Can anyone do this sum because I have given up

[TheMustressMhor]

Okay - so we are putting concrete slabs on a small area of the garden.

This measures 12 ft x 8 ft.

The slabs we have chosen measure 450mm x 450 mm.

My brain has fallen out trying to work out how many slabs we will need.

Even the woman in the shop got three different answers and eventually sold us 36 slabs.

I think 36 slabs is wrong.

But the fact that I am incapable of working this out is driving me mad. My brain has fallen out and I appeal to anyone who has any sense to tell me how many slabs we need.

TIA

The full story about DH and the fried eggs is in

this thread

The word "tessellate" is derived from the Greek word "tesseres,"

which brings us almost back to Brexit.

you can't reuse slab pieces after they are cut

You can. I don't understand why so many posters are assuming you can't.

As you can see from lemonjumper's diagram, if you don't reuse the offcuts you will need 54 slabs and will throw a lot away.

At the other extreme, 45 assumes you can use all the offcuts and that there are no breakages.

I agree with B&Q that 50 is the right number to buy - the 45 you definitely need and another 5 to allow for breakages.

So - 50 it is, then.

And no, our plates do not have tessellated designs on them, to whoever asked.

Just food, usually.

TheMustressMhor There must be a correct answer, surely?

Have only read page one of thread but if you wait til 2301 hrs tonight it should all magically become clear as everything returns to feet and inches and be easy to fathom (that's 22ft)

I meant does the food tessellate on the plate, (maybe make everything square?) but it doesn’t matter

There must be a correct answer, surely?

I was naïve enough to think this.

The word 'slab' now looks really odd after I've read it so many times on this thread

There are a number of correct answers - but the question currently isn’t specific enough to know which one is right for you!

How are you planning to lay the tiles. Checkerboard or pavement? Do you feel confident in your ability to cut the tiles accurately, with no mistakes. How big a gap is the gap going to be? Will the tiles be laid up to a lawn or flowerbed\gravel boarder, or is the whole area to be tiled?

Lots of questions before you can get a definitive answer.

How are you planning to lay the tiles

I am planning on watching DH lay the tiles.

I shall sip sherry while he does it.

I got 44.

GeistohneGrenzen at last, a Brexit upside! A New Britannia Fathom will be worth more than triple an old EU fathom (which is 6 feet).

Well, I'm quite a basic soul.

I would draw one of the correct slabs on a bit of cardboard with the correct dimensions of that slab (or cut 50-60 paper one's out)

I'd then go outside and physically lay them on the ground and just count how many I'd needed.....

You would be looking at 45.

Converting units, the plot measures 3658 x 2439 mm.

That means it's 3658/450 = 7.9 slabs long. Round that up to 8 slabs.

And 2439 / 5.42 slabs wide.

Now you could round the width up to 5.5, assuming you'll split slabs into two pieces slightly less than half and a little leftover bit. So that would be 8 5.5 = 44 slabs*.

Or if you need a whole new slab for each 0.42 piece, you'll need to round the width up to 6 slabs, making the total 48.

Of course if you were to lay the tiles vertically to create a weird elevated patio the answer would be different again

There must be a correct answer, surely?

Not to the original question. As mentioned by PPs, there are too many variables, e.g:

• how big will the gaps be between slabs
• are there rounded edges meaning you cannot use the rest of a tile once you have cut it?
• will the tiles break when cutting, again meaning you need a whole tile for each cut part?
• is the original area the area to be paved, or does it also include the woodchip?

Scrap that, I made a calculation error, d'oh! It's actually 8.13 slabs long, so you'd want more slabs!

But considering you'll have a bit of the gap between the slabs, you might be OK with 44 slabs after all. Or use bricks to fill in the gap at the end rather than having to cut little bits of slab.

So you need a grid of 9x6 = 54.

This is what I got too, and how I got it.

Sorry, I don't have time to do the calculations but may I make a suggestion? I would get a piece of graph paper (or draw out a grid) and draw the layout. For it to look good, you want the centre of the patio to be the centre of a slab or the centre of 4 slabs (so the grout between the 4 corners). You will then probably have partial slabs at the edges. You might have to fiddle things to make it look good if you end up with a tiny part slab on the edges. Count up the whole slabs then calculate how many whole slabs you need to get the partial tiles (you might get 2 or more from a whole slab, depending on the size).

I think you are getting different answers because some people are counting each partial slab as a whole slab without taking into account you can cut them into several partial slabs or using different layouts eg starting in a corner versus starting in the middle.

42/43 slabs needed, probably 44 allowing for tiny gaps. Area is 12x8=96 sq ft, your slabs at 450mm sq equate to just under 18 inches or 1.5 ft so each will cover just under 2.25 of your 96 sq ft. Your 12 ft side will take 8 slabs in a row but your 8ft side isn't a neat multiple so it will take 5 slabs and leave a 6 inch gap that will need either to be pieced with cut slabs from 2 extra whole ones or filled in with something else like gravel. You could have 3 inches of gravel at either end. Either way you need 40 slabs or 42 if you cut them.

He didn't buy quite enough. 😕

It isn't just maths, it's practicality. Mixing metric and imperial is your problem!

Oh, ignore the numbers at the beginning and take the ones at the end. That wasn't helpful at all, sorry.

Each slab is 1.5 ft square what's the problem?

12 /1.5 =8
8 / 1.5 = (6 rounded up)

8x6=48

You need to put it all in same measurements. I converted everything to cm and got 44.28= so 45 slabs needed.