Build roof first for Hyperadobe?Hiperadobe(Portugal) Earthbag house?

Greetings all earth bag builders,
I'd like to make an oval Hyperadobe house - probably around 60-70 foot long.

What do you think about building a timber-framed (reciprocal?) roof with timber supports first, then building up the Hyperadobe walls underneath?

The idea is to leave the roof space directly above the wall uncovered at first, for clearance to walk and tamp the bags down.
My thinking is that I can rig a tarp over the frame to quickly cover the build in case of heavy rain, or if I need to leave the build for any length of time.
I may also be building in high temperatures, and a tarp could prevent the hyperadobe layers (and floor) from drying out too quickly?

Once the wall is finished, I plan to finish the roof, render the walls, and then do a cob/glass bottle infill to seal the gap from the top of the wall to the underside of the roof.

1)  Build roof with 4 foot overhang for a wrap around walkway/verandah... edges of roof supported by sturdy poles
2)  Dig foundation trench, then do a tamped earth floor, followed by Hyperadobe walls
3)  Seal with bottle-wall/cordwood/cob infill.

I guess my questions are - does the Hyperadobe wall need the weight of the roof compressing it to make it strong enough?
- Should I do the floor before I build the walls?

I've read loads, watched a ton of videos..... it's all just a hypothetical jumble in my head right now.
I feel ignorant, but eager to learn and finally build my own natural house.

Any thoughts? Advice?

Thanks,
Cath

Generally speaking, one builds from the ground UP, not the other way around.  I'm not sure I see the benefits of building in the opposite direction.

Foundation first

Walls next

Roof last.

The reason is simple.  Each piece supports the next piece above it, and you don't have a roof getting in the way of building a wall, and you won't have a wall interfering with the building of a foundation.  

What you're proposing seems to be a LOT more work, and with little benefit.  So I ask, WHY do you want to do it the way you propose?  What's the benefit in that?

Well, is hyper adobe load bearing?
Some adobe is just used as in fill.
Certainly a dry place to work and store materials would be good.
If a "good hat" is essential to protect your walls and foundation,why put it on last?

Considering all the houses built by MANY of the folks using super adobe have the roofs placed on TOP of the hyper adobe, I'd say yes, it's load bearing.  But that also depends on HOW YOU BUILD IT.

I'm sure not ALL adobe is load bearing, and there is no way to know for a yet un-named, un-engineered project.  Kind of like asking "how much will it cost" when one doesn't know the size, scope, or finishes desired for a house.

Why put it on last?  That was thoroughly explained.

If you try building from the top down, (as opposed to the bottom up), the roof will be in your way, have  to be supported by something other than the walls themselves, and there is no benefit I can see to building the roof first, and in fact, could create problems later.  It's always easier to adjust a roof if the building isn't perfect than to try to adjust the walls to meet a roof.  

When you're dealing with conventional construction, everything is standardized.  Your lumber, plywood, etc, are all build and manufactured to a standard.  No matter who you get a 2 x 4 from, it will be 1.5" x 3.5"    With super adobe, and sandbag building, theres a lot more variance.  Some wall sections might be a tad thicker, some a tad thinner.  That will affect placement of a roof.

William Bronson wrote:
If a "good hat" is essential to protect your walls and foundation,why put it on last?

Lets use your hat example, and I'll ask this question:

Would you put on a hate before putting on your undershirt?  Or your dress shirt?  

How about putting your pants on BEFORE you put your underwear on?

Try putting your shoes on, then your socks afterwards.

THAT's why you put the roof on last.  

Greetings all,
Thank you for your responses. You gave me a good giggle, as well as pause for thought (Eddie Conna) and I appreciate your advice. Thank you William Bronson for following my thought process!
I realise it's a bit odd to put your hat on before your underclothes...., but sometimes I do match my outfit to my hat!

I should explain...I'm going to be building in my spare time, a long way from where I live currently.
I thought that if I have to leave the build unfinished for any length of time, which is likely, then at least it would be protected. I'm building in the mountains of Portugal, where it is likely to rain a lot for at least part of the build.
The roof I'm planning will have at least a 4 foot overhang all round the oval building, to keep the house cool in the heat of the summer, but will also allow the lower winter sun to warm the house through the South facing windows.  The plot faces South.

The first job will be to construct a gravel foundation trench (Owen Geiger- earthbag building) along with a solid gravel foundation for the footprint of the house, then complete the first stages of a rammed earth floor.(Sukita Reay)
Then I'd like to do a timber framed roof with roundwood supports regularly spaced at a distance of 4 foot from the edge of the wall footprint. This way I can tarp the frame and carry on working come rain or shine. From what I gather, Earthbag laying and earth plastering are best protected from rainfall, until it has hardened and been lime washed.

Earthbag walls are super competent at bearing loads...not worried about that at all. They have been known to withstand high impact car collisions and even gunfire.They are one of the safest buildings to use in Earthquake zones. (See Owen Geiger's work in Nepal)
They are also one of the easiest builds for a newbie like me. Local builders will assist me with the roof framing...but I feel confident in doing the rest myself, thanks to many generous people sharing a wealth of knowledge online. All friends and family will be roped in to help!

I'll attend as many workshops as I can though, sadly, not much earthbag building going on in the UK. I love the way these houses look and feel.
I figure I can build up the Hyperadobe walls to as near as damn the underside of the roof frame. I can see that the roof may get in the way at the final stages...but I plan to minimise that by not finishing the edges of the roof until the walls are complete.

hmmm....I'm going to make a scale model .. I'll build a small wood frame first, attach it to a base, and then build mini earthbag walls with rolls of clay. Will post a pic when I'm done.
Please feel free to comment further.

Thanks again

Hi Cath,

Now I understand why you want to do the roof first.  My suggestion would be to build the normal way, (ground up) and cover whatever you've done with plastic before you leave for awhile so it won't get wet.

Also, start with a small main building, complete it, then add to it later as time and funds allow.  That tends to work out better than trying to build the entire thing all at once.

Also, look at the Calearth.org buildings... they are ENTIRELY made of eartjhbag.  No roof... its also earthbag.  The round structures are super strong... stronger than anything else.  That might be a way to go.

Good luck on your build.  

Thanks Eddie...really looking forward to it.

The Calearth buildings are super lovely, but the domed structure's not for me.
Like the idea about starting small. Going to build a small hyperadobe office room in my sister's garden first to get my head around the process.

Good luck with your move to Idaho!

Hello Cath,

Just a few observations and comments ... I am by no means an expert in earthbag building ... or anything else for that matter.  I think the suggestion to start small and add on as needed is great. In your original post, there were a few things mentioned that I have questions about. You said the house would be a 60-70 foot oval and you also mentioned a reciprocal roof (possibly) with maybe 4 foot eaves. If I'm not mistaken, a reciprocal roof must be round. This is not necessarily a problem on an oval building, but with the dimensions you gave, the roof would span 78 feet from eave to eave ... that is an enormous roof even if it were built with trusses. To make it a reciprocal roof would certainly require special construction equipment ... such as a crane. Each individual rafter would be at least 50 feet long and probably 20-24" in diameter. A roof this size is going to put tremendous pressure on the walls.

Starting small also has the advantage of making it easy to build the roof first, on temporary support posts, then the walls. If it's small enough, the roof can then be lower in place, rather then trying to build the walls up to match the roof.

Good luck with your plans.

Peace.

-Thomas

hau Cath,  Tom brings up some good points from the design/engineering side of building.

You can build a reciprocal roof as an oval but you will want to build this as a model first, that way you can locate issues and figure out how to correct those prior to going full size.
This type of roof will have a center section that is built different from the two ends. I would start thinking of two half circle sections for the ends then more standard roof construction for the center section.

The medium you choose will greatly influence whether or not you can construct the timber frame and roof first.
If you are building with straw bales, yes that is how to build.
If you are using earth bags, it will hinder progress to have the entire roof already in place. As you go up, the work space will shrink and earth bags are not light weight like straw bales, plus you have to put in two strands of barbed wire for each course of bags.
If you are using Adobe/ super adobe, these are usually "bricks" and again the work space will shrink as you approach the already built roof.
If you are using Cob, it will end up harder to work the cobs together at the top, but this is indeed one way old cob houses were built in Ireland and Scotland, so it will work.

Model building is a great way to try any approach you come up with. It will show you problems before you get into the actual build. It also allows you try out design features, spacing, materials sizes, etc.
Almost all Architects use models before any building project is started. In the case of timber frames, it even allows you to try different dimensional timbers which could help reduce costs or even better, prevent a catastrophic failure that might end with a human death.

Redhawk

Greetings Thomas and Redhawk,

- "start small" Got it.
I found these plans for a reciprocal oval roof
Pretty much how you describe it Redhawk.

Will definitely make a model, and I found an earth building/timber framing/cob course starting in March not too far from home.
Will also do a small earth bag house based on Owen Geigers designs: https://earthbagplans.wordpress.com/page/2/ in sisters garden.

I've ordered Owen Geiger's instruction DVD on step by step earth bag design. He makes sense to me.
I'm definitely determined to do a hyper adobe house.....check this video on YouTube. Genius.



Thanks again for the advice and encouragement

Just started building a 12 foot Hyperadobe roundhouse in my sister's back garden.  It's been back breaking work, but also very exciting. Will post pictures soon.

Earth bag studio (UK) nearly done!

Waiting for spring to complete the roof and plastering.

Looking good Cath. Can't wait to see more pics of it finished.

Redhawk

Thanks Redhawk. Will post more pics in the Spring.