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Author Topic:   Need your input on an idea
posted 12-01-2002 07:41 AM     Click Here to See the Profile for Barcelona   Click Here to Email Barcelona     Edit/Delete Message
Greetings all;

Came upon an interesting construction method the other day, which gave me a building idea. I thought I would put it forth here, and see if y’all could give me any reasons to reject it.

By way of background:
As I was wandering through downtown Anchorage, (Alaska, USA) the other day, I happened upon a crew building a wood framed, plywood sheathed building. As this is earthquake country, (had a 7.5 or so about 3 weeks ago), this is a wise way to build buildings with flex to withstand the shaking (but I digress). Anyway, it seems that the builder wanted a more masonry look to the exterior of the building. The carpenters were applying a Styrofoam exterior paneling over the plywood, then carving stone shapes in the face of it. Over this the plasterers applied a stucco finish.

Now, on the parcel where Helen and I are trying to build our castle, we have lots of stone, about 80 Acres of it, (mostly granite), lying about a foot below about 80 acres of 60-75 foot (20-25 m) Birch and Spruce trees. The subsoil is a “well graded sand and gravel glacial moraine“, ranging in size from windblown silt, to sand, gravel, rocks, boulders, all the way up to “screw this, go get the bulldozer“. It drains well, dampens the earthquake movements, and will make great rubble to infill the walls. The only problem is, its rounded, and therefore pretty much worthless as a facing stone.

I have been considering using slip-form style concrete with a bunch of really big aggregate to make the walls of our first tower, even though that would leave us with that wonderful poured concrete facade. However, after a little research on the web, I came up with Insulated Concrete Forms (ICF), which is concrete forms made of two 2 in (5 cm) Styrofoam panels, linked with plastic ties of various lengths, for various thickness of walls. The price of the foam panels is pretty much made up for by not having to build the wooden form work. The insulation value of 4 inches of foam is a nice plus, and I think we could do something like a fieldstone surface treatment before putting on the stucco layer. Another possible plus would be waterproofing the exterior surface of the structure to protect against the freeze-thaw cycles of our -30°F (-34°C) winter temperatures.

I’d be interested in what you think. The purest in me cringes at the thought of sheathing the whole thing in plastic foam, but the pragmatist in me wants to try it.

Thanks for your feedback

The hardest part of building a castle is setting the first stone.

Erik Schmidt
Senior Member
posted 12-01-2002 09:34 PM     Click Here to See the Profile for Erik Schmidt   Click Here to Email Erik Schmidt     Edit/Delete Message
Hi Barcelona,
I must say I'm a little confused as to which particular method you wanted comment on.

One thing I think you should decide is what kind of exterior look you want your castle to have.
If you don't mind the rendered look, which was done in the middle ages, then it doesn't really matter what kind of wall construction you use, as it won't be seen.
If you want a stone wall look, then it gets difficult, especially considering the stone which you have and the earthquake problem.

I think using the slip form concrete with boulders may be a cheap option, but may not be the most suitable for an earthquake zone.
Adding a stone shell facade is unlikely to hold up well in an earthquake either, as it is thin, the stones rounded(don't rest well on eachother) and you may encounter shear between it an the main wall during an earthquake.

I have looked at many old stone structures in the earthquake prone middle east (Israel, Turkey, Jordan) and have found that it seems to be the structures built from closely fitted stones which survive best.
One thing to note though, is that modern concrete and mortar based on portland cement was not used then. They used lime mortars and concretes which have quite different properties to the modern replacement. Concrete is chemically unriendly to stone, it is very stiff and does not conduct water well. The old lime based materials are porous, allowing free drainage of water, and in fact somewhat soft, allowing for some movement of the stones, making a wall less prone to crumbling during an earthquake.

Given your weather conditions, you will want insulation within your wall, so the foam is probably a good idea.

I hope that helps a little.


posted 12-02-2002 04:59 AM     Click Here to See the Profile for Barcelona   Click Here to Email Barcelona     Edit/Delete Message
Thanks Erik;

I must apologize for the scattered nature of my original post. I know better than try to make sense this time of the night/morning.

The intended question was about the use of the Insulated Concrete Forms. The desired appearance of the tower would be that of quarried stone. The lines of where the blocks meet would be incised in the surface of the foam for the texture, and the entire surface would then be covered with a layer of stucco.

A few additional questions, if you don’t mind.

Could you please give me a bit more detail as to what is entailed in “the rendered look”? It sounds interesting.

I also need just a bit more clarification on, “Concrete is chemically un(f)riendly to stone, it is very stiff and does not conduct water well”. I understand that Portland cement is much more adhesive, more rigid and less porous than earlier cementing agents. Is the water that you wish to conduct the condensation from the interior living space, or from some other source?

I appreciate your time, and your patience. Thank you.


Erik Schmidt
Senior Member
posted 12-02-2002 05:58 AM     Click Here to See the Profile for Erik Schmidt   Click Here to Email Erik Schmidt     Edit/Delete Message
It was usual to render the internal walls of most stone, rammed earth or tapia buildings, and in some cases, the outer walls were also rendered.
This simply means that a layer of mortar-like material was added to the surface, thereby obscuring the surface texture of the construction material underneath.
So, my reference to the 'rendered look' is simply that the surface is faced with render and does not show the underlying material which makes up the wall. That would allow you to build the wall of almost any material you like, and simply pretend that there is a medieval stone construction underlying the smoothe outer surface.

You may not know what 'tapia' is, which I referred to above. It is similar to a modern concrete mix, but using the lime instead of portland cement. The romans were masters at using it, and it was often used by the Moors in Sapin in building their fortifications.
It is poured into formwork, like today, and appears externally like a solid mass except for regularly spaced holes from the formwork as well as a slight striated look, from where each new layer was poured on the one below in about 40-90cm rises.

As for the foam concrete forms I really can't say either way. I have heard of them, but don't know how well that would stand up to wear and tear. I think that the foam surface needs to be covered in a thick layer of render to help protect it, but the sales rep would be better placed to tell you about such things.

If it is indeed possible to make the stone outlines in the foam and add stucco, then it should look fine. Just be sure to study the real thing to insure you make the outlines for the stones in a realistic way. I have seen quite a few churches with fake stonework painted on the plaster covering the internal faces of the real stonework. No idea why?

Portland cement can chemically degrade cetain types of stone, especially sandstone as far as I recall.
The fact that it is less porous means that it can force the stone(if it is porous) to absorb water, which can speed up degradation, especially in frost prone climates. I don't think that would be a problem with granite though.
As for the water, the source is irrelevant. Whether it's condensation from inside or rain from outside, you don't want it hanging around in your wall.

I wish I could be of more help, but I speak from what I have read and seen, not from practical experience.Erik

Senior Member
posted 12-02-2002 08:20 AM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
Is your granite the decomposed type, meaning crumbly, or is it a solid mass? It does make a difference in the mix of the mortar and the infill equations.

A roughly rounded stone for infilling a wall is fine from a historical and modern standpoint in or out of a earth quake prone area and can actually make a wall stronger by the use of soft ball or larger stones.

Although lime stone is the best for binding lime or portland many other types have and will continue to be used.

It's the binding agent and its mix and how much is used between the stones that can help to make or break a wall.

The size of the stone, apox weight of the typical piece and composition is important to figure the sand/lime or portland ratios.

What is yours like, how big or small were you going to use for infill?

Some where in BYOC is several discussions on the slip form and the use of Styrofoam panels, both systems go up fast and are a bit cheaper to use then some other methods.

Reject this method? No Way!
IS it right for your needs and budget?
Can the product be gotten at a reasonable price in your area with out large shipping charges?
IS it something you feel comfortable using?
IF it is, then go for it!!!!!

Speaking of outer facades.
One other thing is pre made "stone". Around here its known as "gem stone", its not too bad expensive and is custom ordered for size, shape, and color.
It glues into place over any smooth surface and I've seen it made to resemble Ashlar limestone.
Just an idea or two.

Erik Schmidt
Senior Member
posted 12-02-2002 07:26 PM     Click Here to See the Profile for Erik Schmidt   Click Here to Email Erik Schmidt     Edit/Delete Message
You tweaked my memory there Duncan.
In Israel, and especially in Jerusalem, due to mandation by the building code, allmost all new buildings and walls are faced with local stone.
The structures are built from poured concrete which has regular rows if wire embedded so that it sticks out on the surface.
This wire is used to help hold the motar mix which is used to bind 3-4cm thick sandstone facing onto the wall. I think the wire is set out so that it aligns with the joins in the stonework. The stone is rough faced and cut into about 40cm by 25cm 'tiles' which, when fully finished look like a solid stone wall built of squared sandstone.


posted 12-02-2002 09:57 PM     Click Here to See the Profile for Barcelona   Click Here to Email Barcelona     Edit/Delete Message
They use a similar technique up here. When laying up concrete block walls, they insert metal tabs at intervals between the courses. These are then used to anchor a facing layer of fist sized stones of the local rounded variety and the cement based mortar which lends the appearance of the wall being made of those stones. I hadn’t really considered it, since I hadn’t planned on building with concrete block, but maybe I should give it some thought.

Duncan, in answer to your question as to whether or not the granite is decomposed, this stuff doesn’t even consider itself middle aged yet. I took a fair number of samples, and tried smacking them with a 2 pound hammer, to see if they had any natural cleave lines, and merely left white marks on the surface. when I tried it again with a 2 handed, 8 pound sledge the result was not much greater. I figure the glaciers acted as a great sorting machine, turning anything softer into silt.

As to the size of the local stone, it is a mix of all sizes. all I have to do is build something to sort out the size or sizes I want. I once made the mistake of having the teenage kids collect softball sized stones off the surface for a project I was doing. Now they refuse to come back out, for fear I will do it again.


Erik Schmidt
Senior Member
posted 12-03-2002 07:52 PM     Click Here to See the Profile for Erik Schmidt   Click Here to Email Erik Schmidt     Edit/Delete Message
In regard to the metal tabs, why don't you use that technique in conjuction with the foam forms. You don't need to use concrete blocks. In Israel it's done with poured concrete.
You could modify the technique to the foam form walls. It may be as simple as pushing the wires or tabs through the foam so that they become anchored into the poured concrete on the inside and stick out to hold the shell on the outside.


posted 12-05-2002 04:00 AM     Click Here to See the Profile for Barcelona   Click Here to Email Barcelona     Edit/Delete Message
Is my face red?!

Of course ! You don’t even have to push them through the Styrofoam. The panels are about 16 to 24 inches high, so the tabs could just be laid between them so the end is inside the form, and the other end is sticking out. As an additional method of securing the face, You could hang hardware cloth from the tabs, to give the concrete more steel to hang on to.

This would serve to give the first tower a rough cobbled surface, which would look older and more primitive, which is just what we want. We’ve been planning to try to use a number of styles of architecture of increasing sophistication to give the impression of a castle built over a fairly long span.

I can only wonder how long it would have taken me to figure that out. :-) Thanks.


Senior Member
posted 12-05-2002 06:42 PM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
Sorry for being a bit tardy, I've had some construction work to consolidate before the winter sets in.

In my opinion your stone will increase the strength of the inner walls greatly and it would be hard to find much better. Your lucky to have it so ready to use.

As a thought, I think those Styrofoam panels have extra long anchors or can be ordered with them.

Senior Member
posted 12-06-2002 03:25 PM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
I re-visited your web site and found it very interesting. Many things are different then when i first visited.
You probably have had your fill of people saying what about using this or doing it this way, but i'm going to add to that list in answer to this excerpt taking from your project page.

"The water system for the tower will consist of storage tanks built into the floor of the 4th floor with water being brought in by truck and pumped up into the tanks, at least until a well is drilled"

I believe you have a high rain fall amount, why not use a roof drain that feeds into a cistern as many castles did.
Some used multiple drains from the battlements to collect as much water as possible.
Some "tanks" were placed on floors below the roofs or were built into a wall.
I know of one that was in a Scottish Tower House that was 22 inch's wide at the top and gradually widened at the base to about 8 feet long and 6 feet wide 4 storeys below, not a great deal of water but more then most would think.
Many castles may have had several tanks in the walls.
As for contaminants, a screen over the fill area possible next or close to a valve and a water pre-purification system before it ever gets to the tank. This might be as simple as a 55 or 30 gal. drum with sand/lime/charcoal or other mediums.
Below near the tank might be the larger and more complex purification units.
This might keep down the cost some even if used only for gray water.
Just an idea or two.

Megan and Ralph
Castle Duncan

The Web Site and Castle Duncan Forums

[This message has been edited by duncan (edited 12-06-2002).]

posted 12-07-2002 02:51 AM     Click Here to See the Profile for Barcelona   Click Here to Email Barcelona     Edit/Delete Message
Not a problem, Duncan. The purpose of life is to learn, and to close your ears is to begin to die. Feel free to offer any suggestions you have.

Helen said she had been working on the website, guess I better go take another look at it myself.

When we were first talking about our water supply, we had considered rainwater but without doing any calculations, it seemed like the surface of the roof was rather small, and would return an inconsequential amount for the work involved. After you mentioned it again, I did some, using 20 inches annual precipitation, and 490 sq. ft. of collecting surface, and came up with a possible 6000 gal/year (a mere 24 tons choke). Certainly an amount worth conserving. Now all I need to do is the design the tankage and structure to hold it up.

One of the things I need to work on would be how to keep the feed pipes from freezing in the winter. For the most part, people up here don’t use gutters and drain spouts, because the freeze in the wintertime, and either rip off, or burst. The few that use them have to either take them down in the fall, or run heating wires through them, and heat them electrically all winter (feels like 5 or 6 months).

What I was considering was to slope the roof beyond the walls to have most of the runoff recharge the local aquifer. The subsoil is mostly sand and gravel mix under the topsoil, and should drain quickly, and act as a filter. Then we could use a rather shallow well to draw the stored water for use, already filtered by its passage through the soil. We plan to eventually use a small period style windmill to pump water to tanks in one or more of the final towers to provide water pressure. Something smaller than the 6000 gallon size, I should hope.


Senior Member
posted 12-10-2002 08:34 AM     Click Here to See the Profile for duncan   Click Here to Email duncan     Edit/Delete Message
I can see how your plans would work out quite will.
In thinking about the roof drain, I wonder if some where in Scotland's many Castles there might be a fix for the overhang freeze problems.

posted 12-10-2002 09:01 AM     Click Here to See the Profile for THE TIKI     Edit/Delete Message
Hello Barcelona, I've been reading your posting and the replies fairly frequently as of late. I'm intrested in your construction costs and raw material amounts, you see I myself have a project of my own,I have to turn a report into my proffesser about castles, and while I've completed the body of the paper, A table is required to even be accepted! The amounts of stone, lumber, mortar and man hours seem to be the best things to form into a table. But I can't seem to get any estimates from anywhere! I was wondering, as you're building a castle yourself, if you'd let me know How much of each material you need? I'd really appreciate your information. Thanx -Tik

[This message has been edited by THE TIKI (edited 12-10-2002).]

posted 12-10-2002 01:47 PM     Click Here to See the Profile for Barcelona   Click Here to Email Barcelona     Edit/Delete Message
Tiki, nothing would give me greater pleasure than to be able to give you some solid figures on the cost of castle building, as that would mean I had SOMETHING built. At this point, all I could give you would be costs of land clearing, and estimates for anything else. Estimates, I have found, are just the bait that a project uses to suck you in.

For example, We had been planning to use straw bale construction to build some or all or the interior buildings. The cost estimates looked favorable compared to conventional methods, and there would be the added bonus of R 50-60 insulation (always a plus in Alaska). As we got further into the project, however, we discovered that the cost estimates we were using were based on California grown straw bales. Because of their vastly greater straw production (a by product of grain production), and their stricter air pollution standards, the cost of straw bails was substantially lower than ours. Since burning of the straw in the field in preparation for planting the next crop is restricted, the builders were able to get their bails at no cost in some cases. A similar bail grown in or imported into Alaska was for sale for $6.00 each. We were not prepared to start growing our own oats, just to harvest the straw.

But enough of my whining. Perhaps some of the folks who have more to show for their work might be able to help you.


The hardest part of building a castle is setting the first stone.

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