-
Welcome to our blog, Menfranco general blog
and this post, building the hybrid rock wall
-
Building the hybrid rock wall
Building the
hybrid rock wall
Dear readers, as we have said in our previous post, in this
post we are going to describe how to build a hybrid rock wall. Now, this hybrid
rock wall that we are going to build is really a big job if you are going to do
it yourself and you are not a tradesman, however it can be done if you follow the
way that we are going to describe here under.
So let us repeat briefly what we had done before, so that it
is easier to follow our next move; as you know we have dug in the yard because
we needed some room and now we are left with a bank in the backyard that needs
to be held back from a retaining wall. This retaining wall that we are building
will starts at ground level at its lowest point, as we have dug the ground
approximately level, and then follow the natural ground, because we are
building the wall only to the height of the natural ground level, it is going
to start from almost nothing and at the highest point will be 1.8 meter, it is
really two walls that meet and forms a square angle at the highest point.
Here we have to say that this retaining wall that we are
building, some people might think that this cannot or should not be done, as
this is neither a rock wall nor a concrete masonry wall, as it mixes about
everything, but so what, if it is convenient, why not do it? I have to say that
in my life time I have built walls like this with whatever was available on the
site; and I mean everything in fact I was using stones that were laying in this
small creek bed and pieces of concrete that we had broken to do some alterations
and old bricks, some concrete and some mortar, this has happened a few year ago
and last time I have seen the owner he said that the wall is still there. So,
most things can be done as long as you know that it has got a good chance to
last a long time.
Let us go back to
build our hybrid rock wall, first of all to build this wall you need a few
cubic meter of rocks, because you want the wall to look as a rock wall, you
don’t need very big rocks or special size rocks, because you can use the cement
wherever necessary to fill the gaps and this might be good, as the rocks could
be less expansive, you need a mixer, you need some gravel, sand and cement; and
of course you should have the tools to do the job.
You got all this on site and you can start to build. First
of all drive a couple of pegs in the ground, exactly where you wand the face of
the wall to be, tie and stretch a line on these pegs and see any adjustment
that you need to do before you start laying the first stone. What you are
looking for here is that the bank you are going to build the wall against has
been dug straight, it is almost vertical or just a few degrees sloping, you
have also dug a shallow foundation as you want the wall to be strong enough to
last for a long time, so you are satisfied that the foundation is going to be
solid enough, since it is well below the original natural ground, and therefore
can hold a lot of weight and pressure, even though you have dug it out one
side, the ground is very compact.
You have done all that you have set the pegs again so that
your wall is set to be about 10” thick overall, you have chosen this thickness
because most of the large rocks seem to be that thick, so now you are ready to
lay the first course of stones, mix a few batches of concrete and lay it in the
foundation and then before this concrete sets lay the first course of stones on
this concrete making sure that the bottom of the stones are below ground level,
so that the entire stone wall seems to start from below the ground; once you have
done that you can fill the back of the stone with concrete a bit above ground
level but below the full height of the stones, because you want to leave enough
room to lay next course of stone easily. Now the wall is all set to go, but we
need to reset how we have to continue and complete the hybrid rock wall, the
right way with the right lean against the bank, yes you heard it right the wall
is not going to be plumb, it is going to lean. You need to lean the wall
against the bank, so that the weight of your wall by itself adds strength to
the wall.
-----------------------------------
Completing
the hybrid rock wall
What we need to do now: first of all we are going to set up
how much lean against the bank we want, before we build this retaining wall,
here we have to keep in mind a few things before we definitely decide that;
first of all we have to consider how tall and how thick is the wall, we don’t
want the wall to lean too much and rely only on the dirt behind it to hold it
back, but at the same time we want to lean it against the bank so that the
weight of the wall is used to hold the dirt back.
Here one has to go back to look at what happens if you leans
a certain monolithic object to the point it is going to fall; what happens here
is that the monolithic object is going to fall, only after its centre of
gravity falls outside the area of the base. Now we don’t want to go this far
and we don’t want to use the centre of gravity for a few reasons, but we are
going to lean the wall about two third of the thickness, so that the very top
layer is still vertically one third of its thickness above the base; we believe
that it is very safe to go only this far and the wall would stand up even if we
don’t backfill it. Anyhow in our case we are not going to backfill anything,
because we have cut the bank exactly as the wall is going to be, you see we are
going to use the bank as a template, so we believe that we are not going to
backfill it at all.
Now that we know how much we are going to lean the wall, we
are setting a leaning profile on every corner leaning approximately 10 to 12
centimetres per metre and we are ready to resume building our hybrid rock wall.
But there is still another important thing to work out; you see we need to make
sure that when it rains the water that seeps behind the wall can run out, so we
have to leave a way to drain this water out and at this level is the right
place to do that, so we choose a few spots about a meter apart and mark them,
then when you lay next course of stones make sure that you leave a space
between the stones that the water can run out, you also have to leave the back
free of any abstractions for a course or two around this space, so in this
space after laying the front stone, just lay some smaller stones dry against
the bank to stop the concrete blocking the drain, then you can resume to
concrete the lot. Alternatively you could lay a few short pieces of pipe across
the wall for drainage, but you have still to make sure that they are clear of
any obstruction at the back near the bank.
So now you can go back to mix some cement to lay your
stones, you can mix a batch of river sand four to one that you can lay between
the rocks to give them a bit of grip, you are laying the rocks in a straight
line that you have tied on the profiles, when you do that make sure that this
cement does not come too far forward, because you still want the rock wall to
look like a rock wall, at the same time do not forget that you have to leave
these spaces with no cement at all for the seepage where you have marked, after
you have used the batch of river sand and cement and laid say a course of
rocks, you can mix one or two batch of concrete to fill the back of the stones,
then you repeat this procedure until you build the entire wall.
At the top of the wall, because the wall in not going to be
level, you may have to do some adjustment to follow the height of the ground,
here you have to use just common sense the best way you can finish, if you
happen to have enough wide and long rocks that can be used for a coping, use
them to finish your wall, if not, just use your common sense and use anything
that is available, even if it is going to be a strip of concrete in the back of
the wall, so that all the wall is tied up.
I hope I have explained well enough for you to follow my way
of building this hybrid rock wall. Here I would like to add that this is just
one way out of several other ways that can be used. A lot depends how the bank
has been cut and if it follows very closely the shape of the wall, so that you
can use it as if it is formwork, but if there is going to be some back filling
to be done, you may have to consider some temporary formwork that can be easily
removed before you backfill. All this things can vary from job to job, and if
you see that it would be hard to build your hybrid rock wall, then you have to
consider other ways to build your retaining wall.
Of course there are several more ways of building retaining
walls, some of which we are talking about in our next post, as this post again
is becoming too long, and also what we are going to write next is a bit
different from what we have written now. So see you next time, in these
retaining walls.
---------------------------------------------
This is:
Menfranco general blog,
Building the hybrid rock wall
IS TO BE CONTINUED;
Next time with, these retaining walls
-------------------------------------
Some personal and religious links:
Some personal and religious links:
No comments:
Post a Comment