Formwork to slab on ground - YouTube

So in this video we back out on the

Site from the marking up video and what I'm going to show you this time is how we go about

taking our setting out and then creating formwork

for a slab on ground

This is a slab on ground

as

You can see the main feature of this slab is that it has a step or a rebate

So what happens when we construct the the house

Our brick veneer goes on the lower edge of this step and our timber frame sits up on the top of this step

that allows us to put our flashing in and

Form weep holes in our Brickwork

so we can drain any moisture

any water that gets behind our brickwork can come out and not make any contact with our timber frame, so that's what we

need to achieve, so

Remember from the marking out video. We got all the our string lines in place

Look something like that, and now we can

Start to create our formwork so the first thing we need to do pick a side any side and pumb down

Your main points in fact what I would do is I would go around the whole site and I would

Transfer these marks down onto the ground with

Some spray paint or a bit of Lime or scratch mark on the ground whatever you've got available, the plumb, or use a

Spirit level or a plumb line a transfer these marks onto the ground

Then we can go around and actually lay our timber boards in place

or our Edge boards

Now because this is formwork. We don't want to necessarily cut these timbers to exact length

So where possible we want to actually extend these past our points

This one is actually cut tight or cut in between

But you'll see a lot of the other ones in the video will be extended past

So where you can don't cut formwork to length because you want to be able to reuse it

Okay, I'll get rid of the string lines here shortly, so what we have to do is we put these

pegs in to hold our Edge board in place

This is one method of supporting the Edge boards. I'll show you another one shortly

the disadvantage of this method is that

When you drive these pegs in if they hit a rock in the ground or you got particularly hard ground

It's very hard to keep that Edgeboard exactly where you want it to be

so there is a way of getting around that I'll show you in a second, so

first thing we have to do support our Edge boards, at both ends

And then we need to get it straight, so the best way to do that

Grab a block of timber we actually need three all the same same thickness one block goes on this end

now the block block goes down on the other end and

We take a stringline and then we wrap it around the blocks

To a nail here, take take it around the block up to the other end

once again a nail tie it off tight, and then we can put a block in the center and

if the block slips between the Edge board and the string line

Without any gap, then the Edge board is straight so we can put a peg

behind that

And we just repeat that process as many times as we need to to get our pegs in now

Depending on the Edge of this the thickness of this edge board

You're probably going to want a support Roughly every metre

Behind your Edgeboard it depends on how thick it is

Whether it's going to bow or not under the weight of concrete, so that's a decision you have to make yourself, but roughly

Every metre, you'll need a support

Okay, so there's our first Edgeboard in

Now we're going to swing around and do our next one so as I said before

You can either put your stringlines back up which is a bit of a pain or you can already have this mark transferred down

Put in another Edgeboard now in this case

one Edge board wasn't going to be long enough so we had to join it with a cleat and

The process is the same

Except this time to support the Edge board. I'm going to use two pegs and

a ledger

so this just means I can drive these pegs in anywhere pretty much well

they don't have to touch the edge board and then I can slide this the ledger in till it touches the back of

The Edgeboard now the only thing you need to be careful of is that this Edge board is sorry this ledger is level

So at the moment that looks like you're using a lot more timber

Than what you used during using this method which you are, but you'll see when we actually form the rebate

It'll become a little bit more efficient. So one support at that end

support at the other end

stringline in the face again with our blocks and we straighten out the

straighten out the formwork

put a support in the middle

Keep checking up with your block and put all your supports in

That's the process and you just have to work your way around

the entire site

until you get that done, so

that's the first layer or the bottom step of our rebate, so now we need to do that here at the top step

so what we're going to use is another peg and a ledger and

that peg and ledger the pegs this can be back whatever length your ledges are and

We need to sit this

top of this ledger

150mm

so if you measure 150mm from the back of

the this Edge board

To the face of your ledger [that] will mean [that] it will be 150 Ml from the face of this Edge board

to the face of the [Edge] bulb we're going to put on here and

We just do that all the way along

So that's one method there are brackets that you can purchase or you could have made

that this simply sits over your bottom Edge board and

Then you screw them on

To the bottom of the Edge board the bottom side

you then sit your

Second Edge board on here, and they screw into the back of that, so that does the same job a little bit quicker then

using the Timber Edge boards

but if you're going to um if you're not going to do it very often then may not want to go the expense of

purchasing these brackets

So we'll go back to the timber method. So that's that Edge done. Let's see on the other side where we use the different method

Now we've already had that second peg in place

so we just had to put the ledger in make sure it's overhanging the 150mm and

That's that's complete so realistically with this system only extra timber. We're using is that bottom ledger over this system

So it's a little bit more efficient than it used to look I

Personally think this is a better way of getting nice straight Edgeboards using this method. Can't get your edgeboards of straight

again, we have to go around the entire site and do that and

Then once that's done. We go around and put in our top Edge board and

We've got our rebate formed

Can have a little bit of look around

Okay, so once we've got our edgeboards in and all their formwork done we then have to think about filling up

the center of the Field of the slab so one of the methods is quite commonly used nowadays is a

styrofoam

Pod

In Australia they call them waffle pods

Because this you know the inside of your house is not going to get heavy traffic. Just furniture and people

You really don't need to have I said that's 200-300mm thick so what they do is

They put these pods in and that just means that for the majority of the slab

The thickness of the Concrete is only about 100mm

Which is heaps if you're going to have an area in your house that was going to take heavy loads like possibly a garage

Or somewhere

were your going to have a pool table or, your know, a spa or water bed that might have point loads on your floor

You would have to

Consider that in your design and possibly remove the waffle pods in those areas, but that's up to your structural engineer to work out

So the waffle pods go in now instead of using waffle pods. You could use dirt or sorry controlled fill and

Sand but nowadays waffle pods are the common thing

Once your waffle Pods are in

You place in Trench mesh in the lower half

to

reinforce the bottom of these beams that will be formed by waffle Pods and

Then on top of that on the top of the waffle pods you put in your fabric reinforcement or the mesh

Making sure all the reinforcements to your slab

And of course once that's all done. It's been inspected and

you pour the concrete

Take and see now a little step here has been formed in the slab

and

There's our slab formed now once you pour the slab generally you should take about seven days

before you pull this formwork off a

Lot of contractors and concrete and professional concreters will do it on the same day

But the risk is that if someone or something was to run along one of these edges then the concrete could possibly fall off

so you really want to live it seven days take seven days to to get some strength about it and

Then realistically all it takes 28 days to reach its designed strength

There we go. There is our slab on ground with our rebate all formed up

Ready for our frames and our bricklayer