Laying a concrete pad

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raytaylor

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#257254 22-Sep-2019 19:49

Hi Guys

I need to make a small concrete pad for a garden shed.

I use the Easy Mix 25kg sacks from Mitre10 quite a bit at work and am quite happy mixing them and pouring it.

But my question is how to make the surface smooth? The easy mix concrete comes with small stones in it but i dont want to have them on the surface of the pad.

I am not even sure if thats the right concrete to use. I dont really want to buy the ingredients individually - would prefer pre-packaged if possible.

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nickb800

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#2322878 22-Sep-2019 20:00

That concrete is fine, to finish you need to:
1) Screed - scrape off excess concrete to create a flat surface e.g. with a 4x2 guided by your boxing
2) Float - run a float over the surface, which brings liquid and fines to the top, giving you the smooth surface you want

tukapa1

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#2323059 23-Sep-2019 06:50

raytaylor:

Hi Guys

I need to make a small concrete pad for a garden shed.

I use the Easy Mix 25kg sacks from Mitre10 quite a bit at work and am quite happy mixing them and pouring it.

But my question is how to make the surface smooth? The easy mix concrete comes with small stones in it but i dont want to have them on the surface of the pad.

I am not even sure if thats the right concrete to use. I dont really want to buy the ingredients individually - would prefer pre-packaged if possible.

How big is the pad you're pouring?

You may find you need to take a second mortgage using the easy mix 25kg bags - they don't go far.

If you don't know anybody with a float you may be able to hire one for finishing - it will make all the difference.

neb

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#2323063 23-Sep-2019 06:54

nickb800: That concrete is fine, to finish you need to:
1) Screed - scrape off excess concrete to create a flat surface e.g. with a 4x2 guided by your boxing
2) Float - run a float over the surface, which brings liquid and fines to the top, giving you the smooth surface you want

+1 for all of that, with one addendum: Run a concrete edger around the sides of the pad where it meets the formwork, otherwise you'll end up with a jagged edge on the concrete later. For that, wait until the concrete has started to harden, it shouldn't be runny any more when you edge it.

driller2000

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#2323107 23-Sep-2019 07:17

i would order in the quantity you need as readymix - i was surprised how cheap it was when we did ours and it saves a lot of the work...

hio77

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#2323121 23-Sep-2019 07:44

nickb800: That concrete is fine, to finish you need to:
1) Screed - scrape off excess concrete to create a flat surface e.g. with a 4x2 guided by your boxing
2) Float - run a float over the surface, which brings liquid and fines to the top, giving you the smooth surface you want

Just make sure the 4x2 you use to scrape is actually straight...

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Dingbatt

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#2323126 23-Sep-2019 08:07

It may sound a bit naff, but both Mitre10 and Bunnings have excellent YouTube videos on just this topic.

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blackjack17

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#2323147 23-Sep-2019 08:45

You are also going to have to prepare the base.

Basically this is what you are going to have to do.

Make sure your site is flat, if your soil is firm lay a layer of gap 7 and compact (with a compactor). If it isn't firm you will want to put a layer of gap 20 first.
I would then put in a moisture barrier which is essentially a layer of plastic with the joins taped. It is only a shed but for the sake of a few dollars you might as well put it in, you can't retroactively put one in.
Build your external frame work with timber with the stakes on the outside.
Calculate how much concrete you will need 2m by 3m shed you will want 75mm-100mm thick concrete so 2x3x.1= 0.6m3 (if you use the 20kg bags you will need about 65 bags (around $500 worth at bunnings)
Hire a concrete mixed and get some builders mix and cement.
Mix according to directions and pour
Level off with a flat piece of timber.
Trowel it to bring the cement and water to the surface.
Keep surface moist for a couple of days to cure.

If this is your first attempt at working with concrete be prepared for a rather rough finish on the concrete.

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#2323152 23-Sep-2019 08:50

tukapa1:
You may find you need to take a second mortgage using the easy mix 25kg bags - they don't go far.

Maybe Ray has been buying 1 extra for every work job for the last 5 years. Hope they haven't gone solid.

As an example of doing it the hard way there's a YT video by an Auckland carpenter of using 15 x 40kg bags for 1 house pile. The queue for ready mix in Akl must be really long.

raytaylor

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#2323579 23-Sep-2019 21:59

Yeah cost isnt an issue when it comes to bags since i reckon I can do it with 32x 25kg bags. I can use my work ATV.

I helicoptered 8 tonnes concrete into a site for work last year but we werent too concerned about how smooth it looked. It was more just a matter of dumping it in the hole which is typically all we care about for most of my concreting jobs.

This is a personal job for a friends elderly father who doesn't want to leave his cottage and move to town so I cant rent a helicopter on the work credit card for this one. Also a concrete truck cant get anywhere near the site as the property only has a 4WD driveway so the 25kg bags are easier to transport.

So basically what your telling me is the easy mix is the correct stuff to use, but i just need to trowel it to make the stones drop and the cement rise for a smooth surface. Easy to do with a concrete vibrator i would assume.

- Trowel & Vibrate, bring cement to the surface, stones drop down
- Use a Float to mop it smooth

Thanks, I appreciate your help

:-)

Ray Taylor

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hio77

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#2323583 23-Sep-2019 22:14

dammit ray! ear warning please!!

get past the loud noise and my eyes burn! glad you got a better camera now... i've gotta go visit aliexpress....

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nickb800

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#2323631 24-Sep-2019 06:21

You don't need a concrete vibrator, it's in the action that you trowel with. There's a real skill to using a concrete vibrator - if you over vibrate your can push the large particles too far down and create a weak top layer of only fines

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neb

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#2323669 24-Sep-2019 08:01

blackjack17:
Basically this is what you are going to have to do.

That's a pretty pricey way to go about it. This tutorial video shows how to do it much more economically if budget is a problem.