Astrokev's ROR - The Build

[smudgeball]

2 hours ago, Astrokev said:

so fingers crossed.

I was so happy when the guy I work aside lent me his.

15 bags of concrete by hand, no thanks.

[Astrokev]

Tell me about it! 

I hand mixed 30 bags of ballast + 6 cement for the footings  - spread over several weekends mind!  All over now though - hooray!

[smudgeball]

I consider myself trumped in the concrete mixing dept !

At least I've finished

[Astrokev]

After removing the shuttering from the last foundation block, today saw me start on the pier. First came digging the hole.

I decided on a 750 x 750 x 750mm hole for the pier block. This was harder than I expected. After the heavy rain recently, the ground was soft enough, but it was difficult to wield the spade once the hole got below about a foot deep! Ended up using a garden trowel to scoop up the last bits of soil into a bucket. I was also getting close to the water table, so it was really sticky down there. Glad to finish it!

Here's a few pics of today's progress.

I now need to figure out how to hold my air-con tubing in place, and at the correct height, before filling with concrete. What have other folks done to achieve this?

I'll probably use some rebar (when I find out where to get some from) hammered into the ground to try and create more anchorage for the block. Not sure if this is necessary, but I reckon better safe than sorry.

 

[Bizibilder]

I didn't bother with rebar for my pier block but I did "hollow out" a couple of inches deep all round the base of the hole to that the bottom of the block was "anchored".  i have no idea if this was a good idea!!!!    However my pier is solid enough after about eight years in the ground.

[wimvb]

I don't think that rebar into the ground will help much, adthe it's too easy to bend tohelp with anchoring. But definitely use it inside the block & pier. Any diy store that sells concrete will also sell rebar rods in different sizes.

[smudgeball]

Have you not got this finished yet ?

I didn't use any rebar in mine but I'm not going for a concrete pier.

I think as Wim mentioned, definately in the pier itself. My block was smaller than yours so it was just concrete without reinforecement.

I've just constructed my 7' x 5' peg base ready to take delivery of obsy end of September.

Neil

[Astrokev]

On ‎13‎/‎08‎/‎2017 at 17:34, smudgeball said:

Have you not got this finished yet ?

I didn't use any rebar in mine but I'm not going for a concrete pier.

I think as Wim mentioned, definately in the pier itself. My block was smaller than yours so it was just concrete without reinforecement.

I've just constructed my 7' x 5' peg base ready to take delivery of obsy end of September.

Neil

I'm afraid I tend to over-engineer most things DIY, so plan to use rebar in the block as well as the pier. Being at work during the week really drags out the progress .

I've found it surprisingly difficult to find a store that sells rebar - Wickes and B&Q don't seem to stock it. I think the local Travis Perkins may have some, so off there on Saturday. Also need to order delivery of endless bags of ballast and cement - too many to carry in the car without using up a tank full of diesel!

Also need to find a concrete mixer. Local hire shop may be the answer if I can't 'phone a friend'. Looking forward to the next stage. It'll be hard graft, but the end result will be the first bit of my build that will be visible when the whole thing is finished!

Kev

Edited August 15, 2017 by Astrokev

[wimvb]

Usually it's frost and water level that causes movement in the ground and shift of the block and pier. I would aim for getting the block deeper than frost will get during the winter months, and have the immediate surroundings filled with draining gravel, rather than sand or clay. A local builder should be able to give you advice on the best way to make the block and pier. It's better to over-engineer a pier than to 'under-engineer' it, but over-engineering will most likely also mean over-budget.

 

Good luck with the build

[Adam J]

On 15/08/2017 at 22:32, wimvb said:

Usually it's frost and water level that causes movement in the ground and shift of the block and pier. I would aim for getting the block deeper than frost will get during the winter months, and have the immediate surroundings filled with draining gravel, rather than sand or clay. A local builder should be able to give you advice on the best way to make the block and pier. It's better to over-engineer a pier than to 'under-engineer' it, but over-engineering will most likely also mean over-budget.

 

Good luck with the build

In the UK the frost will be unlikely to get deeper than 10cm ever mate. Rain / water course is a different matter. 

[wimvb]

1 hour ago, Adam J said:

In the UK the frost will be unlikely to get deeper than 10cm ever mate. Rain / water course is a different matter. 

You folks in the tropics. 

[Astrokev]

5 hours ago, Adam J said:

In the UK the frost will be unlikely to get deeper than 10cm ever mate. Rain / water course is a different matter. 

Indeed. Frost isn't really a major risk.

I live quite close to a river so, although the garden doesn't flood, the water table is probably quite high. I'm not sure there's much I can do about this. I don't want to move, and re-routing the river is probably outside my budget ;-)

I've taken on-board the various comments and think hammering rebar into the ground in the hole before filling with concrete should be effective at reducing the risk of the pier moving if I accidently bump into it in the dark (in addition to putting rebar in the pier, as suggested).

The image I have in my mind is like a radial root system of a small tree or bush. Having had to dig-up several of these over the years reminds me how solidly the trunk is held in place by only 4 or 5 main roots radiating out into the surrounding soil.

Kev

Edited August 17, 2017 by Astrokev

[Astrokev]

Haven't posted a picture in a while, so here's a screen grab of my SketchUp design (minus cladding of course). Hopefully the finished build will look pretty close to this

My SketchUp model has all the main elements of the build on 13 different layers, with everything dimensioned. This has proved really useful so far in serving as the blue-prints to take all my measurements from.

 

[smudgeball]

19 hours ago, Astrokev said:

should be effective at reducing the risk of the pier moving if I accidently bump into it in the dark

If I accidentally bump into my pier bolted on top of all of that concrete, and it moves......I'm going on a diet !

[Adam J]

It looks great, it makes me shudder though as I know how long it took me to do mine (3.5months) and its easily half that size.

[Astrokev]

Thanks Adam. If the finished obsy looks half like the SketchUp drawing I'll be happy! I'm sure something will crop up that requires some re-design, but so far so good :-)

No idea how long it will be before it's finished. I'm tending to do a bit each weekend, working around chores, family commitments and work. So long as I make some progress each week I'll be happy. would be good to get it finished before winter though!

[wimvb]

That's a very well thought out design for your obsy. I like the idea of the main roof sliding over the smaller roof.

Foundations are the most important to get right, so take your time for this. Once the floor is in place, you'll find that the next phase will go a lot faster.

Good luck with the build.

[Astrokev]

So, didn't get as much done this weekend as I'd hoped for.

Travis Perkins were able to sell me some lovely rebar yesterday. After finishing all my chores today I managed to find an hour this afternoon to start to fix the rebar in place.

Here's a SketchUp drawing of the plan for the rebar - basically, 3 lengths driven into the surrounding ground from the block, then 3 longer lengths forming a tall pyramid to strengthen the pier tube. The air-con tube I'm going to use will rest on 500mm horizontal rebar attached to the legs of the pyramid. The brown pieces in the drawing are the wooden frame around the hole to which I'll screw a top sheet of ply to stop the concrete spilling over from the weight of the concrete in the pier. 

In the image I'd only managed to attach 1 of these support pieces before the rains came (again - I'm beginning to wish I'd built the obsy in the winter when the weather should be better ). Will attach the remaining 2 horizontal supports next chance I get. Then I need to make a wooden frame to support the tube laterally to ensure it's vertical. Once filled with concrete, the tube will be pretty heavy, so need to make sure the wooden frame is up to the job!

 

 

[Astrokev]

5 minutes ago, wimvb said:

That's a very well thought out design for your obsy. I like the idea of the main roof sliding over the smaller roof.

Foundations are the most important to get right, so take your time for this. Once the floor is in place, you'll find that the next phase will go a lot faster.

Good luck with the build.

Thanks Wim.  I can't claim much credit for the design I'm afraid. I've pinched loads of ideas off other builders over the last few years. Most of the design is based on the build YesYes did a few years back.

Kev

[RayD]

Look forward to seeing it all up and running.

Edited August 21, 2017 by RayD

[Astrokev]

On ‎20‎/‎08‎/‎2017 at 19:59, RayD said:

Look forward to seeing it all up and running.

Thanks Ray....but I wouldn't hold your breath .

I'm hoping the end result will be half as good as your obsy - very impressive!

Kev

Edited August 21, 2017 by Astrokev

[RayD]

1 hour ago, Astrokev said:

Thanks Ray....but I wouldn't hold your breath .

I'm hoping the end result will be half as good as your obsy - very impressive!

Kev

Thanks Kev.  No need to worry there, looks like you're doing a super job and planning ahead well.  

[Astrokev]

After a few wet weekends, it's great to have some reasonable weather for obsy building

This afternoon I finished tying rebar to the pier strengthening rods, to provide a horizontal frame to support the tube at the correct height when I pour the concrete. At the moment the tube is resting loosely on the supports and is not yet vertical - I will build a wooden frame to hold it vertical.

Once the rebar work was complete, I made a simple wooden frame to go round the hole, with some shuttering at the back where the hole was too wide from where I dug up the path. I want to make sure the pier block is isolated from the concrete path that some of the corner foundations are sitting on.

Next job is to make the frame to hold the tube in position, and cut boarding to go across the hole to stop the concrete being pushed upwards by the weight of the concrete in the tube.

One question I'd value advice on - the bottom of the hole is quite wet and clayey (is that a word??) and is fairly soft. Would it be OK to pour concrete straight on top of this, or should I put some broken up hard-core or shingle down before pouring the concrete? I'm worried that the concrete block may sink into the soft clay.

Thanks in advance!

Kev

[smudgeball]

Morning

Looking good.

My hole bottom was a bit clayey as well.

I put a layer of gravel in and tamped it down before I poured the concrete. (more of a "felt it's a good idea to do", than having any technical authority behind it )

Neil

[Alan White]

Kev

Following the build with interest, the weather has not been your friend in this endeavour.

Just had a look at your website link, have you not updated it for a while or was it me, interesting images and story, very similar to my own but a few years adrift, you have managed more travels than myself to date.

What set up are you expecting to locate within the observatory when completed?

Keep on building and posting.