EDIT: After asking for some help, I decided to make a separate instructable for the bench and change the name to "flagstone backyard patio".
The whole project took almost a week to finish. Ever since last summer I was thinking to improve the looks of the backyard of my parents' house. So I decided to pour some concrete and install some beautiful asymmetrical stone tiles. When I got home for Spring break from my University I immediately started working on the yard.
Let it be noted that I am Greek, so English is not my mother tongue. Thus, please excuse my mistakes. Thank you!
WHAT WE ARE GOING TO NEED:
-A helper or two
So let's start
Step 1: Preparing the site-Pouring the concrete
I decided to build a "frame" of concrete to hold the stones inside the area, so I started with that. I used many different wooden planks and pured concrete inside of them. I measured carefully the dimensions of the yard I would like to have, and then put the wooden planks. In order to make them steady for the concrete, I nailed them on wooden spikes I put on the ground. For the planks to be on the right height i used a level and my measure tape and I had to dig some dirt to put the planks in the right place.
I made the concrete with the help of my father. It was just regular conrete mixed with sand and some gravel to make it stronger. We mixed it in the wheelbarrow, because we didn't have a concrete mixer. After that we poured it in betweeen the planks and straightened it. We let it for a day to dry, pouring water every few hours on the surface so that it wouldn't crack.
DIMENSIONS: The frame was 20cm in width and had around 8 cm of height. The overall area was about 10 sqr meters ( not much, but I used plain conrete and gravel for the rest of the yard)
ATTENTION: You want to know in advance where do you want the rain water to head. Every time you pourconrete you have to be aware of the slopes. You do not want to have puddles of rainwater in the middle of the sitting area, so be extra careful with the level. It is, however, almost certain, that no matter what you'll do, there is going to be some puddles of water. The tiles do not have a completely even surface
The stone tiles are used mostly to what I know to be called "crazy paving". Although, I used here a diferrent technique. The gaps between the tilew are far larger, and the tiles themselves are different. They come in a variety of colors, mostly black, drey-green and blue.
Step 2: Filling the area with sand
The next day we removed the planks and put regular sand mixed with 10% of cement in the cantral area of what I called as "the frame". We could have put conrete in the whole area and then put the stone tiles on the surface, but for that you would need more professional tools and experience than we had. Plus, the stone tiles where pretty heavy and there was a great chance for some to sink deeper in the conrete than others, which would result in a completely uneven surface.
Instead, I put regular sand, mixed with some cement ( around 10% of the overall volume of the sand) to make it stronger. If the sand at the bottom of the tiles wasn't strong enough, then the tiles could have subsided in the futere from the excessive wight. As a result the concrete would crack. I didnt fill all the area with sand up to the top, but I left a few centimeters (The height of the tiles) for the tiles to be put. I watered the sand with the concrete and let it dry.
Step 3: Placing the flat Stone tiles
Before putting the tiles in place I carefully cleaned each one of them with a wired brush and water to remove all dirt and loose parts. I mixed some more concrete and I started putting the stones in place. Using my tools and the strings I had put the previous day, started installing the stones.
First, you put a little conrete on the sand surface and then you put the stone tile on top of that. Using your tools and level you carefully hit the stone with the wooden part of a big hammer, until the stone levels with the conrete "frame". The concrete must not be too dry, so that the stone is going to stick well. You shouldn't put a great amount of watr either, because the tiles woulnd't be able to stay on a watery surface
It is better if you first devide the area into fours, and start working each one seperately. Use your imagination and puzzle skills to put the stones in the right places. The distance among the stone tiles can be as much as you want. But keep in mind that the stones must not touch each other, or be very far away. 3-4 centimeters is just right. Every now and then back out and look the floor from a distance. Picture in your head what you should do next.
Be carefull not to step on the tiles until the conrete becomes completely solid, because you can accidentally sink them lower to the ground.
Step 4: Finishing with concrete between the gaps
To finish the yard you have to make more concrete using very thin sand. In order to make the concrete extra strong you must put more cement powder in the mixture (the mixture is half cement, half sand )
The conrete must be quite wet ( not too much liquid though) in order to reach to all places between the stones. You can use a plastic bottle or a plastic cup to pour it efficiently between the gaps, and then after letting it dry for a few minutes you can use a regular wet brush to make it even. When you cover all the gaps you are done. (almost)
Naturally the concrete is going to cover parts of the stone tiles in the process, so when you finish you have to use a wired rough brush to clean them again and reveal the stones under the concrete.
( You wont cover them entirely of course,but some parts are going to get covered)
You must clean them while the concrete is still fresh. to avoid extra work. After a couple of days, the concrete is as strong as a rock. I washed the floor with soap to remove all the cement of the stone tiles and make them shine. I had to do this more than once, because, naturally the cement has changed their color.
To finsh the rest of the yard, I also put gravel around the concrete and planted some flowers.