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Putting down a concrete slab, what timbers to use?

Silverdream

I'm putting down a slab of concrete 20 meters X 5 meters and 100mm deep. I'd like to have it level and straight so am wondering what would be the best timbers for this, I was in my local hardware store and the guy didn't seem to know. I looked out in their yard and they had 16ft 4X2 timbers but they don't seem very straight.

Is there any other modern system that is being used today instead of timbers for the casing?

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lmk123

4x2’s would Be fine, anything bigger would be a waste of money, get a few lengths of 10 / 12mm bar and cut them up maybe about 300mm long, drive them in along the 4x2’s to keep them straight, drive a 3 inch nail at both sides of the bar and bend the last inch of each nail around the back of the bar and she won’t budge. Go to the hardware with a trailer if you can and pick out the straightest of the lengths yourself

K.G.

We nearly always use 6x3 s.they need less pinning and hold straight better.

mickdw

Ya 6 x 3 for speed and straightness but not really economical for a one off use. 4 x 2 will do the job but they will bend in all directions so you need to be super careful in supporting them.

GrasstoMilk

what are you using the slab for ? 100mm is quite thin , it will crack if the base isn’t good

If you could get your hands in the metal screeds you’d be far better off, they lock in together and you can set there height very easily, a local shuttering place might have them to hire out

Dunedin

if you can let in a bit of dryer mix around the timbers before you wet it up, it’s a good job too.

Silverdream

https://www.boards.ie/discussion/comment/122155601#Comment_122155601

https://www.boards.ie/discussion/comment/122154902#Comment_122154902

Its down on top of sheet rock so it wont be going anywhere, its for storing straw and a few bits of machinery, I've a kit shed ready to put ontop of the slab.

I was thinking of using 4X3 they might be a bit easier to hold, never seen the metal screeds but must check them out first. I dont fancy trying to get too many pins down into the rock to hold the timbers but they'll need a few.

mickdw

You will need a 6 inch slab if it's for a shed.

4 inch is liable to crack and break away at pressure points even if it is down on a slab of rock.

grass10

https://www.boards.ie/discussion/comment/122155984#Comment_122155984

If its on rock you need to put fill material over the rock otherwise the slab will crack anything less than 6 inches of concrete is a waste of money you also need a hammer action drill to drill bars down to support the timber have you considered employing a contractor to do it he won't have to buy any materials for the job and should only cost in total a few hundred euro to put down timber and pour the concrete

lmk123

https://www.boards.ie/discussion/comment/122156222#Comment_122156222

this is all 100% correct. You’ll be left with a pile of cracked broken up concrete if putting 100mm straight onto rock. Complete waste of time and money. You’d be as well off tipping a few loads of gravel for the floor of the shed and pouring pads for the columns.

K.G.

https://www.boards.ie/discussion/comment/122155984#Comment_122155984

Are the purlin s galvanised or are they 6 x3 s.if 6x3 s treat them use for the concrete and stick them up on the roof then.thats what we always do.

Silverdream

https://www.boards.ie/discussion/comment/122156222#Comment_122156222

I have put about 4 inches 1/2 inch down gravel it's not directly on the rock. I tried a few contractors but all I'm getting is broken promisses to call some evening, they are all mad busy.

I'll go over the 4 inches, thats the minimum it'll be at least 5 inches and 8 inchs where the shed uprights will go.

Anyone use those concrete placers, I've been told they are much easier to use than shovels?

Water John

The hoe is much handier. Use shovel to top up and move material around the tampering stick.

Water John

tamping😯

grass10

Farm building concrete lads are in general very quite this year as low profit made by farmers last year and the same this year means not much work going on but you have the same usual lads letting on they are busy I'd recommend you talk to a long established contractor as he may have to bring a machine to level out the ground properly and give you an even 5 to 6 inch slab it'll work out far cheaper for you at the end of the job

Silverdream

Limited number of lads available west Clare, you'd be surprised how few there are when you go looking for a builder as they're all tied up with housing or left the building all together. I've located one man who will put down the screeds and give me a hand with the Concrete, he's supposed to be retired with the last 5 years!!

Another question is how many meters of concrete do they put on a lorry now days, I remmber back in the day some of the lorries were doing 9 meters but did I read someplace that they are not allowed to bring that much anymore?

cjpm

9 is no issue with a 5 axle truck.

The articulated ones have 6 axles and can take 10m

green daries

https://www.boards.ie/discussion/comment/122158101#Comment_122158101

General run is 7 on the ordinary truck

Silverdream

I got a quote of 135 euro per meter inc vat for 25N 20 concrete (full lorry load), is that a bit dear?

grass10

https://www.boards.ie/discussion/comment/122161423#Comment_122161423

25 Newton is very weak their is not much cement in that you won't have a great finish 30 Newton is even weak your surface won't last even where their is no effluent on it I am not sure whether the price is dear or not

have2flushtwice

https://www.boards.ie/discussion/comment/122158101#Comment_122158101

I got 11 into a lorry, docket said 9 in case he was stopped by rsa.

Omallep2

I was quoted 140 in Galway a few weeks back for 35N. Thought it good value

green daries

https://www.boards.ie/discussion/comment/122161615#Comment_122161615

Half the yards and houses in the country are 25n this craic of a ball more cement for no reason is just madness

grass10

https://www.boards.ie/discussion/comment/122163022#Comment_122163022

Newton in concrete is the 28 day crushing strength lads don't understand that their are many ways of ensuring their concrete passes a 28 day test their is no such thing as a standard way of mixing concrete for quarries but in a 25 n mix out of a limestone quarry their is not much cement but when you look for 30 or 35 their is substancilly more cement most of the time their is no comparison

green daries

https://www.boards.ie/discussion/comment/122163225#Comment_122163225

Grand job whatever you like yourself but it's complete overkill ... end of story. I'm well aware about concrete and all that goes with it also.

V6400

https://www.boards.ie/discussion/comment/122162760#Comment_122162760

might be cheaper than some places but considering that would have been mid 70s a few years ago I wouldn’t call it value!

green daries

https://www.boards.ie/discussion/comment/122164440#Comment_122164440

It's unreal the increase in building costs and materials.

50HX

https://www.boards.ie/discussion/comment/122167698#Comment_122167698

Yeah not sustainable & the yearly carbon tax is just goin to keep it climbing

Silverdream

https://www.boards.ie/discussion/comment/122163022#Comment_122163022

I always thought 25N 20 was a strong concrete as the 20 mm chip makes the concrete a lot stronger. But it doesn't make for a nice finish, you won't be using that stuff for footpaths as it just doesn't have the "fat " in it.

Bought one of these too, I can wait to try it out, I heard so many ones praising them.

lmk123

https://www.boards.ie/discussion/comment/122181663#Comment_122181663

footpaths should be a 10mm chip with extra sand, roadstone are now charging extra for both the b****rds. Screw the laser receiver onto the placer it’ll save someone else going around telling you to go up and down, you can check yourself as you go. Also I’d go I’d go stronger than 25N if I were you, it’ll cost a thing of nothing extra for the amount of concrete you’re using.

green daries

https://www.boards.ie/discussion/comment/122181663#Comment_122181663

You get a 10 mm chip for footpaths easier finished loads of fat in it

You'll be delighted with the concrete leveler great tool