Astrokev

Big weekend - despite having to dodge several torrential downpours, I managed to finish my pier. Hooray! 36 bags of ballast. Thank heavens for the electric mixer, which made light work of it. I supported the air-con tubing with stud-work attached to pegs driven into the ground. After filling the hole, I screwed MDF sheets to the frame around the hole to prevent the concrete being forced out by the weight of the concrete in the tube. It was really satisfying reaching the top of the pier tube and "topping-out"! The pier top-plate is 16mm aluminium. I attached this to a temporary piece of MDF to act as a spacer and to cover the entire top of the tube to keep the concrete level, using stainless steel threaded rods. This went into the concrete easier than I expected, requiring only light taps with a lump hammer to get it to touch the top of the tube. The white tape at the top of the tube has a reference line which I matched with a similar line on the MDF, to indicate approximate true north. I'll leave this a couple of weeks to go off. Next week I'm at Kelling so won't be tempted to remove the supports and MDF prematurely! Glad the concrete work is finished. More enjoyable woodwork from now on .

Concrete mixer being delivered tomorrow . The plan is to install the air duct tube and make the supports to hold it in place tomorrow, then mix all the concrete for the block and pier on Sunday. Praying for dry weather

Thanks Ray. Yes, really looking forward to getting the pier finished. I'm on much more familiar territory working with wood! Kev

Thanks Roger. Don't have a blow torch that I can remember, but will be trying to bend the ends to prevent risk of twisting if I apply excessive torque. I'm using M12 stainless rods, so not sure how easy this will be - it'll give my vice and lump hammer a good work-out

After rescuing a frog from the bottom of the hole, today I added some Wickes sub-base (thanks RayD) to try and firm up the clayey base to the pier hole. I think this has helped, but it's still pretty soft down there. I also found a length of aluminium frame from an old bed during a clear-out of the shed. Perfect to add a bit more strength and support to the pier tube, so bashed that into the bottom of the hole as well. I'm fairly confident now that the pier will be pretty solid . Next job is to order a delivery of ballast, but I'm not sure how much I'll need - see my other post on this! Other work focussed on the pier plate (no pics yet). I realised that I'll need to push the threaded bar that will attach the plate to the pier into the wet concrete after I've finished filling the pier tube, so started playing with the plate and fixings to help me make a form to hold this in place while the concrete goes off. A few images before and after adding sub-base...

This weekends update - Family matters didn't allow much time, but managed a bit of progress on the pier. I made the sheets to put on top of the pier block once it's filled with concrete, to stop the weight of the concrete in the tube pushing the concrete out of the hole (no image of this yet). More interestingly, I cut a few holes in the pier tube and installed plastic drain pipe to carry whatever cables I end up needing, to prevent them trailing all over the floor - well that's the theory. The bottom outlet in the images will be below floor level so will be hidden. A pipe from this outlet will go to the warm room. I cut the top outlet in the side of the pier instead of out of the top, because the top plate I will be using may make it difficult to access the pipe outlet if I put it in the top. I also made 2 small frames to put around the tube (at top and bottom). These will be held in position to keep the tube vertical by long supports fixed to the frames and hammered into the ground. Here are a few images.

Thanks Ray and Chefgage. I think I'll be following your suggestion there!

Hi Alan Thanks. As you've noticed, I've neglected my blog recently. The hobby has taken a back-seat for the last few years for various reasons. Now I'm back into it, I must start posting again! My current set-up is a 10" Newt on an NEQ6, though I'm seriously tempted to upgrade this - not sure what to as yet, but a frac is probably on the list for wider field imaging, in addition to a longer focal length scope for planetary and lunar work. cheers kev

Thanks Neil.

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

Looking good. This design seems to defy the laws of physics!

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 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

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!

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!

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.

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

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

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.

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!

No picture tonight (getting a bit dark out there) but the good news is I've finished pouring all 6 footing blocks. Looking forward to the weekend when I can unveil the last one. Next step is digging out the hole for the pier block. This will be too large to mix concrete by hand, so will have to use a mixer. My son reckons there's a chap in the village who may be able to lend me his, so fingers crossed. I also need to give some thought to how I'm going to support the air con duct tube in the right spot and at the correct height. Looking forward to this bit, as I'll be able to start cutting some wood!

Footing block #5 finished . Torrential rain this afternoon so decided not to start on the last block - maybe tomorrow.

Thanks Roger. Sensible idea about the middle block - I finished concreting this today and certainly tried to do that . I guess I'll have to wait till I buy the joists to see how well I did. Here's an image of the finished block. I decided not to put metal strapping in this block. I think having the ends of the joist fixed only to the corner blocks should be sufficient. Rain forecast for later this afternoon, so polythene sheet at the ready! Five down, one to go! Getting a bit tired of concrete to be honest and can't wait till I start on the woodwork. I'm going to have to get a mixer for the pier block; I think it'd kill me mixing that amount by hand! I need to decide whether to hire, buy second-hand off flea-bay, or try and find someone to lend me one.

Next job is to make the foundation blocks in the middle of the two long walls to give extra support to the floor joists and spread the weight of the obsy a little more. I used the orange marking line to try and get the form aligned (I reused one of the forms I'd used for the corner blocks), levelled the form with my trusty spirit level, then fixed the form in position with 4 pegs hammered into the ground. Of course, having got the first block ready, the heavens opened and it didn't stop raining for the rest of the afternoon. Rain stopped play (again)

Today I removed the forms from the corner foundation blocks , and then measured the four sides, and the diagonals, to see how accurate the dimensions turned out. The 2 long walls were 9mm out. One was spot on at my target 3500mm, the other 3509mm The 2 short walls were 6mm out. One was spot on at my target 2300mm, the other 2294mm The diagonals surprised me, being only 2mm out! (4190mm and 4188mm). Overall I'm pretty pleased with the accuracy , which shouldn't cause me any problems, as I can overhang the floor joists by the 9mm and 6mm to make the base nice and square.