Monday, March 3, 2014

Tips On Building A Dry Stack Stone Wall #3: Building The Wall

In this post on building a dry stack stone wall we will look photo by photo 
at the steps in building the wall, specifically aimed at the owner builder.
The photo above gives a look at part of the wall we will be working on.

The complete series are:

The photo above shows the finished wall
 and the section in question is just above the center of the photo 
where there is a slight bulge out at the base of the wall.

Going back in time (above) I am working the wall from right to left and heading up the hill.
This is one of the best view points of the wall from the main entrance to the house,
so I was using my best stone here first as I had access to it in the stone pile
and before I used it in a less noticeable part of the wall.

I have started the terracing with the walls at the bottom of the hill
 and now I have access up the path to the stone pile in the upper left hand corner of the photo
and a place to work for this new section of wall.

Please refer to the earlier posts to see the before photos.

In the next photos you will see how I build the wall over the uncompleted section above 
and continuing to the left.

Also above you will notice the roots from a nearby Juniper tree.
I always try to protect the roots of trees, especially anything over 1" in diameter,
even to the point of changing direction of the wall where possible.
One advantage to having a flexible wall system.

The part that I have added above is actually two upright stones 
though the photo makes it appear that there is one.
Notice how three sides slope in from the face as they go into the wall,
This makes it easy to find adjoining stones
and is the reason I wanted to use the configuration of these 2 stones.

I will often put groupings of stones that fit together well at the stone pile
and then move them to the wall when I see an  opportunity.

Now I have broken a cardinal rule here by standing these two stones upright 
rather than have them extend into the wall by laying them down flat.
I plead guilty but this is a good example of how when building a dry stack wall 
we are constantly faced with decisions that break the rules
 but yet we still can have a solid wall.
How we deal with these is one of the differences between the owner builder 
and the professional waller.
As we go on you will see how I dealt with this.

Also this brings up the point of whether to have a foundation and if so how deep.
In the semi arid climate that we have here in northern New Mexico (USDA zone 6), 
the lack of heaving soil resulting from wet, frozen conditions led me to decide against a foundation.

In the past when working with wet or expansive clay soils 
I have used a ruble fill foundation that extended below the frost line,
and incorporated the foundation as a french drain to deal with water problems.

Every situation is different but the key variables are soil, moisture, and temperature.
Unlike a mortared or concrete wall, a dry stack wall is very flexible and is designed to move,
so some movement from frozen ground shouldn't be a problem.
We will look at this further in a future post on the theory behind dry stack walls.

In the photo above I have set the face stones about 6" below the finished grade
and before I fill behind them with ruble I will dig out the dirt behind a bit more.

I like to fill in behind the wall with ruble as I go as you can see above.
I generally start with the larger ruble on the bottom
 and as I work up to the top of the wall the backfill stone get smaller. 
I pack this fill in very carefully trying to get a good tight fit locking the wall together.
Remember these backfill stones are stones that I have previously set aside
 into the ruble pile as having no value as face stones.

(I tend to use the terms ruble, fill, backfill, and hearting interchangeably
to denote the stone that is packed in behind the face of the wall.)

At the base the wall is about 2'+/- wide and both the front and back of the wall 
will taper in to 1'+ at the top.

Also above, note that I have added a stone on top of the two narrow base stones 
I just put in the proceeding photo that extends across the width of the wall.
The point is that not every stone will extend across the width of the wall,
but you want to have as many of these cross stones as possible. 
This one was a great fit and really helped to tie the wall together.

As I mentioned earlier, notice here how the top of each stone you set in the wall
 should slope downward as the stone reaches into the wall,
 so that the next stone on top will want to slide into the wall - not out.
This causes the wall to tighten into itself over time.
This is very important and we will look at this further in the post on theory.

In the photo above I am just in the process of getting the flat stone set 
and chocking underneath with ruble for a firm set.
I will keep pushing smaller stone underneath till I have the voids filled in.

Most of the stone I used here have been chiseled to fit.
to see the chisels and mallets that I use)
I rarely try to shape a stone with the chisel but merely trim the stone to get a better fit.
This particular basalt though very hard and dense chiseled very nicely, coming off in nice flakes
and it had little grain to it which makes chiseling much easier.

Of course all stone is different and once you have worked with the stone
 you have at your disposal you hopefully will fall into a pattern 
of how it will respond to chiseling.

In general chisel off small sections at a time,
 and work back slowly to the line you have established to chisel to. 
Direct your blows to the center of the stone, a point that took me a long time to grasp.
 In essence if the force of the chisel is directed towards the mass (center of gravity) of the stone
 you are more likely to control the break and not break off more than you want.

There are many wallers who don't chisel at all 
and then there are those who will use grinders and saws to drastically alter the shape of stone.
I try to minimize my chiseling and yet I can easily spend an hour 
fitting and chiseling a stone until I am satisfied.

Now I have added the taller stone which will be the top of this section of wall.
It sits right behind our flat stone and I have enough hearting (or backfill) behind it to hold it secure.
You may remember this stone from the first photo in this post showing it's face.

I am working on the stone directly behind it 
that you see sticking out of the wall in the above photo.
I have just gotten it onto the wall off the hand truck and am getting ready to set it.
This is also the top of the wall.

Now we are looking down on that stone sticking out...

…and now it is set.

Looking over the wall note how the stones now are reaching well into the wall,
creating a strong wall as I mentioned above.

The backfill is being carefully packed in as I go along
and gets smaller and smaller as the wall gets higher.
You may notice the chips from chiseling 
and other small stones that I am collecting as I go along 
at the bottom of the above photo to be used in the hearting in the top of the wall.
Nothing goes to waste and actually I am always running out of smaller stones 
and hearting material before anything else.

Another very important point is to lean the wall into the embankment as you build,
something that is often referred to as batter.

This section of wall which is 2' to 2 1/2' +/- high has a batter of  3 to 4" per foot of rise. 
For my walls the batter changes quite a bit but a minimum of 1 to 2" per foot of rise is essential
 and I try to err on the side of too much is better than too little.
Call it extreme batter.
I will discuss this further in the post on theory.

In the photo above it is easy to see that the form I use is rather free.
I try to let the landscape and the stone determine the course of the wall to a great extent.

This may not appeal to every person or be appropriate for every situation,
but it works for me and particularly in this situation.

The style is not unlike the limestone farm walls from clearing field stone 
that are common in parts of the Shenandoah Valley and along the Blue Ridge Mts. in Virginia.

Retaining walls are much easier to build than freestanding walls.
There is only one side of face stone as the other side will never be seen.

As I have worked my way from right to far left the style is changing 
from a nicer, tighter wall with larger stone to smaller stone, looser fit
 as I transition from a highly viewed area to one that is more out of the way.

At the same time I have used the nicer, larger stone from the pile where they will be more prominent
 to now when I have only smaller stone with a slimmer selection.
Try to plan which stone to use where.
Again nothing goes to waste.

I regret that I didn't have a better supply of large flat stones from the pile to use as cap stones.
As it is potential cap stones also make great steps and pavers, and get diverted for that end.
A good cap stone helps to hold the wall together and gives a nice trim appearance.
I hope someday to come back and add a cap to this wall if I can find a suitable stone.

As it was, I was left with smaller stones than I would like.
When constructing the top of the wall make sure your stone reach well into the wall
 and are secure from falling out or becoming dislodged over time.
Use your hearting to lock them tightly in place.

In the next post I will take a more detailed look at the theory behind dry stack stone walls.

The posts to date in this continuing series are: