working with a large boulder to create a tiny cabin / shelter

Hello good evening everyone, we have a small property in the chaparral desert and we wanted to start building a tiny, low-budget cabin where we can camp out while we start working on more permanent features such as a fence, swales, fruit trees and a more permanent house with natural building methods. Now initially, we had thought about building a small, wooden A-frame cabin BUT I just remembered that temperatures here in summer get to around 35 to 40 degrees C (95-104 F) and that would totally cook us alive. I honestly don't have much money and am trying to go as low budget as possible since I also have to spend a lot of our money on fencing and fence posts to keep out cows, horses and other unwanted guests. Now, we noticed a possible permaculture-ish solution to our dilemma on the property, we have a few large boulders and this one has a flat but curved top, I think it's granite. Our idea to solve the issue with the excessive heat, is to build a tiny cabin right next to the boulder (towards the west) and even use the surface of the boulder as a wall if possible. The angle the camera is facing is towards the west, so the boulder should cover us from the morning and mid afternoon heat at the very least and act as thermal mass throughout the rest of the day. My grand question now is: how difficult would it be to work with that large granite boulder to take advantage of its natural properties? should I build some kind of earthbag / cob structure attached to it, or something like an earthship structure? what would I need to do to level off the top, can you drill into the rock, pour a little cement on top and make it stick in order to eventually place a large cistern on top? I apologize, I know there are probably like a million different factors to consider but I wanted to get some input from people with more experience in this. Thanks!

Wow, that's some impressive thermal mass.  Could you build off the North side instead?  Then you'd be in its shade as well.  One challenge would be keeping rain (if you get any) from getting between the rock and your structure's roof.  Unless your roof snuck under the overhang of the rock.  I'm guessing even wood walls would be fine with all that thermal mass to keep you cool.

Mike Haasl wrote:Wow, that's some impressive thermal mass.  Could you build off the North side instead?  Then you'd be in its shade as well.  One challenge would be keeping rain (if you get any) from getting between the rock and your structure's roof.  Unless your roof snuck under the overhang of the rock.  I'm guessing even wood walls would be fine with all that thermal mass to keep you cool.

Thanks! it is a great thermal mass, that's probably why there are native plants around it. We can definitely do North-West to avoid bothering the shrubs.

I totally understand the impulse to use that rock as a wall.  I think its a great idea. If its really granite then you could sink some bolts into it as well and sort of use it as a foundation piece to hold the roof/walls.

A different idea is to actually build the house AROUND the rock.  I know that might be larger than you are presently considering, but it might be worth some thought.  By putting that mass inside the structure you have a huge thermal mass that you can, sort of, control. Alternately, if its used as a wall consider building a simple shade wall/roof to protect the rock from solar heating - anything you can do do keep that rock cool so it can soak up heat from inside your structure will be great.

Mike Autumn wrote:My grand question now is: how difficult would it be to work with that large granite boulder to take advantage of its natural properties? should I build some kind of earthbag / cob structure attached to it, or something like an earthship structure? what would I need to do to level off the top, can you drill into the rock, pour a little cement on top and make it stick in order to eventually place a large cistern on top?

An experienced natural builder has a more valuable opinion than mine ... but ... cob is probably a good idea for joining any structure to the rock.  Its gonna be hard to get any wood to sit against it well.  BUT cob requires clay - not a big deal unless, you know, Baja....  An earthbag seems like a good idea too... there seems to be no shortage of dirt about, and you might find that digging down a bit is helpful for thermal management as well (closer to cooler subsoil, less exposed wall area).

You can absolutely pour concrete on top of a boulder.  You just need to drill some holes to place rebar or similar (bolts?) so that the concrete doesn't depart sideways...  There are also many fancy substances for working with holes in concrete (aka synthetic stone) - epoxies, special cements.  With a hole in the rock you can add a bolt to the rock and then attach something.

Drilling holes may be difficult - it really varies - but know that you need a serious hammer drill to make holes in concrete/ hard rock.  Most are corded.  Might be some ok cordless ones now.

That is a fabulous rock, it may be best to use it as it is.
A cistern on top would be a distraction.
As suggested cob is a good medium to bond to the rock, although it needs more water than rammed earth would use.
Is there any clay in the area?
What will happen with water?.
Plants may be growing next to it because the rock will attract dew and thus moisture which will dribble to the ground.
I suggest it may be a better result to use it as a shelter object and leave the vegetation in place.
I live in a similar environment 45 deg C heat and dry climate.
A small thick walled home designed to exclude heat is something that works for me, with a safari shading roof over the roof and verandas for shade.
Having at least a 3 M ceiling height also helps.
If you plan it well, nothing needs to be pulled down as you extend the structure over time.
I have built a tall tower which draws air through the house, along to lines of middle eastern structures called wind towers.

How does that work in winter anyway? When you want your house warmer then the rock. Do you need to heat the rock or can you insulate it until summer hits.
Maybe in winter you could have a room further away from the rock passively heated on the south side. A room you use less in summer time.. with a veranda that only let’s the sun in when it’s low on the horizon..

John C Daley, I'd like to see pictures of your house.

I remembered reading this when it was first printed (!):
https://www.nytimes.com/2009/11/19/garden/19rock.html

That's a totally different scale of building!  But the quote "Not only has the rock never leaked, it maintains a temperature of 68 degrees throughout the winter" shows you something about mass inside your envelope.

Do this...Petra

This guy is doing a granite integrated cob building in San Diego County; here's the most recent episode(go back into his posting history to watch each step for tips):

I have lived in Chicago, St. Louis  and visited Charleston for a couple weeks. I have traveled extensively through the desert in temps of 100F. and more.

Charleston was the hardest with temps around 90-95F. and humidity over 90%.

Chicago was fairly livable with temps below about 98F. - depending on humidity. Desert travel in temps below about 105F AND in shade was not too much of a problem provided one had enough water - I usually drank more than a gallon a day and did not pee much.

What I'm saying is that for for _light_ activity in dry climate in "hard" shade (shade that does not re-radiate heat onto you) 105F. is not much of a problem. I did not make a habit of heavy labor in those conditions, though.  Depending on your own personal experience and proclivities, you _may_ be good with "105F. in the shade".

The next thought is not about your rock.  (GREAT rock, BYW!)  I have experienced noticeable improvement in hot weather comfort when I can use a double layer of shade.  In desert, my first, second and 3rd thought is SHADE. 1b,2b,3b is convective (moving air) between the primary shade and whatever makes a second ceiling for the personal space.  The thing is, just putting up a sun barrier doesn't get you the huge benefit because the barrier material gets hot and the lower surface of it radiates DOWN and what is "down"  there? You! To realize good shade, the lower surface of that shade needs to remain below about 80F. This is so it doesn't want so much to act like that fancy radiant heating people put into their walls and floors - to keep them warm! When erecting shade, one wants to try to arrange that the side toward you doesn't get too warm and _that_ may mean some kind of natural convective air flow across the bottom of your shade. No matter what makes up your shade.

I have done this semi-successfully with thick light colored canvas tarp over a smaller tent and eating area. The small tent (well ventilated) was actually cooler than the eating area even though it had somewhat less air flow. Inside the small ten there were two layers of shade between me and the sun and (this is the biggee) the small tent material was actually a comfy 85F. while the bottom of the primary shade tarp was easily over 100F. The primary shade tarp was still  passing heat, it was just radiating in the infra-red instead of bright visible spectrum+UV from the sun (which it was protecting us from).

So. When creating shade, keep an eye for ways to help get rid of the heat added to the shade material itself. And plan on a second layer of shade to protect you if the primary layer is going to get hot. I think  the Aussie's have something called a "summer roof" which is a top layer of tin or something that stops the sun which they install about 6" above the weather roof of their homes. The air space is open around edge and helps cool the "summer roof" to reduce it's radiation down onto their weather roof. It also prevents any heat transfer by conduction.

Or, natures way is with a few big trees in the right place to shade your home. Might be worth the years of water angst and sacrifice to see if  you can deep irrigate some big shade trees and get them rooted good enough to survive the real world.

But that rock is truly inspiring. You have found  "Presence" for sure.


Cheers,
Rufus

Here is some info on Wind cooling towers
Windcatcher

A paper on the topic
Science paper

Denise, I have listed details of the wind catchers and I have also created another topic specifically on them.
My tower is about 25 feet tall and draws air through interconnected rooms.
To work better the szie of the opening is a function of the floor area of the area you want involved.
The factor is about 25%. So with large western style large homes, they dont work well. But I design and build
small, comfy homes so its not an issue. My homes average about 900 sq ft with verandas and plenty of outside ares that are not decks[ expensive] or paved areas, [price again]
that peole can readily afford and hopefully use the funds or time saved to muck about with boats, motorcycles etc

Eliot Mason wrote:I totally understand the impulse to use that rock as a wall.  I think its a great idea. If its really granite then you could sink some bolts into it as well and sort of use it as a foundation piece to hold the roof/walls.

A different idea is to actually build the house AROUND the rock.  I know that might be larger than you are presently considering, but it might be worth some thought.  By putting that mass inside the structure you have a huge thermal mass that you can, sort of, control. Alternately, if its used as a wall consider building a simple shade wall/roof to protect the rock from solar heating - anything you can do do keep that rock cool so it can soak up heat from inside your structure will be great.

I really dig the idea (sorry for the pun!) but for now we are building something temporary, if we really enjoy that rock, I think we can move the temporary house aside and build around it instead; thanks for thinking out of the box! (I'm a new dad so I'm getting better at these puns lol)

John C Daley wrote: That is a fabulous rock, it may be best to use it as it is.
A cistern on top would be a distraction.
As suggested cob is a good medium to bond to the rock, although it needs more water than rammed earth would use.
Is there any clay in the area?
What will happen with water?.
Plants may be growing next to it because the rock will attract dew and thus moisture which will dribble to the ground.
I suggest it may be a better result to use it as a shelter object and leave the vegetation in place.
I live in a similar environment 45 deg C heat and dry climate.
A small thick walled home designed to exclude heat is something that works for me, with a safari shading roof over the roof and verandas for shade.
Having at least a 3 M ceiling height also helps.
If you plan it well, nothing needs to be pulled down as you extend the structure over time.
I have built a tall tower which draws air through the house, along to lines of middle eastern structures called wind towers.

Clay it is then! (cob, adobe, etc) We're actually thinking of installing an adobe dome structure and a high ceiling is a great idea! Thanks for the links, I'm trying to consider everything to get a rough idea of what would work best.

Hugo Morvan wrote:How does that work in winter anyway? When you want your house warmer then the rock. Do you need to heat the rock or can you insulate it until summer hits.
Maybe in winter you could have a room further away from the rock passively heated on the south side. A room you use less in summer time.. with a veranda that only let’s the sun in when it’s low on the horizon..

Fortunately, winters are very mild here since we rarely go below 0 C (32 f) on our coldest days but you have a good point, I would need to the rock's temperature in the wintertime.

Dustin Rhodes wrote:This guy is doing a granite integrated cob building in San Diego County; here's the most recent episode(go back into his posting history to watch each step for tips):

I just checked out the video and we're both in the chaparral so it's great to know someone else is already doing something that we envisioned in the same type of biome. I will look at the rest of them, thanks for the video!!

Rufus Laggren wrote:I have lived in Chicago, St. Louis  and visited Charleston for a couple weeks. I have traveled extensively through the desert in temps of 100F. and more.

Charleston was the hardest with temps around 90-95F. and humidity over 90%.

Chicago was fairly livable with temps below about 98F. - depending on humidity. Desert travel in temps below about 105F AND in shade was not too much of a problem provided one had enough water - I usually drank more than a gallon a day and did not pee much.

What I'm saying is that for for _light_ activity in dry climate in "hard" shade (shade that does not re-radiate heat onto you) 105F. is not much of a problem. I did not make a habit of heavy labor in those conditions, though.  Depending on your own personal experience and proclivities, you _may_ be good with "105F. in the shade".

The next thought is not about your rock.  (GREAT rock, BYW!)  I have experienced noticeable improvement in hot weather comfort when I can use a double layer of shade.  In desert, my first, second and 3rd thought is SHADE. 1b,2b,3b is convective (moving air) between the primary shade and whatever makes a second ceiling for the personal space.  The thing is, just putting up a sun barrier doesn't get you the huge benefit because the barrier material gets hot and the lower surface of it radiates DOWN and what is "down"  there? You! To realize good shade, the lower surface of that shade needs to remain below about 80F. This is so it doesn't want so much to act like that fancy radiant heating people put into their walls and floors - to keep them warm! When erecting shade, one wants to try to arrange that the side toward you doesn't get too warm and _that_ may mean some kind of natural convective air flow across the bottom of your shade. No matter what makes up your shade.

I have done this semi-successfully with thick light colored canvas tarp over a smaller tent and eating area. The small tent (well ventilated) was actually cooler than the eating area even though it had somewhat less air flow. Inside the small ten there were two layers of shade between me and the sun and (this is the biggee) the small tent material was actually a comfy 85F. while the bottom of the primary shade tarp was easily over 100F. The primary shade tarp was still  passing heat, it was just radiating in the infra-red instead of bright visible spectrum+UV from the sun (which it was protecting us from).

So. When creating shade, keep an eye for ways to help get rid of the heat added to the shade material itself. And plan on a second layer of shade to protect you if the primary layer is going to get hot. I think  the Aussie's have something called a "summer roof" which is a top layer of tin or something that stops the sun which they install about 6" above the weather roof of their homes. The air space is open around edge and helps cool the "summer roof" to reduce it's radiation down onto their weather roof. It also prevents any heat transfer by conduction.

Or, natures way is with a few big trees in the right place to shade your home. Might be worth the years of water angst and sacrifice to see if  you can deep irrigate some big shade trees and get them rooted good enough to survive the real world.

But that rock is truly inspiring. You have found  "Presence" for sure.


Cheers,
Rufus

I appreciate your considerations on building shade, they'll work great for building a common area and our son's play area since he easily gets tuckered out from being exposed to the hot sun. Good point on the trees, we do have some native shrubs on the North side but placing some quick growing trees on the South end should work wonders then! We already have an acacia tree that is growing fine without any irrigation, well, very little irrigation.

Rock can be shaped - I would consider how that might work in your favour. Can you cut grooves in the rock to direct rainwater away from the structure? Or flatten areas to join walls up with them?

I studied the water situation because you need a lot of it for cob or adobe.
The peninsula of Baja California in northwestern Mexico has few available water resources and is one of the most arid areas in Mexico.
The Tecate River is a sub-basin of the Tijuana River basin, a coastal watershed in Baja California adjacent to the USA-Mexico international border
that discharges into the Pacific Ocean (Figure 1). In 2000, the groundwater resources provided about thirty percent of Tecate’s potable water supply [1],
decreasing to only twenty percent in 2015 [2]. In addition, with the increase in population, urbanization, and industry in Tecate,
there is a concomitant increase in contaminants being introduced into the Tecate River and groundwater resources. The Tecate River,
which under natural conditions is an ephemeral stream, has become a perennial one with poor water quality downstream of the discharges.

I am worried it may be a big issue for you.

John C Daley wrote:I studied the water situation because you need a lot of it for cob or adobe.
The peninsula of Baja California in northwestern Mexico has few available water resources and is one of the most arid areas in Mexico.
The Tecate River is a sub-basin of the Tijuana River basin, a coastal watershed in Baja California adjacent to the USA-Mexico international border
that discharges into the Pacific Ocean (Figure 1). In 2000, the groundwater resources provided about thirty percent of Tecate’s potable water supply [1],
decreasing to only twenty percent in 2015 [2]. In addition, with the increase in population, urbanization, and industry in Tecate,
there is a concomitant increase in contaminants being introduced into the Tecate River and groundwater resources. The Tecate River,
which under natural conditions is an ephemeral stream, has become a perennial one with poor water quality downstream of the discharges.

I am worried it may be a big issue for you.

Thank you for researching and worrying about us! I'm truly grateful for your effort, fortunately we are all the way in the bottom left part of the municipality of tecate, at least a 40 -50 minute drive away from the main city. We have a well here and it's fed by the Las Palmas aquifer, while not as stressed as the sources in the city of Tecate that you mentioned and Ensenada, it still presents a challenge. We are thinking of doing some good earthworks, rainwater collection and planting a lot of native species to retain as much water as possible in the landscape and local aquifers. I'm gona give atmospheric water collection a shot in several experiments such as stone mulch around trees, dew collection on flat panels and a rather interesting method I learned in a scientific article that consists of a transparent glass pyramid that contains a water retaining solid that expels the liquid contained inside after it is heated up. Here's a link to a really good review on sustainable methods for atmospheric water collection. These will be mostly for personal consumption and crop use but the well has provided enough water for a few other cob structures that have already been built.

Review of sustainable methods for atmospheric water harvesting

watewr frim air with a turbine

This is interesting.
It can supply enough water and electricity for a 2000 person village and last for 20 years.
Cost about $US 700,000