Integrated Design Feedback

Hello

I've been interested in Permaculture and owner built off-grid design for a long time but I feel like I have to try something, the sooner the better.

The total floor space is 400sqft (20'x20')
I approached my design from an integrated perspective in order to minimize not only the size/cost of the house, but also the need for any additional furniture/accessories. Of course, the design is never complete, but I wanted to get some feedback as to whether I'm crazy or not.

I know there may be code issues that will need to be addressed, and I would like to locate architect/engineer who is familiar with Straw Bale construction, but I'm wondering if there is something about my design that is just not possible to translate into the real world?

I used the 3d Builder tool that came with Windows10 (I know, it sucks) to visualize my design, and it has gone through lots of evolutions. Attached is my current design, and I know I'm missing some elements, but I was hoping someone can give me some constructive criticism that may challenge me.

The stove in the middle is based on the Walker Continental Stove, but I'm flexible as to the type/size of the stove, it was just the easiest one to model simply, and I like the features/cost ratio.

The counters, bench, and bed platform would ideally be made of rocks/rubble mortared in shape and plastered with the same lime as the walls. The counter areas near the sink and the bathroom would be tadelakt for water resistance. The sink could be integrated as well, but I'm ok with using a regular tub sink.
The bathroom may need some work, as I may put a bathtub in. The storage cabinet that separates the bathroom from the main room provides the majority of the storage, along with the many shelves along the wall. The box in the corner under the shelves represents the small photovoltaic battery/inverter equipment, as the electrical will be very minimal as there is no fridge and I would rely on dehydrated/canning food for preservation.

Any feedback would be greatly appreciated.
Thank you.

<I tried to upload the .3mf file but it isn't allowed. Here is a link to it>
https://drive.google.com/file/d/1v3rJdSvfiQCzKx-yyPbuv5GBUWjNzzWX/view?usp=share_link

Hi Gary,

I applaud your effort to keep living spaces small!  IMHO, this is the "holy grail" quest for affordable, energy efficient and mostly natural code-level housing.  

You don’t say where you’re building, but if in the United States you might find some of this useful.  I wasn’t able to download the file you posted—if you can add a few more images it might help clarify things.

The trade-off with wall assemblies that use mostly natural insulative materials like straw bales, light-straw-clay, hempcrete, blown-in straw, straw panels, etc., is that in most cases you need thicker walls to achieve code-required wall insulation.  The building footprint of a structure that uses these natural walls is often somewhat larger than buildings using more conventional wall systems, and most building departments measure a structure's footprint from the outside surface of the exterior walls.  This has both permit cost and property tax implications.  A 400 sq. ft. straw bale building with 15" thick walls (plus 1” + of plaster on both sides) has a bit over 300 sq. ft. of living space.  A few building code jurisdictions recognize that structures that go beyond code-minimum could be rewarded instead of punished and waive this interpretation, instead counting the interior square footage plus 6” of the exterior wall when they calculate the building’s footprint.  

Last summer my crew built a permitted 400 sq. ft. straw bale building (exterior measurements) that is now a music studio.  However, with minor (and expensive additions, like plumbing!) could have been built as a small living space for one or two.  The design team was guided, in part, by the building code pertaining to tiny homes.  

Follow this link to view the code: https://codes.iccsafe.org/content/IRC2018P5/appendix-q-tiny-houses.  This is one of the model building codes that code jurisdictions can adopt, and if they haven't, that homeowners in the United States can use support of their permit application under the alternative materials and methods provision of the building code.  

The design was also guided by a desire for the structure to be passive solar.  The winter sun keeps the building comfortable, and the south-facing roof overhang and super-insulated ceilings and walls keep it cool in summer. Still, it has a small mini-split for both supplemental heating and cooling, but the unit doesn't work very hard since the walls, ceiling, and floor are insulated well beyond code requirements for our area.  

Another building code you might look at is Appendix S: Strawbale Construction, which is available as a free download from the California Straw Building Association, http://strawbuilding.org.  While you’re on that website you might consider purchasing CASBA’s Straw Bale Building Details: An Illustrated Guide for Design and Construction, which also has Appendix S printed in it.  This book won’t describe how to lay out a floor plan, but it will explain the many ways to build a straw bale wall and discuss the trade-offs inherent with design decisions specific to straw bale walls.

As for finding design professionals familiar with straw, you might click on CASBA’s “resources” when you visit the site—there are quite a few architects and engineers listed there, and many take on projects outside of California.

I’m not a designer, but during my building career I tried to influence designs in order to make the structures easier and less costly to build, take full advantage of the straw bale wall thickness, and make the buildings more livable.  Not sure if you have long or short winters, but the smaller the conditioned space, the more you may want to have large outdoor spaces like porches and patios.  A covered porch that functions as an outdoor room makes tiny house living much easier.  Also, use window seats where possible—these can replace a few chairs or a couch without taking up floor space.  And be careful with what you expect of lime or clay plasters.  They are best used on vertical surfaces (walls), but wear poorly on horizontal surfaces like window stools, window seats, counter tops, etc.  I have done a lot of repair work on lime or clay plastered window stools, seats, and counters—use more durable materials here, like wood, or tile, or stone.

RE: wood stoves.  When you have a well-built, super-insulated structure you can downsize the heating and cooling systems. For example, a stove rated to heat a 1000 sq. ft. space will quickly overheat a well-insulated, air-tight 1000 sq. ft. space.  It’s not a bad idea to make the structure as air-tight as possible, too, because leaky buildings will carry heat in and out regardless of how well insulated they are.  

If you can include more images of your project I may be able to offer other thoughts.

Jim Reiland
Many Hands Builders

Hello

Thank you so much for taking the time to answer. I should have stated that I am in Canada, Ontario more specifically. I think a lot of your advice still applies, and I agree that I will probably have to look for someone local that has experience with strawbale.
I hadn't considered that the total footprint would be the one used for code/tax purposes, so thank you for that as well. The design I posted is designed for 400sqft interior, and with 18inch thick walls so approximately 529 sqft total (I hadn't realized it was that much!)

Good to know about the limitations of lime on horizontal surfaces. Maybe some sort of inset granite slabs in high wear areas.

For the stove, I agree totally, that was my goal, to use a little wood as possible to heat/cook, and to take advantage of outdoor areas when possible. The less wood needed to haul, the better. The stove I used in my design is the Walker Continental, which I haven't seen much about, but it says its for ~1200sqft, so I figured I may have to open the door somedays to cool off the house a bit if needed.

I think my main reason for sharing my design is that I don't see a lot of houses that incorporate the furniture into the house itself, which to me seems obvious, but I thought maybe there is a practical reason why it doesn't seem very common, that or I am just weird.

I was thinking about a shed roof, but now I'm not sure. I would appreciate any suggestion you may have for choosing one over the other regarding cost/ease of construction?

I've attached some more photos in case you can't view the 3d file.

Here is another link to the file: https://www9.zippyshare.com/v/QFb40EKg/file.html
The file is in .3mf format, so if you have access to a windows 10 PC, you can install 3d Builder from the MS store (free) if it's not already installed.

Again, thank you for your time

Its funny Gary, I am a pen and paper designer.
I can visualise the 3 dimensional shape from a 2 dimensional drawing.
I have seen furniture created from earth and of course the Rocket Mass Heaters discussed here very often are often built from earth.
You speak of a 'shed roof', I imagine you are speaking of the light weight structures used on sheds.
If you are building to code you may be in strife, but if its a shanty built place they are easy to build.
Good insulation can be difficult though.
If you think about the roof, there are a variety of methods to use and some can be built using trusses made from short bits of material you may find free of charge.

Gary said, "I was thinking about a shed roof, but now I'm not sure. I would appreciate any suggestion you may have for choosing one over the other regarding cost/ease of construction?

I am wondering if you are trying to figure out what kind of roof to add to your building/shed.

This Wikipedia explains the different roof types:

https://en.wikipedia.org/wiki/List_of_roof_shapes

Are you looking to do something like a single-pitched roof?

Or are you asking about roofing material as to whether to use metal or shingles?

Here are some threads that might interest you or others:

https://permies.com/t/155527/Material-Shed-Roof

https://permies.com/t/189786/Seeking-advice-attach-roundwood-rafters

"Shed roof" in the US (and Canada I presume) means a single-sloped roof shape. It has nothing to do with construction materials or method. I understand in Australia and perhaps some other places it is referred to as a "skillion" roof.

Hi Gary,

RE more local assistance.  If I were building in Ontario I’d contact the Endeavour Center in Peterborough, ON.  Chris Magwood and Jen Feigin are a wealth of information about straw bale construction in your region and climate.  They, along with Jacob Deva-Racusin with New Frameworks in Vermont pioneered a hybrid wall system sometimes referred to as a “straw-cell” wall assembly that adds a framed cellulose wall to the bale wall in order to move the dewpoint out of the bales.  The CASBA book I referenced in the email above gives this wall assemble a page and a paragraph, which really doesn’t do it justice (the challenges of publisher page limits and books about complicated subjects!).

Footprint.  It’s worth calling your building department to find out how they measure square footage.  There are just a half-dozen jurisdictions in the U.S. that use interior measurement plus 6” (the typical conventional wall width) when making that calculation.

Built-in furniture. You may be weird, but no more than I am.  I think there are a couple of reasons why we don’t see this very often in modern house designs.  First, new homes in the US (and Australia!) average somewhere around 2500 sq. ft., which is roughly 2 ½ x larger than the world average (900 sq. ft.+).  This happens to be about what the average home size in the US was in the early 1950s.  I don’t know what caused the shift—family sizes have been getting smaller--but we all have a lot more stuff?  Just saying.   Anyway, built-in furniture is usually crafted by finish carpenters, and they’re at the high-end of the pay-scale in housing construction.  That raises housing costs. That, and many people want the flexibility of arranging furniture to suit their needs.  With the drive to keep housing costs down and keep floor plans flexible, I’m not surprised that built-ins are...well, out.  When it comes to much smaller structures it makes more sense to have built-ins—there are a lot fewer ways to arrange seating around a table, or a wood stove, etc.  Again, when you’re working with thick walls, you might as well take advantage of the space they consume by converting window stools into window seats.  Most window frames take up 6” of space, so with an 18” wall you’ll need to build a bench out around 6” beyond the wall surface so your seat depth is at least 18”.  We discuss this in the CASBA book, pages 37, 38, detail 2-20a.

Shed (or Mono-Pitch) vs. Gable Roof.  Around here the term "shed roof" is used interchangeably with "mono-pitch" roof.  Tradeoffs: if you’re building on a site exposed to wind-driven rain and are averse to working on ladders and scaffolding I’d recommend a gable roof.  The walls will be shorter, easier to stack and plaster, and with large overhangs, better protected.  But if your site is sheltered by surrounding woodlands or topography definitely consider a shed roof.  You’ll have more space for a loft, but the gable walls and one eve wall will be considerably taller, which is more difficult to stack bales into and plaster.  
 
A related question is the type of roof framing, which needs to account for both the span and wind/snow loads. In smaller buildings its tempting to use 2x lumber, e.g. 2 x 10s or 2 x 12s for rafters, but there are a couple of down sides.  Large dimension lumber comes from larger, older trees, and even with a 2 x 12 you may not have enough depth in the rafter cavities for the insulation plus a ventilation space you’ll probably need in your area (unless you insulate with spray foam or rigid foam, which I can’t recommend due to their high environmental cost.  They might work with an unvented roof design, depending on which insulation you go with.  For a gable roof you could use scissors trusses to give the space more ceiling height.  Parallel cord trusses for either a gable or shed roof would create the same effect.  Both may cost more  than 2x rafters, and if you make them yourself will definitely require more labor, but they use small diameter trees and allow for better insulation and less thermal bridging.  You could also use I-joists, but note that batt insulation doesn’t fit tightly between the I-joist webs unless you fuss with it.

Good wearing surfaces.  Stone is certainly an option.  Poured-in-place concrete and tile are also popular. A lot of my clients are keen to keep their environmental costs low since building a house—any kind of house—is among the most environmentally costly things we can do, so  I recommend a local wood, which for us in S. Oregon is Douglas fir or Big Leaf maple, though almost any wood will be more durable than lime or clay plaster for a seating or shelf surface.

Jim

Gary Cooper wrote:

I was thinking about a shed roof, but now I'm not sure. I would appreciate any suggestion you may have for choosing one over the other regarding cost/ease of construction?

At 20+ feet a shed/mono slope/skillion roof will give the house kind of a stark industrial look. Our house is 16 feet wide with a monoslope roof. We built a wrap around porch that breaks up the high wall. The high wall of a 20 foot wide house with a mono slope roof  would also be 16+ feet tall. For simplicity I would go with a gable roof. For slightly more complex but more interesting I would do split level roof with clerestory windows.

I build a lot of Skillion roofs here in Australia.
Mainly because it means I have only one edge to collect rainfall from for use in the house and on the garden.
They can be built in a 'truss ' plant and carted and lifted into place easily, but I have always made my own from recycled timber.
It is time consuming, and insulation needs to be fiddled with, but smaller bits of timber can be used / found.
If large spans are required DIY can be troublesome, but clever design will go a long way to limit that.
I have built many with scrap steel by using angle iron, 2 x2 x 3/16 inch
Sometimes timber trusses have ring set in around bolt holes to spread the loads better.

Water = Cistern or Sand Point Well or Spring or Deep Well or City?
Septic = Composting Tiolet or Aerated IBC Tanks Setup or Regular Septic or City
Electric = Off-grid Solar, 3kW Solar Array, 10kWHr Battery Bank, 12kW Sol-Ark Inverter??
Domestic Hot Water = 5kW/ 1gpm Tankless Electric Hot Water Heater
Heater = Radiant in Floor Heater,  500ft of  pex-pipe, circulating pump, heat-source or RMH
AC = 2kW Mini-Split
Ventilation =  30cfm ERV
Doors = 3ft wide (great for aging in place)
Foundation = Pier & Beam or Slab or Rubble Trench or ???
Roof = Solar Panel or Green Roof or just paint it white

balecob wall, from the ground up, has:

Rubble trench. This foundation of loose stone, gravel, or “rubble” in a trench under the walls will provide support and drainage.
Stem wall. A short wall of stone, earthbags, concrete, or other rigid, impermeable materials will bridge the rubble trench and the vertical walls, and protect the walls from water.
Base cob layer. An 8- to 10-inch-thick layer of cob on top of the stem wall will even out any inconsistencies and make a smooth base for the straw bales.
Bales and cob pillars. Straw bales make up the bulk of the wall, with cob “pillars” at the corners and intermittently in long walls for structural integrity. Gaps between bales are jammed with cob to hold the wall together and compress the bales.
Top cob layer. The final layer of cob, typically at least 1 foot thick, will compress the bales further and provide a firm connection to the roof.
Roof. Rafters are tied into the final cob layer, making the whole structure more stable

https://www.motherearthnews.com/sustainable-living/green-homes/natural-building-with-balecob-zmrz18fmzgsch/

Let me know what you think of this floor plan.

S. Benji, where you have the hall to the bathroom could you eliminate that and include some sort of cupboard / linen press in the space?

Having two exits is sometimes required to pass code, so I left it so that a door can be put there if needed.
It is possible to move the bathroom door but then the wet wall with the plumbing would be against the outside wall and that increases the odds of the pipe freezing.

By having that door it is also possible to add another unit, either as an replica, so that it would be a duplex or it could be an addition so that it becomes a 3bedroom.

Fair call, a future extension is always worth planning for.
You speak of the wet wall freezing, thats not an issue here.
Sometimes though the cold pipe gets the sun and its almost boiling instead if being cold!

In downsizing my house and looking at tiny home living, one of the furniture pieces I was looking at online was a Murphy bed unit that had a fold-down table built under it.   So you'd put the bed up,  fold down the table, and having dining/work space during the day.   Fold the table up and pull down the bed at night.   A few units had nice small closets units or bookshelves to either side as well.    Was a nice way to have the same space serve different functions.  

(also I thought it was a good way to not have to sacrifice bed size too much either)