Gina's Observatory Build - Abbreviated - Site Preparation

[Gina]

This thread will describe the site and it's preparation for my observatory.

[Gina]

The site before any work was started :-

[Gina]

This was the site after my first (abortive) attempt at building a pier. I changed my mind about the size and position of an observatory and the pier construction I'd started was in the wrong place. Lesson here - make absolutely sure you're digging the hole and pouring concrete exactly where you want the pier.

My weather station Stevenson Screen and mast can be seen in the background. I've moved the rain gauge out of the way ready for preparing the site.

[Gina]

Digging out the site for the foundations :-

The ground is on a considerable slope so to avoid having a very high "shed" (with steps up to it) the ground needed excavating to a depth of 18" along the north side and about 10" along the south side. I'm using some 8" x 3" beams we bought in a second hand timber sale. They were main roof beams from big sheds and well seasoned.

There weren't enough of these to use as joists but they could provide strong support for joists on top and only need supports at each end. They weren't long enough to run the length of the building so were placed crosswise. We had 4 of these but one was flawed so I used three. This meant a length of about 6-7ft (2m) between supports for the joists.

I dug six holes some 12-15" deep and 18" square to take concrete foundations for the beams. Photos showing that later...

I used a Rotavator to break up the soil to excavate the main area and carted the soil away in transport box on the back of the tractor. The photo below shows the soil piled up into heaps ready to take away. The aborted pier diggings can also be seen.

[Gina]

Here's the soil removal. The red box at the back of the tractor lifts up on hydraulics, so you can have it on the ground and push soil into it, then raise it up and cart the soil away. In this case we wanted soil in another part of our property so didn't need to hire a skip or anything to get rid of it. I used the very substantial safety guard on the rotavator to push soil into the box Saved a lot of shovelling

[Gina]

This next photo shows a deeper excavation in the area of the pier base to lessen the depth of digging by hand. It also shows a problem I had at that time with rain making the diggings muddy and the soil very heavy and difficult!

[Gina]

And here's the pier hole dug out by hand another two feet lower. By this stage, digging well down into the solid clay level. Hard going but a really solid support for the concrete pier base.

In addition to the pier base hole (about 3ft deep and 27" square), I dug six smaller holes for the foundations to support the floor beams, as mentioned above. These were about 15" square and 1ft deep. Here are photos of two of them, one showing the beam end. I took these holes just as far as the clay boundary.

[Gina]

This next photo shows the three beams in position over the six holes, after being cut to length. One of the trestles used to support the beams for sawing can be seen too. The poor quality is because it was a part of the webcam image. The rain is evident from a couple of water droplets on the window of the waterproof box containing the webcam. We had plenty of rain in 2011 as well as last year!

As many have seen, this webcam was used to broadcast the whole observatory construction as it progressed and I'll be posting some more images from the webcam video footage to illustrate the build. (But not going overboard like I did in the big build thread )

[Gina]

Ordered 2 giant bags of ballast and 12 bags of cement to suit, for making the concrete for the pier and the six floor foundation blocks. Thought half that might have been enough but wanted to be sure. Also we had a few other jobs requiring concrete.

In the next photo five of the six floor foundation blocks have been poured, though only the nearest two can be seen clearly under the beams.

The piece of timber on top of the far two beams was used in conjunction with a spirit level to make sure the tops of the beams were all on the same level. The left hand far support being the last to be poured before this photo was taken. The spirit level was also used to make sure the beams themselves were level.

[Gina]

Here's a couple more photos of the beams and supporting concrete including a "canine inspection" Damp proof course was placed between the beams and the concrete blocks before the beams were properly fixed to the blocks using the wall ties that were embedded into the concrete blocks

[Gina]

The next part of the job was constructing the pier - providing shuttering and pouring concrete. This is described in a thread of it's own :- http://stargazerslounge.com/topic/172972-ginas-observatory-build-abbreviated-pier-construction/

[Gina]

This concludes the site preparation and foundations for the observatory. The next section is the timberwork which I've called the "Main Construction" :- http://stargazerslou...n-construction/

This post acts as a crossover to the main build and shows more of the foundations.

Having creosoted the beams and let them dry they were ready to be laid on damp-proof course on top of the concrete foundation blocks.

So suitable lengths of DPC were cut from the roll and set in position between beams and concrete as each beam was put in place.

Here is a close-up of one of the bases with the DPC. The wall ties set into the concrete to fasten down the beams

(in preparation for any hurricane that might come along) can also be seen more clearly.