Pier foundation quandry

[Adaaam75]

Hi guys,
Just a quickie, I've moved and am relocating my steel pier. So, would postcrete do a decent job for the footing of my steel pier in conjunction with rebar and 14mm threaded bolts? I'd make the hole big enough to cater for the size of the pier base and threads, I'm just purely asking if it will be strong enough as it is designed to hold concrete fence posts up with fence panels in the wind. The alternative is to mix concrete but if postcrete in the right quantity will do the job satisfactorily I'd choose that for convenience.

 

 

Thoughts please 🙂

Adaaam75

 

 

[WanderingEye]

Hmmm, me thinks not, I would not use it, it tends to crumble, as the water never really penetrates all through the mix because  it sets on the outside quicker...
I have just done a piers base, and only took 2.5 hours, to mix and pour using a large plastic tub, and a plaster mixing paddle...at 5-1 ratio...my block is 600mm square and 700mm deep...and I had to drill 18mm holes for the pier studs...

see here...

 

[johninderby]

Postcrete is good.........for posts that is but isn’t that strong. Bit from the tech info of Postcrete.

CONDITIONS OF USE
• POSTCRETE may be used for the purposes of fixing domestic posts.
• POSTCRETE may be used for fixing decking posts, rotary washing lines and small/medium sized gateposts (less than 1.0m width gate).
• POSTCRETE may not be used for general concreting, screeds, mortar, grout or render.
• If a specified compressive strength is required, POSTCRETE should not be used

[WanderingEye]

I would also like to add, that using postcrete is a very very expensive way of doing it too, as one 25kg bag is approx £5, I needed the equivalent of 30 x 25kg bags...which cost me £50, £30 for a half bulk bag of ballast, and £20 for five bags of cement..and I still have a load of ballast left over for another job.. 😀

Edited November 1, 2019 by WanderingEye

[upahill]

I love the stuff, wouldnt use it on its own though as a substitute for concrete. As WanderingEye says it never really penetrates all the way through and tends to crumble.

I opted for building a block of concrete using premade £3 blocks - was easy and seems very stable but if you are planning on being there for some time I would go for straight concrete pour - probably much cheaper and you wont be worrying about it everytime you bump the pier.

[johninderby]

I would add fibres to the concrete mix as it reduces cracking and makes for a stronger base.

https://www.toolstation.com/bostik-fibres-for-concrete/p27616?utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gclid=Cj0KCQjwr-_tBRCMARIsAN413WTa443Y84cYZJuTl2jbB9aYXtBmzU0ASStCfYKwx2NWChYQCmQtS7caAqvcEALw_wcB

Have you considered one of the companies that deliver small quantities of concrete for DIY projects? Should be a company like this in your area.

https://maximinimix.co.uk/?gclid=EAIaIQobChMIyoDbx7bJ5QIVFuDtCh2TaQq8EAAYAyAAEgL0afD_BwE

Edited November 1, 2019 by johninderby

[Adaaam75]

Well thanks guys, always worth jumping on and asking! 

I have found that when I've used postcrete for posts it needs a good mix (contrary to what the bag says!) to ensure there are no little pockets of powder but other than that I thought it would be strong enough contrary to what the guidance says that Johninderby kindly posted. The consideration i'd missed was the cost, having never mixed concrete before (assumed I have to use a mixer 🙄!) I thought it would be like for like in price but clearly not.

Another question then if I may...

What is the advantage of setting the concrete and then drilling holes for the threads? The only method I've seen until now was sinking the threads in the wet concrete using a template?

Should I use rebar or will the fibres above be sufficient?

thoughts again please....

Edited November 2, 2019 by Adaaam75

[Adaaam75]

16 hours ago, johninderby said:

I would add fibres to the concrete mix as it reduces cracking and makes for a stronger base.

https://www.toolstation.com/bostik-fibres-for-concrete/p27616?utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&gclid=Cj0KCQjwr-_tBRCMARIsAN413WTa443Y84cYZJuTl2jbB9aYXtBmzU0ASStCfYKwx2NWChYQCmQtS7caAqvcEALw_wcB

Have you considered one of the companies that deliver small quantities of concrete for DIY projects? Should be a company like this in your area.

https://maximinimix.co.uk/?gclid=EAIaIQobChMIyoDbx7bJ5QIVFuDtCh2TaQq8EAAYAyAAEgL0afD_BwE

Thanks John, will definitely use this now I'm using concrete 👍

[WanderingEye]

1 hour ago, Adaaam75 said:

Well thanks guys, always worth jumping on and asking! 

I have found that when I've used postcrete for posts it needs a good mix (contrary to what the bag says!) to ensure there are no little pockets of powder but other than that I thought it would be strong enough contrary to what the guidance says that Johninderby kindly posted. The consideration i'd missed was the cost, having never mixed concrete before (assumed I have to use a mixer 🙄!) I thought it would be like for like in price but clearly not.

Another question then if I may...

What is the advantage of setting the concrete and then drilling holes for the threads? The only method I've seen until now was sinking the threads in the wet concrete using a template?

Should I use rebar or will the fibres above be sufficient?

thoughts again please....

The reason I drilled and set bolts in with a special resin, is that it all came as a kit with my pier, as they are 16mm studs, if I were to set in the concrete, they would need to be bent, to stop them moving or turning in the concrete when bolted too, but if you have some studs long enough that can be bent, then yes, set them in the wet concrete, it would be easier I guess, I also already owned the mixing paddle for mixing the concrete, and a big heavy duty SDS drill for drilling the holes, if you don’t and can’t borrow them, then that would be extra cost hiring them...you won’t drill the concrete with any standard drill, I can assure you.. 😀👍

PS, I never added any fibres or rebar, not needed with a good strong 5-1 mix of ballast and cement...just make sure your block is big enough to have the bolts at least 100mm from the edge if drilling, if setting in, then that does not matter so much...

Edited November 2, 2019 by WanderingEye

[johninderby]

Fresh concrete isn’t that hard to drill. The concrete gets harder as it gets older. Try drilling 50 year old concrtete sometime. 🤬

I use my cordless SDS drill and it makes a huge difference over trying to use a standard drill even if it has hammer action. 

Adding fibres isn’t needed for strength in your case but a good idea as it stops the concrete from cracking which can happen with a large block of concrete. And it’s cheap. 

Edited November 2, 2019 by johninderby

[ollypenrice]

3 hours ago, johninderby said:

Fresh concrete isn’t that hard to drill. The concrete gets harder as it gets older. Try drilling 50 year old concrtete sometime. 🤬

I use my cordless SDS drill and it makes a huge difference over trying to use a standard drill even if it has hammer action. 

Adding fibres isn’t needed for strength in your case but a good idea as it stops the concrete from cracking which can happen with a large block of concrete. And it’s cheap. 

Although you're right, it does get harder to drill with age, you do get a better hole if it's close to its maximum strength, I find. And, yes, a hefty SDS hammer drill, even a budget brand one, is a godsend. Mine's a Grup (whoever they are!) but it's been fine over a good number of years in amateur use.

Olly

[johninderby]

Bought my Ryobi cordless SDS drill a few years ago. Will handle a decent sized drill bit unlike many cordless SDS drills. Already had Ryobi batteries and charger so made sense to stick with Ryobi.

Doesn’t get used a lot but but certainly a very useful tool to have around.

[Adam J]

On 01/11/2019 at 15:40, Adaaam75 said:

Hi guys,
Just a quickie, I've moved and am relocating my steel pier. So, would postcrete do a decent job for the footing of my steel pier in conjunction with rebar and 14mm threaded bolts? I'd make the hole big enough to cater for the size of the pier base and threads, I'm just purely asking if it will be strong enough as it is designed to hold concrete fence posts up with fence panels in the wind. The alternative is to mix concrete but if postcrete in the right quantity will do the job satisfactorily I'd choose that for convenience.

 

 

Thoughts please 🙂

Adaaam75

 

 

No I would not do that, its crumbly and cracks very easily while drying, horrble stuff really.

Edited November 2, 2019 by Adam J

[Adaaam75]

On 02/11/2019 at 09:59, WanderingEye said:

The reason I drilled and set bolts in with a special resin, is that it all came as a kit with my pier, as they are 16mm studs, if I were to set in the concrete, they would need to be bent, to stop them moving or turning in the concrete when bolted too, but if you have some studs long enough that can be bent, then yes, set them in the wet concrete, it would be easier I guess, I also already owned the mixing paddle for mixing the concrete, and a big heavy duty SDS drill for drilling the holes, if you don’t and can’t borrow them, then that would be extra cost hiring them...you won’t drill the concrete with any standard drill, I can assure you.. 😀👍

PS, I never added any fibres or rebar, not needed with a good strong 5-1 mix of ballast and cement...just make sure your block is big enough to have the bolts at least 100mm from the edge if drilling, if setting in, then that does not matter so much...

I need help!

I'm going to bend my threads!

So I'm happy with the concrete and ballast mix ratio, but I'm looking at how much I need and with the block measuring at 60cm X 60cm X 60cm I've used an online calculator stating I need roughly 375kg ballast to 3 bags of 25kg cement but nowhere sells ballast in weight! I've looked at bulk bags hoping they would be enough but the reviews at B&Q/Wickes on their ballast are poor saying they're full of waste and rubbish.

The smaller bags of ballast have no weight on them as it changes dramatically when we're and I have no idea where to get it from or how much I need. Any suggestions please.

 

[johninderby]

The typical bulk bag is 800kg to 1000kg.

When I had to pour a large concrete base found it was easier to just order 25kg bags from an online supplier. Also makes it easier to carry the bags round to where you will be using them rather than having to shovel stone into a wheelbarrow to move it. 

Edited November 3, 2019 by johninderby

[bottletopburly]

3 hours ago, johninderby said:

order 25kg bags from an online supplier. Also makes it easier to carry the bags round to where you will be using them rather than having to shovel stone into a wheelbarrow to move it. 

Plus 1 for that tip  , my tip just use a local builders merchant  work out how many bags and cement  needed and a few spare just in case you run short ,hire a electric mixer from a local hire shop cost is about £15 for a weekend they will drop it off and pickup ,i used rebar in the bottom of mine a bit overkill , make a wooden disc  to take   m10 or M12 threaded bar that will fit pier base holes ,double nut bar to disc ,make sure you bend threaded bar in on the end so it can't come out once set in concrete,  once concrete poured push threaded bar into wet cement  levelling as you go, once all set remove disc  you will see underside nuts incased in concrete you can use these to level base once bolted down if not sitting level by adjusting to suit  thats all i done .

  https://photos.app.goo.gl/1TimCVQde3zcS4mQ7

[WanderingEye]

4 hours ago, Adaaam75 said:

I need help!

I'm going to bend my threads!

So I'm happy with the concrete and ballast mix ratio, but I'm looking at how much I need and with the block measuring at 60cm X 60cm X 60cm I've used an online calculator stating I need roughly 375kg ballast to 3 bags of 25kg cement but nowhere sells ballast in weight! I've looked at bulk bags hoping they would be enough but the reviews at B&Q/Wickes on their ballast are poor saying they're full of waste and rubbish.

The smaller bags of ballast have no weight on them as it changes dramatically when we're and I have no idea where to get it from or how much I need. Any suggestions please.

 

My hole was a similar size 600 x 600 x 700 deep..

I ordered a half bulk bag (800kg) of ballast (£30) but only needed approx half of that which equates to approx 20 x 25kg bags and 4 x 25kg babes of cement, so your calculations are pretty much spot on...

The builder merchant said that a Half bulk bag of ballast is approx 40 x 25kg bags (1000kg) ...so A full bulk bag of ballast  is approx £2000 kg...

which is about right as a cubic meter of concrete is about 2500 Kg, and a bulk bag is a cubic yard, which is a bit smaller..

Edited November 3, 2019 by WanderingEye

[Adaaam75]

Guys all excellent tips. Will crack on and post results, thanks for solid adevice all round

[bottletopburly]

i set pier adapter up last to polaris by drilling and tapping  last ,rather than trying to set pier up to polaris all pre done ,if that makes sense .

[Adaaam75]

On 01/11/2019 at 16:15, johninderby said:

I would add fibres to the concrete mix as it reduces cracking and makes for a stronge base.

Fibres added to my mix, thanks for the tip John, now I just have to remain patient and wait long enough before I unfo the bolts and remove the template to mount my pier!

[Bukko]

You should only need a couple of days for the concrete to set enough to remove the template - providing you have not tightened the nuts so much that you need to lean on a big spanner to undo them of course !!

Fitting the pier, I would wait until the base turns white; depending on temperatures, should do so in a week or two. Until then, don't try and fit the pier, even if you have perfect skies..

Good luck,

Gordon.

[Adaaam75]

2 minutes ago, Bukko said:

You should only need a couple of days for the concrete to set enough to remove the template - providing you have not tightened the nuts so much that you need to lean on a big spanner to undo them of course !!

Fitting the pier, I would wait until the base turns white; depending on temperatures, should do so in a week or two. Until then, don't try and fit the pier, even if you have perfect skies..

Good luck,

Gordon.

Thanks Gordon.

I have a confession, the nuts are rather tight either side of the OSB template as the holes in the pier base for the 16mm threads base have been made with literally 1mm forgiveness (my fault when drawing the template for the pier!). So I had to ensure the threads would not move once they were in position. Either way, i have waited long enough for my pier to be installed (abandoned a nearly complete ROR Obs project when we moved )  so a few extra days won't hurt but I am keen and have spare days from next Tuesday onwards to continue the installation which is exactly a week since laying the cement. Hope fully my back stops hurting by then!

I just hope i can get the pier neatly onto the threads without taking it back to my brother in law for minor hole adjustments. It is powder coated so i'm hoping it will be fine.

I'm assuming the OSB board will just lift off and won't have bonded to cement?

I've not been a photo junky but will post some pictures once it's all set up.

[Bukko]

Its worth trying to get any shuttering and stuff out of the way before the concrete fully hardens. Easy way to separate the template is getting a second spanner on the lower nut to support it, then undo the top nut. Should be no problem now.

But if you think the OSB is in contact with the concrete, then it's unlikely you will get the second spanner onto a nut... How does the concrete look now? Turning grey/white yet?

Oh, everyone on SGL loves pictures so don't be shy haha.

Gordon.

[Adaaam75]

Thanks for all your advice guys. Here is the final result standing proud and waiting for a clear night to get started..... Pier courtesy of a very handy brother in law, cover is a BBQ cover for now as it's the same make and style that's protected my bike and another decent BBQ for years, you can work the scope out yourselves!

[WanderingEye]

What cover did you get..?

As I have had a big issues with condensation, under mine.. ☹️