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

So as a previous poster pointed out you should allow a 10mm gap normally so should be dividing by 460mm so i make that 7.95 slabs long side. You could cut the end ones slightly or use a 7mm gap to avoid this.

On the short side this gives 5.3 slabs so you will need 8 thirds. As such i think youll end up using 43 slabs

Sounds like you have enough spares if a few cuts go wrong.

This is the funniest thread I've read in ages! . Sorry @TheMustressMhor

You need 45 slabs...each slab 1.5ft..so 8slabs × 5slabs..

12ft = 3658mm
8 slabs @ 450mm = 3600mm
3658mm - 3600mm = 58mm
58mm / 7 = 8mm joints between slabs

8ft = 2438mm
5 slabs @ 450mm = 2250mm
2438mm - 2250mm = 188mm
6 x 8mm joints (to match rows going the other direction) = 188mm - 48mm
188mm - 48mm = 140mm
The 140mm is going to be the width of the pieces at the edge, and you will need 8 since your rows are 8 slabs long in the other direction. You can get 3no 450mm x 140mm strips from 1 slab, so 8 / 3 = 2.7 which means you need 3 slabs to create the last row.

So it's 8 rows of 5, plus 3 slabs to cut down to strips to fill the last row. It is also advisable to factor in an additional 10% for wastage, so 47 or 48 slabs altogether.

I would say though, the last row being little strips might look a bit shit and they will potentially be prone to lifting, especially if they are at a free edge. Worth adjusting the area to allow for whole slabs if that's a possibility, or maybe having cuts at each end so you avoid narrow slivers at just one side.

I dont understand why people dont understand the difference between a square area and a rectangular area. Also most are missing out that their is a gap between each slab.

You will need 8 slabs along the length because their is gaps between each slab. You will need 5 1/2 slabs along the width (or 6 if unable to cut).

So you need 44 (or 48 if no cutting) plus amount for breakage. So between 44-50 is the right number of slabs you should get, depending on how good you are at cutting them. If you were really expert at cutting and had zero breakage you might even get it down to 43.

FFS

I am going to go mad soon.

So between 44-50 is the right number of slabs you should get, depending on how good you are at cutting them

Ha ha ha ha ha ha

That is DH's favourite answer so far.

Any advance on "between 44 - 50 " slabs?

54

Oy Desdemona.

Less of the insults, you cheeky cow.

It's not a proper garden - just an area which has no topsoil. It's already a patio but it has been done really badly.

We want to improve it cosmetically. We have loads of pot plants out there.

Not that it's any of your business.

Have you considered gravel?
This has to be the best thread I've read in a while; I suggest every maths teacher here sets this as homework next week...

Its not just a maths problem, it really depends on how skill-full you are cutting the slabs, exactly what shape the garden is and how much of a gap you leave between each slab. Its an 8*6 slab garden (48 slabs) but you can save some by reusing off cuts.

I'll tell you a secret, Knittedfairies - I wanted gravel.

When we moved in here three years ago this part of the garden was a horrible wilderness.

It was never an actual garden. You could not plant anything. There was just a membrane covered with shingle.

Our first attempt to improve it consisted of bark. Loads of bark.

That was a disaster because it never stops raining here in Argyll and there was no drainage.

Next we put down some artificial grass. it never lay flat and looked strange.

DH always said the best thing would be to lay slabs.

I thought (and still think) that gravel would be the easiest answer.

But he has set his heart on the slabs now.

I am sure that something will go wrong. They won't look right. I just have this feeling of doom about the whole project.

Especially as even the shop selling the fucking things couldn't work out how many we need.

It all seems - bonkers.

However - when it's done I shall take some photos and add them to the thread.

Poor old DH. He has worked so hard and we've bought so many lovely plant pots.

It seems a shame that he can't have his little patio without all this chaos.

12ft is 360cm 8ft is 240cm
240x 360 is 86400. 1 tile at 45cm
45into 360 is 8 tiles across
45cm into 240 is 5.3 so 6 tiles across.
8x6 46 tiles required. Some will need cutting but when thats done the left over part might not be able to be cut to fit another gap so 46 does it

See on page 1, I saw 36, 45 and54 slabs and the wine got the better of me.

But 45cnm is 1.5 foot. So 90cm is 3 foot. So 2x45 (to get 90) by 4 (to get 3->12 foot) is 2x4 =8 across

To get to 9 foot (closest to 8foot) is 2X3 is 6.

6x8=48.

I’m soo sorry that that isa different answer again but that’s what my brain says tonight.

It may work better in the morning. But a day of strategy and leadership, folllwed by wine, does that to the clearest thinkers!!

Thank you BiddyPop for sharing your latest answer with us this evening.

It has enhanced the thread.

Have a on me.

To the exact letter of the calculation you’ll need 44 - but that doesn’t account for off cuts/spares.

I assume B&Q’s calculator is a bit more accurate as it must take into account the extra pieces you may need to cut down, so I’d go for 50.

Wondering where the shop got 36 from

So anywhere between 43 and 48 slabs required. 36 isn't enough

Any advance on ThumbWitchesAbroad's answer from much earlier in the thread?

Bearing in mind the shop actually sold DH 34 and not 36 as I originally said (not having looked at the invoice properly) I am as bewildered as you mnthrowaway202020.

Weird! I’m going to give her the benefit of the doubt and assume she mistook 34 for 44

I wonder how many other customers she mis-sold tiles to!

My final suggestion is that you make the patio using the number of slabs you've bought. (It might not end up 12ft by 8ft though, but it will be fine.)

54, as a minimum. You'll probably need more to account for any damages you go.