Dom's workshop build

[MikeG.]

.........I am also looking into hiring some tools for preparation and the concrete pour:
- Concrete poker I can get for £32(+vat)
- Power float I can get for £80(+vat)
- 'Easy float' for £36(+vat).......

Poker......yes. You'll use it for less than 5 minutes, but it's worthwhile.

Power float......that's what I did for my workshop, and if I were being critical, I would say it possibly produces too smooth a finish. When pushing hard with a plane my feet can slip a little unless I have the right shoes on. If I had my time over again, I might have hand-floated it. Also, you have to wait until the concrete is precisely right, and that might mean 2 o'clock in the morning

Easy float.......too much skill involved unless you have done it before.

With your small base I would hand float. You work with a steel trowel, reaching in from the edges as far as you can, then carefully laying a board on the top of the concrete and kneeling on it to reach the middle of the slab. If you have a plastic float in your non-working hand you can use it to hold/ balance yourself as you go, resting on the concrete. Again, the critical thing is timing. Too early and you'll leave indentations in the surface of the concrete. Too late and you won't get it smooth. Just keep checking the concrete every half an hour to see how it is setting. Try the trowel..........if it raises water the concrete still isn't ready.

You do the floating after you have tamped the surface with a long straight-edge. You'll need wellies on, and you stand in the wet concrete, working backwards. Use both a tamping action (up and down) and a cutting action, where you go back and forth across the surface, cutting away the high points. Fill in low points from behind you as you go. As a beginner you'll need a straight piece of wood which is longer than the width of your base.

Pour it, tamp it, walk away.......clean up all your tools and boots at this point, using lots of water and a stiff brush. Go back regularly to check on the rate of setting, and judge when to start troweling up the surface. The following day, carefully spray the whole surface with water, and keep it constantly wet for a day or two. If you then start bricklaying, keep off the concrete. Work from the outside. Stack your bricks on the ground outside the concrete. Otherwise you'll likely generate powdering of the surface.

Now...get on with it!!

 

[DomD]

Now...get on with it!!

I want to get started but currently on holiday! Hopefully pour will happen next week and framing will begin the week after. I will buy some 2x6s to act as a tamping board and for hand floating.

Are cheap concrete/bricklaying tools worth it for this use case? I can't imagine I will be doing any more in a long time and don't know if I can justify £30+ for a trowel.

Also any recommendations for 'anti-alkali gloves"? Are washing up gloves acceptable?

 

[Woody2Shoes]

PS shouldn't be any over as a good pump operator should gauge when you are getting near the end of your pour and how much he has in his line and run pump empty to top up footing

I think this does depend on the type/design of pump - and the amount of additional pipework attached. My local supplier asks for - and uses - a "washout box" 2mx2mX200mm which usually gets about two-thirds-full of surplus concrete material and washing water from the pump. I also need to have on hand extra bags of dust (one per 20m of pipe) for grout to prime the pump. Cheers

Is a suitable 'washout box' just a ditch in the ground? The concrete supplier has said it will be 2-3 barrels from the augers and perhaps a little extra from too much concrete getting blown through.

I am also looking into hiring some tools for preparation and the concrete pour:
- Concrete poker I can get for £32(+vat)
- Power float I can get for £80(+vat)
- 'Easy float' for £36(+vat)

I am wondering if you need to first use a boom float then a power float or I could just hire the latter.
Thanks

I think Mike and others have already answered most of these these. Of course you can washout into a (your) ditch - but the liquid isn't great for tree roots etc. and the solids can be reused elsewhere, so it's your choice really.

I like gloves that are fully nitrile dipped and fabric lined e.g https://www.safetygloves.co.uk/22173.html and eye protection is well worth it too while on the subject of PPE. You could use kitchen gloves but they're very sweaty!

Cheers, W2S

 

[Woody2Shoes]

...and two years on its still fine....

adidat

Two years? Early days! I don't know what your subsoil's like in zummerzet (probably quite stony?). I guess it will last much longer without steel in it anyway!

 

[DomD]

I will get some of those gloves. I think I may dig a ditch and line it with dpm for the washout box.

Most earth has now been removed from ditches so I will begin to fill with mot 1 then sand.

Concrete delivery is booked for Wednesday so hopefully I can begin bricklaying on Friday!
Dom

 

[DomD]

Mot 1 down and compacted (with sledgehammer), sand blinding down.

 

[BigMonka]

I can’t add any technical sort of help, but just wanted to say that I love watching threads like this develop so thanks for going to effort of posting it all

 

[DomD]

If it were me doing it, I'd put down a sheet of DPM across the whole thing - wrapping the edge over your formwork and fixing it along the edge with battens. Two reasons for this:
1) the concrete will cure better, as the soil underneath won't suck out any moisture from it.
2) you'll save a bit of concrete (at £100+VAT or more per metre) from leaking out under the forms under the outer corners (I take the previous poster's word for the fact that if you follow his technique you won't 'lose' much but...especially if it's a 'pump mix').
Spending £20 on some plastic sheet and half an hour fixing it in place might save it's worth in concrete (there's a certain amount of waste with a pump anyway) and yield a better-cured slab.
Cheers, W2S

Forgot to ask this - will this not lead to water becoming trapped between the bottom of the concrete and the dpm?

 

[J-G]

Am I missing something?

You said on 12th July "Will be trimming down the posts;" but I see that many of the posts are still higher than the form-work so will interfere with the tamping once the concrete has been pumped.

 

[DomD]

Am I missing something?

You said on 12th July "Will be trimming down the posts;" but I see that many of the posts are still higher than the form-work so will interfere with the tamping once the concrete has been pumped.

Cutting now (only front and back)!

 

[Woody2Shoes]

If it were me doing it, I'd put down a sheet of DPM across the whole thing - wrapping the edge over your formwork and fixing it along the edge with battens. Two reasons for this:
1) the concrete will cure better, as the soil underneath won't suck out any moisture from it.
2) you'll save a bit of concrete (at £100+VAT or more per metre) from leaking out under the forms under the outer corners (I take the previous poster's word for the fact that if you follow his technique you won't 'lose' much but...especially if it's a 'pump mix').
Spending £20 on some plastic sheet and half an hour fixing it in place might save it's worth in concrete (there's a certain amount of waste with a pump anyway) and yield a better-cured slab.
Cheers, W2S

Forgot to ask this - will this not lead to water becoming trapped between the bottom of the concrete and the dpm?

If the plastic were not there, the underside of the concrete would be wet most of the time regardless. Concrete (that has no cracks - which of course, for all practical purposes, does not exist) is essentially impermeable.

Good luck tomorrow, I'm sure it will all go very smoothly (pun almost intended)!

 

[DomD]

I can’t add any technical sort of help, but just wanted to say that I love watching threads like this develop so thanks for going to effort of posting it all

Hopefully some quick progress from now on .

Dpm and mesh down, mesh stapled to shuttering.

 

[DomD]

If the plastic were not there, the underside of the concrete would be wet most of the time regardless. Concrete (that has no cracks - which of course, for all practical purposes, does not exist) is essentially impermeable.

Good luck tomorrow, I'm sure it will all go very smoothly (pun almost intended)!

Ah ok, I will just trim it down to the bottom of the visible slab after the fact then. Early start at 8 tommorow... I hope the extremely high temperatures (30 tommorow, 37 the next) don't speed up the drying too much.

 

[DomD]

Do I use the poker just on the thickened edges or over as much as the slab as I can?

 

[MusicMan]

I would consider having your electronic bench as a self-contained sealable bench, something like a fume cupboard - could even be an old fume cupboard, rather than a separate room or partitioned-off area. With a deep electronics bench you could have storage drawers/shelves at the back, simple ply or MDF would make the sides and top and carry the electric plugs for the station, and some storage space my be left on top.

Then in a couple of years when you decide it's in the wrong place, it's easier to move than a room!

Keith

 

[DomD]

This is my planned 'schedule' for tomorrow:
1) Pour concrete and move to fairly even
2) Use poker to compact concrete in trenches
3) Use wooden board to screed concrete
4) Use float to push larger rocks below surface
5) [after I can step on concrete leaving 1/4in impression] float concrete with weight on two boards

I can't believe this but I managed to forget to buy an edging trowel! Is that much of an issue?
Thanks

 

[DomD]

Also forgot about electrical supply...
Done now sketchily - I imagine this will collapse in and I may have to manually place it in the concrete.

 

[DomD]

Concrete poured and screeded - some imperfections but overall ok. Used poker in ditches. Need to float later today.

 

[Woody2Shoes]

Very exciting! Don't forget to cover the top (esp. in this weather!) so it cures properly and doesn't risk cracking (first 72 hours are critical). Cheers, W2S

 

[DomD]

Very exciting! Don't forget to cover the top (esp. in this weather!) so it cures properly and doesn't risk cracking (first 72 hours are critical). Cheers, W2S

Thanks for the reminder! Any ideas how long till I should float - I'm thinking a couple hours but don't want to miss the ideal time.