction after the first world war) are being renovated (oh no, often with cement) and continue to give good service… until the effects of new gypsum plaster or cement pointing start to cause damp or condensation problems.

Finally, there are many ways to build foundations that do not require cement. All our old houses have foundations with no cement – how could they be otherwise? I have designed several types of foundations that do not need cement, these are available for anyone to use on our website in the Free Information section. All these designs are legal, are approved by Planners and meet current Building Regulations.

I recommend everyone to begin to understand the wonders of lime and clay. I expect that if you do then like me you’ll want to become a Natural Builder!

If you’re interested in learning more about cement and what causes the problems it suffers, here are three blog posts I’d recommend:

http://surveyingproperty.blogspot.co.uk/2014/11/concrete-part-1-understanding-basics.html#.VGyGQvmsWxI

http://surveyingproperty.blogspot.co.uk/2014/11/concrete-part-2-carbonation.html#.VGyGWfmsWxI

http://surveyingproperty.blogspot.co.uk/2014/11/concrete-part-3-understanding-basics.html#.VGyGb_msWxI

Building for Sale

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This wonderful building is suitable as an office, a guest room, a teenage crash pad, a studio etc. and can be located in your garden or near your premises, subject to suitable access. It can be used all year round as it’s made of straw and is therefore highly insulated.  It will keep you warm in winter and cool in summer without the need for any heat, as long as you face it south.

The building externally is 4.2m long x 3.2m wide and 3.2m high, giving an internal area of 7m2, with 2 windows and a French door. At present it is unfinished. It can be bought as is (see pictures below) for £17,500. This price includes these extra materials: clay for finishing off the internal body coat plaster, French doors with all the door furniture, 4 x double sockets, 1 light switch and beautiful Douglas fir for external finishing boards. You will also need 4 tubs of lime render body coat and some lime render finish coat. The roof covering requires a downpipe to be added on both sides and a build-up of planted sedum. You may also want an internal top coat of clay depending on your aesthetic choice of finish. The building will require a raised foundation. Delivery is extra to the price.

If you’d prefer the building to be finished, Straw Works can do that for you by completing the work mentioned above including simple foundations. The finished price would be £24,500 + delivery.

This building was transported from the Grand Designs Live exhibition in London on a low loader to Suffolk where it is residing temporarily. This is the first time a strawbale building has travelled this way! 

If you are interested in knowing more about this building please contact Eileen at strawworks@gmail.com or on 07857 890805

Straw Works needs your help!

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We will be building a real building at Grand Designs Live this year. We didn’t have much notice and are having trouble finding a strong enough trailer to build on and transport our building once it’s finished, plus an HGV vehicle to move it. Ideally we’d like to plaster our building, which means it will weigh about 5 tons when finished. Can anyone help us? Sponsorship or reduced costs would be great. We can advertise you on our website and give you tickets to the show..

http://www.granddesignslive.com/component/content/article/65-grand-village-homes/1279-straw-works

If you’d just like to sponsor us anyway, please get in touch with Jane at strawworks@gmail.com Thanks!

These natural building companies have already sponsored us – a very big thank you to them!

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More strawbale social housing!

Congratulations to Hastoe Homes for their 4 new strawbale houses in High Ongar, Essex! They look remarkably similar to the ones we designed for North Kesteven Council in 2008 – see the picture of ours below:

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The pair of semi-detached loadbearing houses at Martin, Lincolnshire, were designed by the Straw Works team (working as amazonails) and built in 2008/9 by Carter Homes.

The main difference between the Hastoe homes and ours is that (of course) ours are loadbearing and theirs are infill, but they still look great. And they share the same fantastic environmental credentials: negative carbon footprint, very low running costs (cos they’re so well insulated), made from natural materials – everyone who has one loves it.

So if you want us to design one for you – just get in touch at strawworks@gmail.com – we do a nice line in all-year round beautifully organic garden buildings too – ideal for a home office or studio.

And if you want to read more about the Hastoe homes see here: http://www.homesandcommunities.co.uk/news/hastoe-strawbale-housing-officially-opened-eric-pickles

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Women are full of common sense

Women are full of common sense – we prefer to work with natural rather than unnatural materials

I’ve got the chance to blog on the Huffington Post since being short listed for the First Women Awards this year, hosted by the Lloyd’s Banking Group. I’m new to this, but want to approach it in the same spirit of adventure that all the women new to strawbale building bring to my courses. The statistics for women ‘on the tools’ in construction – that means actually doing it rather than managing or supervising – is pitifully small. And even more of a shock, haven’t changed since I trained as a carpenter and joiner over 30 years ago. There are still less than 1% women doing manual work on our building sites….

I find this hard to believe. Hard because what on earth has our government and the CITB and the construction industry been doing about it all these years, and hard because I absolutely love my job, and can’t understand why there aren’t more women out there doing something similar.

Which brings me back to courses: my company, Straw Works, runs practical training courses on real building sites. (We do a lot more than this too, designing and building houses, studios, visitor centres exclusively from natural materials). Most of our trainers are women, and 50% of our course participants are usually women. So how come we can be so spectacularly successful and the construction industry as a whole so despairingly a failure?

One of the main reasons is that we create an environment that is conducive to learning and welcoming to women as well as men. Early on in my career I realised that if I didn’t create my own working environment with my own values and ethos, I’d have to stop doing the job that I loved because I’d be coping with other stuff that shouldn’t be part of my working life – girly calendars in the office, chivalrous men taking my tools off me and doing the job for me, macho flouting of health and safety guidelines, and other things far worse. Most women who train in construction end up working for themselves if they survive at all, due to the atmosphere found on most building sites.

I’ve been determined to create a working environment for myself and my colleagues that reflects my values, of cooperation, team working, high quality work, enjoyment of the job and the process, and the feedback I get is that I’ve achieved it. Many women who have never done any practical work come on our courses and learn how to build with straw and to plaster with clay and lime, and love it! They come back for more!

There are many reasons why women come on our courses, but one of them is that we offer the chance to work with natural materials instead of unnatural ones. I have long suspected that women are full of common sense, and this proves it – given a choice, women prefer to work with straw, clay and wood than with cement, plastic and fibreglass.

Other obvious reasons, though, are that we have women trainers, and this sends out the message that we are welcoming to women joining our courses, and that we understand that women have different training needs to men. We don’t ask for any previous knowledge, or access to tools and equipment – we provide everything that’s needed. And our courses have a reputation for being fun and interesting – many people, women and men, come back for more!