Building a Block Workshop - ADVICE NEEDED!

[Iceverge]

A sturdy metal rake is the top tool for concrete, forget shovelling. Wellies and gloves too, it's nasty on one's skin. 

 

I wouldn't worry about having it a bit wetter for what you're doing, it's not a skyscraper, the slight reduction in strength will be more than compensated by having it a bit more workable. Tamping it down with the rake will work fine to remove air at the scale you're at if you want to avoid a poker. However a couple of pieces of rebar are cheap and will make it infinitely stronger. Keep them about 50mm from the bottom of the trench, supported on chunks of brick/rubble. If you have it I'd be tempted to use lengths of rebar instead of timber pegs. You can just leave them in the concrete when you're done. The string will just get in the way I reckon. 

 

Here is my technique for one man concrete. 

 

 

Mates and concrete goes the same way everytime I've seen it. All first timers start really enthusiastic until about 10 minutes in. Then they start leaning on tools and grumbling about the heavyness of the work. Self scheduled breaks start appearing, totally unaware of the time limited nature of the job. The couple of seasoned concrete workers meanwhile be pushing on, steely eyed and sweating. 

 

Have a power washer setup if you have one. If not a couple of large tubs and stiff brushes. The job isn't finished until everything is cleaned down. 

 

Best of luck! 

 

 

[saveasteading]

Deeper is fine, and extra concrete to get back up to a standard level is also sensible.

In the absence of a vibrating poker, do still compact the concrete by poking vigourously from top to bottom, using a 2 x 2 or similar. You won't  see it but a lot of air will come out, the concrete be better mixed, and the concrete become denser as intended.

19 hours ago, TonyT said:

easier with a few bodies

Yes. That is a lot to shift and level on your own esp if the weather isn't great.

[stunotch]

I've now got the foundations poured and just looking at setting out the first course. 
I plan to lay the first course of blocks on their sides and then a second course normally. I'll then look at putting the DPC & insulation down before pouring the floor. I've got 75mm insulation and was thinking 150mm for the concrete floor, sound about right? 

 

Questions though! How do I manage where the door is going? Do I just cut a concrete block so it is level with my finished floor level where the opening will be? The height of the second course will obviously be too high. 

 Do I cut this opening before I lay the floor? 

 

 

 

Edited November 1, 2022 by stunotch

[Chanmenie]

Bit late now, but why did you fill the trenches instead of leaving them a course below ?

If you now add 75mm insulation and 150mm concrete your finished floor will be 225mm above ground level which will impact your permitted ridge height 

 

[stunotch]

7 minutes ago, Chanmenie said:

Bit late now, but why did you fill the trenches instead of leaving them a course below ?

If you now add 75mm insulation and 150mm concrete your finished floor will be 225mm above ground level which will impact your permitted ridge height 

 

Thanks,
I managed to get the groundsmen from the Taylor Wimpey development behind my house to pour the concrete over the wall for me, I originally planned to have it lower, but they convinced me that it was better to bring it up to that level to start the first course. The floor will still be at the same level because that is the level the ground is at in the centre, where I will be pouring the floor. It was always going to be 225mm higher. 

[stunotch]

I cant remember why they said to have it poured to the top now, but it did make sense at the time and they should know what they are doing having built nearly 300 houses behind! But I am also now thinking that the block on its side will be visible? Hmmmm.... 

 

Should I maybe not lay the first block on its side?? 

Edited November 1, 2022 by stunotch

[saveasteading]

Firstly, is the footing completely level, not simply to the top of the trench?

You will bury the bottom block, anc as an amateur brickayer this isn't a bad idea anyway for getting your line and level right.

Why 150mm concrete slab? That is very thick. You can run forklifts on that.

Nobody ever fell through a 100 slab, or 75 come to that.

 

The norm would be to build the wall to slab level, pour your slab, then start again. 

[stunotch]

11 minutes ago, saveasteading said:

Firstly, is the footing completely level, not simply to the top of the trench?

You will bury the bottom block, anc as an amateur brickayer this isn't a bad idea anyway for getting your line and level right.

Why 150mm concrete slab? That is very thick. You can run forklifts on that.

Nobody ever fell through a 100 slab, or 75 come to that.

 

The norm would be to build the wall to slab level, pour your slab, then start again. 

Hi, 
The footings are level, they used their posh laser level which was a lot better than mine! 
I've got the 75mm insulation slabs, and Taylor Wimpey guys suggested 150mm concrete floor? Do you think that is too thick then? 

If I was to build the 1st course to slab level, then that would be higher than needed though? (The height of a block / 215mm, if I don't lay the first block on its side?) 

[markc]

We have 150mm concrete in our workshops and regularly put down 20tonne+ point loads

[Chanmenie]

1 hour ago, stunotch said:

Hi, 
The footings are level, they used their posh laser level which was a lot better than mine! 
I've got the 75mm insulation slabs, and Taylor Wimpey guys suggested 150mm concrete floor? Do you think that is too thick then? 

If I was to build the 1st course to slab level, then that would be higher than needed though? (The height of a block / 215mm, if I don't lay the first block on its side?) 

Are you parking heavy vehicles in it ? If not then 100mm will be plenty 

especially if you have compacted hardcore base 

[stunotch]

Ok thanks, maybe no need for 150mm. 

 

Should I start the first course upright then, and cut the door in?

[saveasteading]

A subcontractor to TW, supplying concrete over a wall, is not my choice for advice.

Literally off the back of a lorry, but i won't speculate further.

 

For 16m2 you are only using 2m3, and reducing to 100mm will save you 1/2m2 but add labour.

 

But just bear in mind that 100mm is plenty if you need to adapt as you go.

[Chanmenie]

31 minutes ago, stunotch said:

Ok thanks, maybe no need for 150mm. 

 

Should I start the first course upright then, and cut the door in?

Yeah that would work, for the doorway you can cut the blocks down or use coursing bricks 

[Canski]

Why not cut the bottom block in half down its length so you have 2 x 440 mm x 112 mm x 100 mm blocks and lay them flat leaving the cut edge into the inside. Your total height of the wall would then be the same at 335 mm (110 + 225 mm ) then cut a block up to the top of your finished concrete height where the doors are.

[stunotch]

14 minutes ago, Canski said:

Why not cut the bottom block in half down its length so you have 2 x 440 mm x 112 mm x 100 mm blocks and lay them flat leaving the cut edge into the inside. Your total height of the wall would then be the same at 335 mm (110 + 225 mm ) then cut a block up to the top of your finished concrete height where the doors are.

Hi, thanks but i'm not sure I understand what you mean? 
Cutting a block in half, is this for underneath where the door will go? 

 

[Canski]

18 minutes ago, stunotch said:

Hi, thanks but i'm not sure I understand what you mean? 
Cutting a block in half, is this for underneath where the door will go? 

 

No ! for the complete first course. It will stop the bottom course being visible and sticking out as you mentioned earlier. What height is your door cill going to be from the top of your concrete foundation ?

[stunotch]

21 hours ago, Canski said:

No ! for the complete first course. It will stop the bottom course being visible and sticking out as you mentioned earlier. What height is your door cill going to be from the top of your concrete foundation ?

I See, Seems like a lot of block cutting though. The door cill will be level with the concrete floor, is that not correct? 

[saveasteading]

Flat blocks as the first course isn't going to cost you a lot.  Cutting woukd be a chore. Just be careful when filling and compacting against and over them.

[stunotch]

3 minutes ago, saveasteading said:

Flat blocks as the first course isn't going to cost you a lot.  Cutting woukd be a chore. Just be careful when filling and compacting against and over them.

Would it matter if I lay the first course of blocks flat, but then start building blocks on top of them but on the edge so they line up? 

[saveasteading]

As your picture? That is what I assumed we were talking about, and am OK with if you are careful in backfilling.

Not for a house perhaps but fine for a shed.

[stunotch]

1 hour ago, saveasteading said:

As your picture? That is what I assumed we were talking about, and am OK with if you are careful in backfilling.

Not for a house perhaps but fine for a shed.

I just realised that this still isnt going to work, I need the first course to be around 170mm so I can cast the floor to that level, then continue building up after that. 
I wonder if I could use 140mm blocks on their sides, would then mean 75mm insulation + 65mm concrete floor thickness ... maybe too thin though. 

Not sure what the best way to go is now... 

Edited November 2, 2022 by stunotch

[Iceverge]

Normally as said above they foundations would be left a little lower to give you a few courses of blocks to take any imperfections out of the foundations. 

 

 

Not to worry if your foundations are pretty level however, just use a good thick bed of mortar and lay your 100mm blocks on edge to begin with. 

This will give you ~ 225mm to play with for you floor. 

 

Some sand binding to avoid puncturing the DPM. 

DPM. 

Insulation. 

Concrete. 

 

I suspect the reason your 150mm floor depth came up was it was handily 75mm insulation + 150mm insulation makes 225mm.  I would buy more insulation and reduce the concrete to 75mm-125mm .  

 

 

 

 

 

[Iceverge]

Best practice would be to use some perimeter insulation as shown above. 

 

If you get another layer of insulation, you could put the DPM between the layers to avoid the need for sand binding. 

 

You'll need to tape the joints in the boards or lay a thin plastic sheet on top of the boards too before you pour the concrete to avoid them floating/concrete going between the boards. 

[stunotch]

59 minutes ago, Iceverge said:

Normally as said above they foundations would be left a little lower to give you a few courses of blocks to take any imperfections out of the foundations. 

 

 

Not to worry if your foundations are pretty level however, just use a good thick bed of mortar and lay your 100mm blocks on edge to begin with. 

This will give you ~ 225mm to play with for you floor. 

 

Some sand binding to avoid puncturing the DPM. 

DPM. 

Insulation. 

Concrete. 

 

I suspect the reason your 150mm floor depth came up was it was handily 75mm insulation + 150mm insulation makes 225mm.  I would buy more insulation and reduce the concrete to 75mm-125mm .  

 

 

 

 

 

Hi, and thanks for your help. 
If I use a block on edge at 225mm that would mean quite a step up on the door way from the ground level. I was trying to avoid that ideally, but maybe a bit stuck now as the concrete got poured to the top. 

 

[Canski]

2 hours ago, saveasteading said:

Flat blocks as the first course isn't going to cost you a lot.  Cutting woukd be a chore. Just be careful when filling and compacting against and over them.

My labourer can cut a pack in an hour with a block splitter but I’m guessing you don’t have one to hand.