Cement, Lime, And Sand

Welcome to my nightmare, a French village house.  Many American and Brits, as well, believe that the French country houses are stand alone affairs, just like in dear old America or the UK.  Well, out here is god’s country, or at least the farm land of France, about the same difference except most of the churches are closed due to almost no congregations.  Religion in France hasn’t been that important since the revolution when the poor and destitute decided that the church was too rich.  The church didn’t help itself much either during that time and since has been in a state of long decline.  Let’s face it, ever since De Gaul the French have become ungodly, especially on Sundays.  But all that aside, let’s get back to houses and the differences we find in France.  Village houses are common wall affairs where only the end units have walls with three sides unless they stuck a barn on that side.  The houses are usually made out of stone the old fashion French way.  The Romans show them the correct procedure for building stone wall structures but the French said buzz off or what ever is the correct way of saying buzz off in French.  I’m sure I’ve heard the expression somewhere, but I don’t speak French, bad hearing and all that.

The classic Roman stone wall is two courses of stone, an inside and an outside wall with cross members every meter in height.  They also used a cement foundation rather than place the stone directly on the ground.  What this method does is provide an inner space of captive or dead air as an insulation against the cold and heat.  While not exactly a vacuum, it works remarkably well in extremes.  Now this method will work even if the stone is a bit irregular.  That is why s0o many old Roman buildings have remained intact over the centuries.  But the Gauls and the other wild tribes that would include the Brits (your wild tribes, you) changed the instructions on wall building.  I would believe that the main reason was siege warfare.  That is, you make the outer wall of the hardest stone, like granite, and perhaps let the inside be limestone or sandstone because of its softness in comparison.  But quarrying stone is hard work, takes time, and is labor intensive and expensive.  Imagine then if one want a wall ten feet thick and fifty feet high how much stone one would need to quarry to build a hundred yard by hundred yard, excuse me, make that meters, the idiots proclaiming the virtues of metric measurements over the King’s standard.  One way to build it cheaper and quicker is to use fill.  That’s right.  dirt and churt, and small stones from the quarries and even some mortar.  Hence the title, mortar is one part cement, one part line, and four to five parts sand.  Use more than five parts sand and the mortar will degenerate very early.  Use less sand and the mortar will be harder.

So why should it matter about the sand content of mortar?  Why not use cement?  Well, normally most cement mixes use some proportion of gravel.  Reason being that the cement needs hard stuff to cling to.  Of course cement is a combination of gypsum, lime, and calcium in varying proportions.  When these molecules are mixed with water the result is a hard substance.  But cement is very brittle.  Build a brick wall with cement and it doesn’t take too long before the surface of the bricks start to pull away from the cement.  So if one adds more lime the mortar becomes a bit more plastic and tends to stick to the stone or brick.  The caveat being that the amount of mortar used between the brick or stone can’t be too wide.  One usually does not like more than a quarter inch between surfaces that are being joined with mortar.  But back to our building methods.

The reason why so many old castles are damp is that there was no foundation.  That means the rock or stone was placed directly in the ground, two courses, an inside and an outside course.  And then fill was place between them.  All that dirt, churt, smally rock, pebbles, and so forth, and what do you end up with?  A nice wick that sucks moisture out of the ground and up inbetween the walls.  Of course the French have never learned.  Pour concrete directly on the ground for a floor and the concrete is porous enough to allow water to migrate through and mold to grow on the floors.  The only way to stop the mold is to put down tile.  So it goes, walls and ground floors are problem areas that never quite get solved.  Of course the use or mortar with lime in it means that erosion will effect it over time and it must be replaced.  This is where you learn just how lazy and cheap the French were back in the fifteenth and sixteenth and seventeenth centuries.  You have walls that are about twenty inches thick and where they had used mortar, some of that has pretty much been, over time, reduced to sand as the lime, gypsum, and calcium have been leached out, particularly in the interior of the wall where all that moisture acts as a chemical agent.

So every twenty years or so the outside walls need to be repointed.  That is, the old soft mortar is scraped or chiseled away to a dept of about two inches, maybe less, and new mortar placed in the channels.  An inside wall may need this once every fifty years or so.  When the walls are neglected and the proper maintenance not done, the walls are subject to hydraulic collapse (water is sucked up in the fill and freezes in severe winter, causing the first expansion, then the ice melts and causes the second expansion.  Simple wind and rain erosion will also cause stone fall out of its place and compromise the wall.  Often times the clay tiles leak and rain water seeks into the middle fill.  Stone houses don’t last forever, they take a bit of maintenance.  So I am working on an inside wall in my setting room.  The French fools did tow things wrong.  The first they slathered mortar over the stone, trying to render the surface.  Think of it as stucco.  But that only works if one repoints the walls, adds new mortar, and then puts that protective coat (the rendering) over the stone and mortar.  The second mistake is that they used regular cement to fix some of the cracks but they did not take it far enough.  They left cavities in the wall that should have been filled with cement with small pebbles added.  the cement works better if it has something to grab ahold of and stick. an increased surface.  Pebbles provide that large surface.  Well, just another wall to fix.  I have repaired quite a few both inside and out.  It’s a lot of hard work but when done right it protects my investment.

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