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Concrete Pier Preparation and Construction


Gina

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Started pouring concrete today. About a third of the foundation block. Probably be off out to get more ingredients tomorrow. It looks like I shall need something like 4-5 bags of cement and 16-20 bags of ballast in total. Just got cleared up and the workings covered up this evening when down came the rain - a thunderstorm!

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Started pouring concrete today. About a third of the foundation block. Probably be off out to get more ingredients tomorrow. It looks like I shall need something like 4-5 bags of cement and 16-20 bags of ballast in total. Just got cleared up and the workings covered up this evening when down came the rain - a thunderstorm!

There are loads of calculators on the web that will tell you how many bags of cement and ballast you need - Here's one for example

Concrete Calculator

a 1m x 1m x 1m block will require 2.2 tonnes of concrete !

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If you have a permanent set up you set the threads in to the concrete pier as you would anyway then drill a shallow hole in the center large enough to accept a 17mm bolt head. Get a steel plate (thickness depending on needs) drilled the center and 3 or 4 holes for the fixing studs. Fit the plate establish north and drill and tap a hole. Screw 3 nuts up a M6 bolt and the tighten in to the north hole in the plate for polar alignment. Remove the legs from your tripod and then tighten the mount/tripod to the plate using a regular M10 bolt with spring washer and fit flush to the pier. Any leveling needed can be done by sliding washers under the plate and once done tighten down solid. Doing it this way can mean a bit of fiddling to get PA and leveling correct but once done it shouldn't have to be done again.
I can reduce the impact of relatively small bolts to connect to the top plate by making them as short as possible (and maybe bigger).

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There are loads of calculators on the web that will tell you how many bags of cement and ballast you need - Here's one for example

Concrete Calculator

a 1m x 1m x 1m block will require 2.2 tonnes of concrete !

Thanks Malcolm :D Fortunately, a) The hole is a bit smaller than 1m cube (35" x 30" x 30") and :( I've got plenty of rubble to use in the bottom of the hole. OTOH I'll be using pure new concrete for the top of the hole and the pier. Useful calculator :p
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I hate to put a possible dampener on things but I'm pretty sure your supposed to poor concrete all in one go. If you pour another mix in on top you will end up with Lego bricks. You can stick them together but they easily be brake apart. SORRY :D

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Gina

As you are mixing as you go you will have some control over the concrete, I am thinking the flower pot/pier needs to be supported, possibly 3 or 4 legs fixed to the inside of the lower pot extending to the bottom of the hole, like a bar stool perhaps (or perhaps your studding to the pier head is doing it?), and something near the top to keep it level.

Concrete will push the pier around as you pore and tamp down, and as you fill the pier may try escape into the hole and overflow.

I may be looking for problems that don't exist, I can see a bowl of porrage with a paper cup floating on top. Am trying to be helpful:)

Like the pier head design, we used a 6mm bolt with a 6mm stud connector topside for the pin, had to take a corner off the top outside.

Mick - Jordan' dad

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I hate to put a possible dampener on things but I'm pretty sure your supposed to poor concrete all in one go. If you pour another mix in on top you will end up with Lego bricks. You can stick them together but they easily be brake apart. SORRY :D

Have to agree. Otherwise there will be a weakness at the layers. These tipup cement mixers can mix a barrow load of concrete in 6 minutes and only cost around £30 a week to hire. Should be able to mix enough to mount in one go

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Our cement mixer will take half a bag of cement and two bags of ballast (ie. 62.5Kg of dry ingredients) plus water. So far I've used 3 mixer-fulls. I shall get in what I think I might need plus and extra bag of cement and 4 bags of ballast - it doesn't matter if I get too much, we're always using concrete for something or other and have a couple of small jobs already in mind. Once I have everything ready I shall mix and pour continuously until the job's done.

I currently have 2 one inch galv water pipes and 2 rebar rods hammered into the ground in bottom of hole reaching within about a foot of the pier top. Then hanging down from a piece of wood, 4 M14 threaded galv rod to take the top part. I intend pushing these down into the pier concrete once full. The rods will overlap the other rebar by nearly 3ft. I was thinking of holding the bottom bucket with wood across to the ground outside the hole but I could instead bolt it to some builders galv bar and embed that in the concrete - probably more secure.

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Can we see some pic's please?

Ive been following this thread and it makes interesting reading. You definitely need to pour the concrete all in one go other you will end up weaknesses.

Ive just been totalling up some stuff for my obsy and was quite astoudned that for a 2.4 x 2.4 obsy i need about 3 cubic meters of concrete resulting in over 7,000kg of raw materials :D:p:( I think i need to revisit my numbers...

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Started pouring concrete today. About a third of the foundation block. Probably be off out to get more ingredients tomorrow. It looks like I shall need something like 4-5 bags of cement and 16-20 bags of ballast in total. Just got cleared up and the workings covered up this evening when down came the rain - a thunderstorm!

That's a shame you have to buy small bags as places like Dove do 'dumpys' of ballast which are ton bags and deliver them. I've been pouring concrete over the past few years and they're invaluable. Over 20 of them so far :p

Also, I found nowhere cheaper for bags of cement than B&Q, strangely. If you buy more than 5 they're super cheap and not even small outlets here can compete. Makes a change as B&Q normally isn't the cheapest.

Like the look of your pier adapter :D

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Can we see some pic's please?

Ive been following this thread and it makes interesting reading. You definitely need to pour the concrete all in one go other you will end up weaknesses.

Ive just been totalling up some stuff for my obsy and was quite astoudned that for a 2.4 x 2.4 obsy i need about 3 cubic meters of concrete resulting in over 7,000kg of raw materials :D:p:( I think i need to revisit my numbers...

Still preparing to build my obs, I thought it best to only have concrete under the pier area (36"x36"x36" max) to minimise thermal issues. Leaving the rest as a floating wooden floor above a layer of insulation and then the ground.

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I raised my pier by adding to the concrete "lump". I gave it a couple of coats of PVA and drilled and plugged the lump and set in 8 x 4" stainless screws to key the join....no probs so far.

I also re-epoxied the studs for the pier into the original block and cast around them.

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I'll take some pics when it stops raining though I have some of the hole whai I'll dig out.

The concrete in the bottom of the hole has 7 or 8 pieces of iron (rebar and scrap pieces) embedded in it and sticking out at various angles. This includes the 4 pieces that were hammered into the ground at the bottom of the hole and which go way up into the pier column. I think these will provide a pretty good connection between the two pieces of concrete. The top of the fill is very rough and ragged and should itself provide a good key.

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Regarding sources of materials, we have a Jewsons in Honiton about 5 miles away. The nearest B&Q or Wickes are just outside Taunton and about 13 miles away. Not sure about B&Q (usually too expensive) but Wickes charge £30 delivery for "Big & Bulky" as they describe these items.

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Regarding sources of materials, we have a Jewsons in Honiton about 5 miles away. The nearest B&Q or Wickes are just outside Taunton and about 13 miles away. Not sure about B&Q (usually too expensive) but Wickes charge £30 delivery for "Big & Bulky" as they describe these items.

I have no idea about B&Q's bulky bags but Jewson's is ok. Not as good as Dove's (Ballast). Wickes are decent but £30 delivery is way too much. Doves can be free if you sweet talk them (I have bought loads though). Or is that £30 delivered? Dove is about £30 for a dumpy so that sounds right.

B&Q are usually expensive...no doubt. But their Blue Circle cement is a cracking price when buying more than 5. Nowhere gets near...I travel to get it :D

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Regarding sources of materials, we have a Jewsons in Honiton about 5 miles away. The nearest B&Q or Wickes are just outside Taunton and about 13 miles away. Not sure about B&Q (usually too expensive) but Wickes charge £30 delivery for "Big & Bulky" as they describe these items.

Is there a Rawle, Gammon & Baker (RGB) anywhere over your way? We have one in Wivey and they deliver for free. It's possible they're more of a West Somerset company though I'm not sure.

As regards the bottom of the pier, I can't believe it will be a problem pouring it in a couple of goes when you have the metalwork binding it all together. It's not like plenty of buildings and other structures aren't poured in several goes with the concrete being allowed to start curing each time.

James

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As regards the bottom of the pier, I can't believe it will be a problem pouring it in a couple of goes when you have the metalwork binding it all together. It's not like plenty of buildings and other structures aren't poured in several goes with the concrete being allowed to start curing each time.

James

That is true but. One thing though, in this scenario, we factor in movement of structure etc, sometimes upto 20mm. Im guessing your not gonna want upto 20mm of movement when imaging....

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I've been working things out and yes buying 25Kg bags is very expensive. I started doing that because I had totally underestimated how much I needed. Now seeing how far what I've mixed has gone and considering that what's in the hole includes a lot of stones and lumps of old concrete I reckon another 30 25Kg bags may be wanted (plus 7.5 bags of cement). At those quantities bulk buying certainly makes sense.

Been on the Wickes web site and looked at prices. An 850Kg bag of ballast is about £39. Thats 34 25Kg bags worth. Jewsons cost £2.77 per bag and inc. VAT, 34 bags would cost £113. Including delivery, that much would cost about £69. Wickes also work out cheaper on cement too if you buy 5 or more bags at a time. So even with £30 delivery (per order) Wickes works out considerably cheaper than little bags from Jewsons. Not looked at B&Q yet.

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Been on the Wickes web site and looked at prices. An 850Kg bag of ballast is about £39. Thats 34 25Kg bags worth. Jewsons cost £2.77 per bag and inc. VAT, 34 bags would cost £113. Including delivery, that much would cost about £69. Wickes also work out cheaper on cement too if you buy 5 or more bags at a time. So even with £30 delivery (per order) Wickes works out considerably cheaper than little bags from Jewsons. Not looked at B&Q yet.

Thats exactly what Ive been looking at today :D At the moment I am working out all the quantities that I need and working out a rough budget price (current based on B&Q prices). Once I have this in mind and know exactly what I need I can shop around for the best prices.

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Ive just been totalling up some stuff for my obsy and was quite astoudned that for a 2.4 x 2.4 obsy i need about 3 cubic meters of concrete resulting in over 7,000kg of raw materials :D:p:( I think i need to revisit my numbers...

If you use that calculator, the last field is in mm not meters like the others ! - caught me out too !

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I've been working things out and yes buying 25Kg bags is very expensive. I started doing that because I had totally underestimated how much I needed. Now seeing how far what I've mixed has gone and considering that what's in the hole includes a lot of stones and lumps of old concrete I reckon another 30 25Kg bags may be wanted (plus 7.5 bags of cement). At those quantities bulk buying certainly makes sense.

Been on the Wickes web site and looked at prices. An 850Kg bag of ballast is about £39. Thats 34 25Kg bags worth. Jewsons cost £2.77 per bag and inc. VAT, 34 bags would cost £113. Including delivery, that much would cost about £69. Wickes also work out cheaper on cement too if you buy 5 or more bags at a time. So even with £30 delivery (per order) Wickes works out considerably cheaper than little bags from Jewsons. Not looked at B&Q yet.

Wow that's a lot of concrete !

Think I used around 10 bags at the most tho I bulked it out with bagged ballast and lots of steel rod. My pier is around 1 metre above ground with a 2 foot x 2 foot cube underground. I used stainless 10 inch ducting that was in a skip at work.

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