Straw Bale Construction

By: Chris Nickson - Updated: 6 May 2019 | *Discuss Tweet

People have built homes using straw, grass, or reed throughout history. During the late 1800s on the American plains however, straw bales houses were a matter of necessity; there was no lumber for construction. Now, with the rise in interest in sustainable housing, there's been a revival in straw bale construction. It's mostly been in the U.S., but in 1995, Bob Matthews, of the Institute for Social Inventions and author of The Complete Manual of Practical Home Building, built a straw cabin in the U.K. (possibly the first such building in Britain) and has been living in it ever since.

With straw often being a farm surplus product and very cheap (around 40p a bale, or £1.50 delivered), it's inexpensive, and an easily renewable medium. Properly built, straw bale houses are fire-resistant, waterproof and actually pest free, with super-insulated walls.

Construction Basics

You'll need about 300 standard three-wire bales of straw to make a 2,000 square-foot house (186 sq. metres). You skewer them on rebar pins (or wood or bamboo stakes) to keep them firm. When you've finished, after adding plumbing and wiring, you seal and finish the walls.

You need to use bales that have a uniform size (about a metre long, half a metre wide), are well secured with two strings, and with very few seed heads. Make sure they're compacted properly and dense - each bale should weight between 16-30 kilos - and dry (and be sure you keep them dry when you're building, for obvious reasons). Even after you've finished the house, you need to be certain the centre of the bales doesn't become wet through either the top or bottom - however, if the outside gets wet, that's fine; it'll dry out naturally.

Types of Construction

Use a "non-structural" or "in-fill" system for bigger structures. That means you make a frame first to support the roof, then pierce the bales with rebar as you rise, attaching the bales to the frame to keep your walls secure.

"Structural bale construction" is a little like Lego, where you stack the bales together in a "running bond" manner. After construction, you simply stucco the exterior and plaster the interior walls. However, since the bales compress as they settle, you need to leave settlement gaps above both windows and doors (how much depends on the number of bales).

Straw and clay construction is a little like cob. You mix clay and water, and then add straw, before packing it into a wooden frame.

Mortar bale construction is similar to working with giant bricks. You put mortar between the bales, and the mortar actually takes the wall's weight (it needs to be quite thick - at least an inch on all surfaces of the bale). It's a good method when you're making a two storey house or a basement. About the only drawback is that the mortar creates cold bridges and thermal leaks. Again, use stucco and plaster to add to the structural integrity.

Finally, there are also pressed straw panels. Here you use straw that's been compacted under pressure. You can also use the panels for floors and roofs if you wish.

Maintenance

In theory, at least, a properly constructed straw house, built where there's good drainage, could last for centuries. You should probably use a different material for the roof, however (something more permanent), and build that roof at a steep angle for drainage.

Foundation

If you're building a straw bale house in Britain, the climate means you'll have to be on a self-draining foundation (one of the best is a rubble trench). You'll also need plastic or metal strapping to attach the wallplate (use anchor bolts) to the foundation.

Make sure your foundation goes well below the frost line, and then fill it with small stones before you put concrete in the rest of the space. You also have to be sure that water can't gather at the point where the bales meet the foundation, which means you need to elevate the foundation by at least 23mm (much higher is better), and leave a good overhang (around 450mm) on the roof.

Finishes

Obviously, after you've completed the construction, you still need to render, or finish, the place. Limewash is good, but very expensive. Earth plaster is an American favourite and durable to use both inside and outside. It's non-toxic, and comes in many colours. Additionally, you have plenty of time to work it and it dries to a hard surface.

Rot and Pests

You shouldn't have a problem with rot as long as you use dry bales. Remember, though, that all the paint must be permeable so moisture isn't trapped in the wall. Believe it or not, you find fewer insects or vermin in straw bales than you do in wood, and once you've plastered the building, they can't get in.

Fire

You might also be surprised to learn that straw bale construction is very fire-resistant; in tests it actually out-performed conventional building materials. However, in spite of all its advantages, getting a mortgage for a straw bale house can be difficult as can insuring it.

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Share Your Story, Join the Discussion or Seek Advice.. [Add a Comment]

Fiat doblo - 6-May-19 @ 2:12 PM I have plenty of general building experience and would like to start building with hay bales I am researching cladding the exterior of our house at present if anyone has tried this? Otherwise can be available for any of the builds posted above. Cheers

Amir - 3-Feb-19 @ 11:42 PM I am trying to build 2 floor Strawbail house in Derbyshire I am looking for some builders that they could do the job it’s existing large farm shade please if you can help me to find some builders

SaSha WarLen - 2-Dec-18 @ 12:52 AM Hi All, Here's hoping I'm in the right place! I am looking to build a 3-4 bedroom Straw Bale House approximately 120 square metres overall (bungalow, dormer or two-storey depending on accepted plans). We are hoping to go with a timber frame instead of load bearing as this would then mean that the build site is covered when the roof is on and the weather would have less of an effect on the bales. I have read that 'one' would normally cost for £1000-£3000 per square metre for a standard build but unsure if this is the same for a Bale Build. I am hoping to do some of the work myself but depending on work commitments it may not be possible so the big ask is are there any builders who work with Bales in the Nottingham area that would be able to give a quote? I have Googled several different phrases but am coming up short when looking for a specific kind of builder and thought I'd just ask! Thanks in advance! Sasha

VJ - 25-Nov-18 @ 12:00 AM Hi I am from Manchester. i am thinking of building small greenhouse withstrawbel wall on North 20 feet and 10 feet on East side with poly-carbonate roof with 45 cm overhang. south side would be glass windows with airflow and fresh air circulating from the roof ridge to grow finger limes and microgreens. I needs an guidance/advice. about the cost - even the possibility of such construction andminimum wall thickness required? If any one out there can guide me - very much appreciated. thank you VJ

Colm Breathnach - 16-Nov-18 @ 4:41 PM Hi there, does anyone know of construction grade straw bales for sale, and can they be delivered to us in County Kerry, Ireland?

Sarah - 9-Nov-18 @ 11:11 PM Hello, i am planning a simple rectangular strawbale home (2 bed, one bathroom, 2 storey, with one downstairs living/cooking spacd) in monmouthshire. If anyone knows of any builders with strawbale experience i would be really grateful if you could pass on their contact details. Thank you! Sarah

Hudsondorset - 4-Nov-18 @ 6:57 PM I’m a builder with a degree in environmental science & policy, and am highly experienced in sustainable living and building. Our team would be delighted to discuss the rammed earth foundations in South Brent. Please pass on my details to Sotuh Brent CLT. Thanks Ian

Davidos - 22-Sep-18 @ 2:07 PM Hello. Im looking into planning for a new plant nursery and we were hoping to have a traditional straw bale type building as a shop and office etc with dimensions of 12m x 6m with a contrasting modern eco buildings as a seperate coffee/farm shop building. Is it possible to construct a building of this size? Also as we are trying to cost all plans at the moment would anyone have an idea of cost? The internals will be pretty open plan as for.shop use so pretty much the shell we need Any help.would be great Thanks

satsuma22 - 19-Apr-18 @ 3:35 PM Hi Archie We’d love to speak to you as we are thinking of building our own house near llangollen and are looking at strawbale but need some guidance :) Thanks so much jane

Berni - 2-Apr-18 @ 11:59 AM Can anyone tell me please the best dimensions including notches and eyelettes for making a resizing needle.

Rachel - 6-Nov-17 @ 5:08 PM Hello, I'm looking for suppliers of good quality straw bales in Pembrokeshire, does anyone have any tips?.We're near Lanycefn and need around 200 for an infill-type bale outbuilding.Any advice for hazel pole suppliers would also be appreciated, and lime plasterers (although I realise the window for lime plastering has closed for the winter). Thanks!

laurabale - 15-Jun-17 @ 6:52 PM Hi, to all those who are building in Cornwall........... I am looking to learn about straw bale builds as I want to build my on house in the future.Id be happy to give my time and limited skills for some teaching, in the cornwall area. Hope this isof interest. Laura

Stratman - 7-Jul-16 @ 10:11 PM We are relocating to Cornwall and hope to enjoy a mostly self-sufficient lifestyle. I am a musician and my ambition is to build a single story straw bale building which will be a guest house come recording studio. My question regards planning permission and the chances of getting planning permission to do this. Does anyone have any experience of a similar project? Any advice, tips, would be most gratefully received. Thanks

landd - 26-May-16 @ 6:25 PM Hello We are building a straw bale house in the Correze region of France. I need some advice as to where to source straw bales in France. Can anyone advise me? Thank you for your help L

Archie Mac phearsum- Your Question: I am a straw bale lime plasterer and like to advice on the plastering to straw so their is no failure I've been strawbale nut for a over 20years and a recording studio is a great idea please contact me if need advice on lime plastering onto straw I have done a lot of strawbale projects Our Response: Thanks Archie, I've passed on your email address to the original poster hope that's OK. SustainableBuild - 22-Apr-16 @ 12:16 PM Thanks Archie, I've passed on your email address to the original poster hope that's OK.

Archie Mac phearsum - 21-Apr-16 @ 12:48 PM I am a straw bale lime plasterer and like to advice on the plastering to straw so their is no failure I've been strawbale nut for a over 20yearsand a recording studio is a great ideaplease contact me if need advice on lime plasteringonto straw I have done a lot ofstrawbale projects

Gordon - Your Question: We are planning new music studios in SE London, and considering creating two large straw bale buildings –1 x 16mt x 11mt internal space, and the other 1 x 10mt x 7mt, both as a two storey build.We are practical, with wood working and building skills, so we could help as part of the construction team, although we will need one or two people with straw bale building experience to lead the project. The planned site is a yard and has a good solid concrete base 30/40 cm thick pretty much throughout. Not sure its self-draining however. Load in for materials is good and direct to site, with easy access for trucks & fork lift. This could be a very interesting project, so if anyone has suggestions on how to progress this plan further, please get in touch.Many thanks Our Response: If anyone wants to respond via the SustainableBuild team, they can send in their details to jmarshall@pts.com and we'll forward them on. SustainableBuild - 21-Apr-16 @ 11:22 AM If anyone wants to respond via the SustainableBuild team, they can send in their details to jmarshall@pts.com and we'll forward them on.

Gordon - 19-Apr-16 @ 5:36 PM We are planning new music studios in SE London, and considering creating two large straw bale buildings – 1 x 16mt x 11mt internal space, and the other 1 x10mt x 7mt, both as a two storey build.We are practical, with wood working and building skills, so we could help as part of the construction team, although we will need one or two people with straw bale building experience to lead the project. The planned site is a yard and has a good solid concrete base 30/40 cm thick pretty much throughout. Not sure its self-draining however... Load in for materials is good and direct to site, with easy access for trucks & fork lift. This could be a very interesting project, soif anyone has suggestions on how to progress this plan further, please get in touch. Many thanks

julie - 13-Apr-16 @ 10:00 AM Hi x I have an old stone wood barn x I am looking to renovate it using straw bales, into a space for yoga and therapy x Do you know anyone in devon who would have some knowledge on straw bale building x thanks julie x

strewbarn - 20-Feb-16 @ 5:53 PM I am thinking about doing a barn conversion. The barn we are looking at is quite small so I would like to double it's size both downstairs and upstairs with a strew bale extension. Is this possible? Would it be possible to put one roof on the building? Thanks

SustainableBuild - 12-Feb-15 @ 2:08 PM @Starman - we'll put this on our facebook page if you like.

starman - 9-Feb-15 @ 10:52 PM Hi, I hope you can help...I'm looking to find a supplier of construction grade straw bales in Cornwall. I have not been able to find any so far and I'm losing the will to live! Failing that, could you recommend a supplier that could also deliver to Cornwall? I look forward to your reply, Starman.

k lewis - 30-Jan-13 @ 10:38 PM Hi I was wondering if anyone could help me with a topic im trying to do with my dissertation. The topic so far is based on whether straw bale construction has a major impact on sustainability? Is there any links you no that could help me with this research? Regards,

Syeda - 21-Dec-12 @ 11:40 AM Hi I have a bisf property and have recently discovered that the ceiling has been insulated using straw I wanted to put spotlight on in the ceiling but am conscious about fire hazards is it possible to install spotlights within a straw insulated ceiling

Jimmy - 29-Oct-12 @ 6:37 PM Hi - I have an off grid water access property near Parry Sound Ontario. I will be building a 32' x 24' log & stick frame cottage in 2014 and am looking into "Sustainable Building" ideas-- I am thinknig of using straw bales only for the foundation - is this possible - the site location is high and dry - Thanks - Jimmy

Bass - 28-Oct-12 @ 2:38 PM Can you recommend a builder who could build me a straw bale extension to my home in London? Thanks

David - 4-Oct-12 @ 10:53 AM As the article states, you do need the right ground, and insurance will generally be problematic. You also need to be extremely careful not to construct the house in an area that’s prone to flooding and it would generally be destroyed, or at least rendered uninhabitable. If consider a straw bale house, take this into account.

oli - 3-Apr-12 @ 11:44 AM Hi Chris, I am working on research relating to the chronology of straw bale construction at the moment and I was wondering if you have any images of Bob Matthews' house or if you know a good way of contacting him? Haven't had much luck Googling 'Institute for Social Inventions' unfortunately! Any clues/leads greatfully received . . . Thanks, Oli

Dan - 27-Feb-12 @ 2:10 AM Interested in finding Areas that Are excepting Strawbail construction a Directory Ect.. Building Law.

Carole - 19-Sep-11 @ 2:29 PM Hi, I'm interested in the response to jonneve's question as above, as I too want to add a straw bale construction to an already existing block wall. What is the best way to tie them in, given that the bales will compact somewhat ( it will only be a single storey and not very high) and just 32sq metres to mirror the existing building.Thanks for any help,Carole