The ring board.

Next we filled all the open spaces between the gravel boards and posts with a mortar mix. This was tricky the gaps where quite narrow and deep. A pair of trowels were great for cutting thin slices of mortar and slipping them into the gap. Next we were ready to install our ring beam. I had purchased some 3x2 treated timber and was going to screw this down broad side to the post tops. Drilling down into the post tops took some time and you have to be careful not hit the steel reinforcing bars. Use a good masonry drill and take it steady don't let it get to hot and ruin the drill. I had some masonry screws the type that don't need plugs just drill the right size hole and drive them in. These are amazing fixings and pull up tight with very little effort. The timber had to be joined down the long sides. Rather than mess about with any fancy joints we just splinted it with a 2 foot piece of 3x2. After we got all the way round I installed some 90 steel brackets to further secure the corners.

Up up and away.

I had obtained some scaffolding boards and concrete blocks in order to construct a safe work platform. The platform made the lifting and inserting of the gravel boards much more manageable.
As each gravel board went in I placed a thick bead of frame sealant along edge of the board. This was done to provide a water and wind proof seal between the boards. We also inserted more packers to wedge the gravel boards firm. Rather than completing an entire section all at once we worked around and built it up gradually. This ensured we didn't push out any if the posts more than any another. One section was a bit tight so we carefully spread the gap with a ratchet strap and after the first board was in it all fitted nicely. Progress was quick and soon all the boards were in place. Next we marked around the post tops with a black marker and cut them all off level with the final gravel boards. I used a angle grinder with a good quality diamond disk. I made several cuts in each working towards the middle. The end result was good clean and level. I think having a good disk is vitally important.

Base time.

I wanted the shed to have as large a capacity as possible. This ment a thin but strong concrete base.
Before any concrete went in we lined the bottom with 2 strips of chicken mesh. I thought this would make it less likely to develop any cracks.
We used some stuff from J B Little Woods in Sutton Scarsdale. I purchased a 50m x 1m roll for under £50. I wasn't going to use this much but the stuff always comes in handy. This shop is great for all sorts of bits and bobs such as nuts and bolts, garden tools and steel supplies. They also sell wooden posts weed killer etc. Prices great.
Next we made a wooden tamp out of some old timber. This was made so it would hang down of the gravel boards and guarantee a good level finish.
Now we were ready to start mixing. 5 parts lime stone 1 cement measured in buckets to ensure accuracy.  We had decided to hire a cement mixer and it was a good job we did. Mixing over 2 ton on a board would have taken a huge effort and the result would never be as good. It only cost £8 for the day, bargain. The mixes ended up quite sloppy and we had to add water sparingly.
The loads were barowed into the base and we just had about enough to get a good covering. As the loads went in we used the tamp to compress and level the concrete. You have to take time and care with the tamp working a bit leveling and then scraping. The surface was the floated up to smooth finish.
Before leaving the base to set we sheeted it down with a trap incase it should rain.

Time for a little hardcore.

I had a lot of broken up bits if rubble to place in the bottom. A hammer was used to smash up and compact it down. I was only going to cast a shallow concrete base so it was very important to ensure the ground was firm.
After the rubble I spread some crushed lime stone into the cracks and compacted further.
Shuttering was placed across the open doorway and held with wooden pegs. We were now ready to cast the base. I left it for a week to settle some more.

Leveling the gravel boards.

It was important that all the gravel boards be level relative to each other. One was chosen as a datum. We checked it was level in the horizontal and checked we had enough space to get the remaining boards in.
We then wedged the board into the post from the back. Several slices of mdf were tapped  in with a hammer and this effectively locked the board.
The ground was firm but with the huge weight of the remaining gravel boards forcing it down over time we had to be prudent. To ensure the board could never sink into the ground a quantity of concrete was inserted under the board along its length. Next we marked a line around the post using a set square and this allowed us to line up the next gravel board. To set the ends a spirit level was used and soon all the boards were on the same level and wedged in place.

How to square up.

Next we moved to the next corner. This had to be set at 90 degrees to the existing posts.
To achieve this we used some pythaguras theory. In a right angled triangle the length of the longest side is known as the hypotenuse. It's length squared will always be equal to the sum of the squares of the other two sides. H x H = (A x A)+(B x B). You need only to know any 2 lengths and the 3rd can be calculated exactly.
To get our right angle we measured the length of the original marking line and placed line out from this to a length of 5m.we then calculated the length of the hypotenuse. This was joined back to the other side to form a perfect right angle.
Sounds complicated but easy really. On such a big scale as this it is the only
The corner post was installed on this new line. We then created another triangle to give us our last corner and then simply joined the 2 new corners with a line.
The best way to check a rectangle for square is to measure It's diagonals. If equal it is square. The structure was found to be out only by 1cm. Not bad considering it was nearly 6m in length by 2m wide. I was very pleased.

The tricky corner.

The next post was another corner. The ground around this post was lower than the others so we had to create a shuttering to help support it.
This was made out if some old deck board and held together with screws. The shuttering was filled with concrete and broken bricks.
The shuttering was to be buried so it didn't matter much what it looked like. It just had to support the post well.