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the yesyes observatory - the build


yesyes

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This is it!!! Today is the day!!! I have started building my observatory. :grin:

many of you may have followed my planning thread here:

http://stargazerslounge.com/topic/167847-the-yesyes-observatory-let-the-planning-begin/

Today I have cleared the site (moved most of the remaining stones to the front of the garden), started digging for the foundations and started building the shuttering. I managed to get 2 holes dug and shuttering build.

Pictures:

1 - shows cleared site

2 - first hole dug. due to the way the fences are not really square this is the reference point for measuring where the other foundations go.

3 - I hope that's deep enough

4 - this shows why this hole is the reference hole. the length of timber is perpendicular to the fence at the back.

5 - some more exact measuring than before. that is why most of the stones had to be moved.

6 - I'm beginning to get an idea of the obsy size.

7 - the foundations on the right need to be quite high so that the floor clears the tree stump.

8 - second hole dug, not quite as deep as the other one, the bottom is very hard there, I hope that is the level I can put the foundations on

9 - starting to build the shuttering

10 - using some old furniture boards I had lying on the loft

11 - first shuttering done

12 - and both done

That's enough for today... :smiley:

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Looking good Chris. Pleased to see you off to a sunny start! You're a bit ahead of my build - I'm still at the design stage, but hopefully won't be long before I get the spade out. Best of luck with your build, I'll be following it closely. :smiley:

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Looking good, have you left enough space to access all 4 sides from outside?

No, the site is not big enough for that. I will have to build the wall as panels and clad them before installing them in place. That's also why I'll be using UPVC cladding, no maintenance required...

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There are sellers on ebay. Search for sofit board.

The sides and the back will be just white as I won't see it anyway. For the front I will probably use wood effect uPVC. It's quite a bit more expensive than the white ones.

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More progress today...

First I measure everything so it's all square and level (hard to show on pictures). Then I dug the 3rd hole and build the shuttering, then dug hole 4. Didn't get around to build the 4th shuttering. BBQ tonight as a reward... :-)

Pictures:

1 - hole 3, there's some foundation from the wall I removed, I was able to undercut it a bit, so this might actually be a good thing that it's there

2 - 3rd shuttering in pace

3 - 4th hole - this is actually right on the roots of that tree stump, I hope that won't be an issue when it starts decaying... Any suggestions???

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I could use a bit of advice on that 6th foundation. It would need to be right on the edge of that concrete slab, not overhanging the slab at all.

Can I just pour the concrete into a shuttering that I build on top of the slab? Will the new concrete attach to the existing slab?

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Chris, I don't think you'll have any problem sticking the new to old. As Gina says, just make sure it's well cleaned and I'm sure you'll be OK. How thick is the underlying concrete? If it's substantial, and has been there a long time, it should make a solid base in my opinion.

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Hi Chris - looking good. To bond your new to old concrete you should really provide a 'key' to the old surface by going over it with a chisel to make sure any weathered concrete is removed. You can also add a little waterproof PVA wood glue to the new mix, that also helps tie the two together.

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Thanks for the suggestions...

I'll chisel the surface off as much as I can. Francis, you mean mix some PVA into the bottom layer of the new concrete? how much, roughly?

I have no idea how thick the slab is. From the side it looks like at least 3-4 inches, might be thinner towards the middle though... It looks like it's been there for quite a while...

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Today's progress report.

The original plan was to dig all holes and build all shuttering, then fill with concrete. Last night I suddenly realised that the furniture chipboard I use for the shuttering might not want to get wet when it rains. So today I have filled the first 2 foundations with concrete instead of making more shuttering. Also, I've found some long narrow pieces of metal on the loft. I decided to use them as strapping. Not sure this is strong enough though. Worst case I can just break / cut them of above the concrete. I had nothing to lose... :-)

Pictures:

1 - first foundation almost filled

2 - strapping bent

3 - first foundation filled and strapping put in. For the top layer of concrete I used just sand and cement to make it smoother. that's 11 bags of ballast, 1.5 bags of cement and half a bag of sand in there!!

4 - everything is hand mixed :-)

5 - 2nd foundation almost filled

6 - 2nd foundation done (9 bags ballast, 1.5 bags cement, 1 bag sand)

7 - I had a bit of concrete mix left, so I filled it onto hole 3 and put some rough pieces of old mortar from the removed wall on top

8 - both filled foundations

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Thanks for the suggestions...

I'll chisel the surface off as much as I can. Francis, you mean mix some PVA into the bottom layer of the new concrete? how much, roughly?

I have no idea how thick the slab is. From the side it looks like at least 3-4 inches, might be thinner towards the middle though... It looks like it's been there for quite a while...

Chris - so long as you remove the 'greyness' that normally builds up on old concrete you'll be fine. You can always just give the chiselled concrete a liberal coat of PVA and pour the new mix over before it dries - that works! What your doing is getting rid of any lichen or other growths that may have embedded in the top of the concrete as they will break-down once you new coating is applied and you'll have a weak layer. Probably not too bad with our applications but best practice is to 'clean' any old concrete in prep for the new.

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I just noticed that heavy rain is forecast for tomorrow. I covered the filled foundations and also the empty shuttering. Hopefully that's good enough.

How long till rain is not a problem anymore? And how long should I wait before taking off the shuttering? A week?

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Hi Chris,

You're making some great progress there... it's making my back ache just thinking about the work you've done.

Thanks for sharing. I'm new to the forum but these build threads are excellent reading and even better inspiration.

Shane

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How long till rain is not a problem anymore? And how long should I wait before taking off the shuttering? A week?

I would give the concrete a week to go off before removing the shuttering. It might be ready sooner, but best play it safe :smile:

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Chris, Keep your concrete covered and if it gets hot-n-dry :eek: then water it. Concrete doesn't fully cure for about a month but is best if it doesn't dry out too fast. Shutters off in a week should be fine.

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