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within limits drawn around us by the equal rights of others. ~ Thomas Jefferson
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Friday, February 14, 2014
Construction Guy Needed
Construction guys: In the old days a tower such as above was probably built on a foundation that was dug and filled with a rule of thumb guesstimation. I'd imagine a hole was built and large stones chucked in to ground level, then building would begin, including mortar.
I may be dead wrong.
But given the probable age of this tower and its lack of tilting, cracking, falling down - it seems to have worked.
So, if a guy wanted to build a few such towers or similar fortifications using rule of thumb, how would he go about it? No pored concrete (or very little). No rebar (or very little).
Second Issue: If a rule of thumb guy wanted to dig a functional trench covered with a light coating of soil, what would the rule of thumb engineer suggest he do?
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Personally, I wouldn't bother. Fixed structures have been a waste of time since cannon came into widespread use. They only act as a beacon for the enemy and, once inside them, it is difficult to get out.ReplyDelete
Far better to have a series of well-hidden refuges from which you can sally. And by well-hidden, I mean ones that are not obvious, not just out in the country. Hide in full view!
Anon: I agree and disagree. In the coming Liberty Games fortified positions are toast against .mil - that is a fact. But I don't think .mil is going to be in a position to task many resources as they wish.Delete
Indeed, in a local setting, fortified locations give the populace a rally-point, something to defend. And if we have done our jobs and given the local populace reason to stand and defend with us, such fortifications have significant strategic and tactical value.
On top of all that - the premise that fixed fortifications have been obsolete since cannon - well, can you identify a current US .mil facility without a fortified, on some level, perimeter and infrastructure? ;)
"But I don't think .mil is going to be in a position to task many resources as they wish."Delete
If they don't target you, then it was a waste of time. If they do target you, then it was a waste of time.
Cost/benefit analysis. A well-fortified position is overkill against local gangbangers, useless against multiple Hellfires, let alone tactical nukes. OTOH underground positions aren't useless for either.
"And if we have done our jobs and given the local populace reason to stand and defend with us, such fortifications have significant strategic and tactical value."
Fair enough; that's a good pragmatic appeal. Me, I'd rather hope that their own lives would fulfill that particular purpose. But that's me and I admit it's only a hope at this point.
BTW US military facilities aren't fortified because they're worried about an attack from the US military. You know from whom they're worried about an attack.Delete
A King's castle doesn't do much against a full invading army, but it does a swell job of keeping the peasants out.
Rebar and concrete would be the modern option. And a much more workable foundation. However, if you are dead set on doing it in a fashion to how it would of been done say during medieval times. They are building Guedelon Castle in France using only techniques and materials available to them during the appropriate time frame. I can do a bit of research and let you know what they used if you are dead set in doing it in such a manner. As far as a trench goes. Use a material that is strong enough to hold the weight of the soil, and any potential snow, small animals, etc. I would be concerned about larger animals falling in though. Also want a material that will not deteriorate due to climatic conditions. Corrugated plastic comes to mind.ReplyDelete
Thanks, Kevin. I'm not wedded at all to the old ways - I want it to work. Concrete and rebar it is. ;)Delete
There are a lot of options if you are not wedded to traditional masonry. It is possible to use a combination of stone, concrete and rebar, with reusable small forms, to 'jump form' masonry structures. Mortared stone on one or both sides, with rebar and concrete in the middle. Does not require the same time as traditional stone work, much stronger and more ductile than solid stone, and cheaper than Cast in Place concrete. You can use a small concrete mixer to provide the mortar and concrete so it is easier to build in remote sites (you don't have build a good road for a ready mix truck.)Delete
ANother point- footings not only have to be below the frost line, but they have to bear on adequate strata, strong enough to carry the load with minimal settling, which is especially bad for stone masonry. One must also be wary of the potential effects of clay soils, some of which can be highly expansive.
I am not an engineer or an expert in masonry so the following is my opinion of what I think it would take to build a stone tower based on my experience in construction industry. If anyone has further information or corrections, please comment.
Foundation: Requirements depend on size of tower. Without a basement, it appears the foundation need only be 24” – 30” deep to stay below frost line. Frost line depth varies by geographical location. If the existing soil has good bearing capacity, then you can probably get away with building the walls on virgin soil. A layer of stone aggregate, possibly sand may be used to level off the grade. The castle wall would start on the bed of stone and continue up. There would be no independent foundation wall.
Walls: The type of stone has a significant impact on the strength of the wall - the larger the stone, the stronger the wall. The mortar is the weakest length so the less mortar required, the better. Stone is not cheap, the best information I can find indicates that basic material will cost around $250 - $350/ton or roughly $375 - $525/cuyd. There would likely be a significant delivery charge on top of this. Of course, the larger the stone, the heavier the equipment needed to lift it. I would think that any reasonably skilled bricklayer/mason could set the stone. If multiple stories, pockets would be required for timber floor joists.
Floor: Floor could be a typical concrete slab, or mortared flat stone. Floor should be set several inches above exterior ground.
The higher the tower, the thicker the wall will need to be and larger stone will be required. Most castles with larger walls were built with quarried stone that was cut to specific dimensions. The smaller tower in the picture appears to have been built with something similar to a field/flag stone which is ok for this kind of tower since it is not very tall and appears to serve only as a guard station. Weathering is dependent on climate and level of quality. The tower in photo appears to be in a warmer climate so is less susceptible to freeze/thaw deterioration.
Another significant challenge will be building codes. The “officials” won’t take kindly to structures not engineered by licensed professionals. Zoning may be another issue.
There is a company in northern Idaho that builds castles, they are about an hour from Coeur D’Alene.
Castle Magic in Sandpoint, Idaho http://www.castlemagic.com/
For a structure to last, not tilt, settle, crack, it needs a solid foundation that goes below the frost level, so that the freezing and thawing of the ground doesn't move the foundation, no matter what it is made of.ReplyDelete
I have seen concrete/with rebar crack, break because it froze below the lowest level of the foundation, causing it to heave and move . And I've seen structures on stone on stone that were deep never moved.
foundations make the building last
Thanks, Gary. And thank you for the recent pictures! Holly and I went through them several times.Delete
I have to do some studying on ratios - above-ground structure versus required underground required sub-structure/footings.
A lot more to it than just chucking stones into a hole, and the Romans, at least, understood pozzolanic cement, and used it to mortar foundations together. Often, and especially when using large quarried stones, each stone was carefully carved, set into place, and then joined to its neighbors with 'cramps' essentially a big hand-forged wrought iron staple. The stone mason would drill two holes, one in each adjacent stone, and also chisel out a trench for the horizontal bar of the cramp. Once the cramp was in place, the space between it and the stone was filled in, sometimes with lead, sometimes with liquid sulfur, and sometimes with pozzolan.ReplyDelete
Footings were typically made of quarried dimension stone, laid across the width of the trench, perpendicular to the axis of the wall, and each stone was very carefully bedded in well-graded gravel. each successive layer would reduce the width of the footing; typically a 1 to 1 slope was maintained, until the wall width was reached.
Thanks, Historian - points all taken.Delete
2' is the typical rule of thumb when it comes to footers or walls that are not "buried" but fully exposed. My ranch house does not have a footer. LOL, yeah wrap your heads around that folks. The barns in my area share the same footprint as my basement. They set on crushed stone. If the wall is exposed, the crushed limestone was put down in 6" lifts and tamped until a depth of 2' is acheived. The other walls that would be covered with grade were about a foot. The footprint was 2' wide and my precast basement for a 27 1/2' x 54 ranch home was up in 3.5 hours. Email or text me if you need any more regarding this. My father and I did a majority of the construction at my house.ReplyDelete
I bought a book on foundation engineering and another on soil geology from the local used book store for about $15 total. Lot of interesting reading in there. Like another poster said, foundation needs to be below the frost line. Footers are dependent on the weight of your structure and also the soil composition. Different soils determine different width footers for the same structure.ReplyDelete
Good luck with your building, I'm on my way to becoming an amateur stone mason myself :)
If you can, get a Geotech firm to determine soil bearing pressure. If not, uncompacted good quality native material can support approx. 2000/2500 PSF. If you compact base rock to 95% you can get to about 4000 PSF. Dig down below the frostline and calculate the weight of your planned structure. Concrete or rock weighs 150 lbs/ cubic foot, or 4050 lbs per CY. Use the weight to calculate your needed footprint, and make sure you distribute the load evenly. For underground, if you just want concealment, and assuming the walls are stable, use pressure treated 4x4 and treated plywood for up to about 4' wide trench. Dirt weighs about 120 PCF. To avoid the "hollow" sound go about 1 foot down for every foot wide from the surface to the top of your trench cover.ReplyDelete