How do I calculate material needed for screed floor? inc pic

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TonyLikeDIY

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Hi,

How do I calculate how much cement, ballast and/or sand I need to make a screed floor. (Im not sure if I need ballast or just sand it needs to be strong as I am using this space as a gym?)

The size of screed will be 5500 x 5300 x 75mm.

Below is a pic of the where the screed will go.

Cheers,

Tony

- - -
 
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Actually I got the one above WRONG. that calculation was for concrete. The one below is for a screed?

Its the same volume but are the parts correct? I was told i need ballast

Cheers

Tony

 
You will need about 3.5 tonnes of sharp sand and 30-35 bags of cement, to screed the floor.
 
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So the 41 bags of cement and 123 bags of sand that they show (im assuming sharp sand) is not correct? for 75mm? or are u basing this on just an adequate screed depth and not 75mm?
 
After much research....

I have found for 25mm thickness i need 14 bags of cement and 41 bags of sand which equates to 350kg of cement to 1025kg of sand.

1) Am i correct in assuming 1025kg of sand is one tonne ie 1 jumbo bag? Its just the guy in the shop said i need 2 jumbo bags!!!

2) This is based on 4:1 but should i go for a 3:1 ratio?

3) Is 25mm to thin for a screed (its for a gym floor). Is 50mm the norm?

Cheers,

Tony
 
Hi,

Are there any people on here that know about screeds?

I now know I want 50mm thickness but this means I need 28 bags of cement (700kg) and 82 bags of sand (2050kg). This was on a calc for 4:1 I think. Is this correct?

Please can anyone help as I am looking to buy and pick up the cement today and buy the sand so it can be delivered on Monday?

PS: IS THE 2050KG OF SAND = 2 JUMBO BAGS?
 
Hi, i saw that post but didnt know the rational behind it. The website calculators are telling me different,

Cheers

Tony
 
Ok DIY guys, I now have 6 tonne of sand on my driveway so how much cement do i need for a 1 to 4 screed?

I don't know how to calculate the cement as the density is different. This is how I calculated the sand.

Length = 5.5 m
Width = 5.3 m
Depth = 75 mm
Area = 29.15 m2
Volume = 2.18625 m3

Volume x 2.6 = 5.68 tonnes (which I rounded up to 6 tonnes)

Also, is underfloor heating a waste of time? and should i put in some sort of rigid insulation first?

Cheers,

Tony
 
tony, you were given the answer by noseall. :rolleyes:

why do you ask a question then answer it yourself ? look at the posts they are all yours barring 2 :confused:
 
LOL - there is a bloody sticky at the top of the building forum, which has been there years!

Anyway, why do you want to screed a loft :eek:
 
alastairreid said:
tony, you were given the answer by noseall. :rolleyes:

why do you ask a question then answer it yourself ? look at the posts they are all yours barring 2 :confused:
Click to expand...

I didnt know so asked for the rationalle behind 3.5 tonnes of sharp sand and 30-35 bags of cement by noseall. I always like to know or establish the reasons rather than just going by what people just say without a scientific reasoning behind it. As somebody else could say something else and I would then have to make an informed decision.

In regards to answering my own posts, I was needing this info quick so started to do my own research on the net and also asked a few builders, engineers, and construction project managers I know. I posted them to ask you guys for advice on what I have found out as I thought you guys might be more experienced if this is your field of expertise If I could get the rational behind 3.5 tonnes of sharp sand and 30-35 bags of cement then I will go with this. (I dont think I answered any of my posts as I think they were all phrased as questions but I hadnt got any replies!)

However, all the web calculators and all the people I have asked since starting this post (bar noseall) get the answer 5 to 6 tonnes of sand! That is why I am still investigating as I am at present puzzled by nosealls reply.

Noseall, is there a calc or rational behind this?

alastairreid, if you agree with this and know how it was derived could you let me know?

Thanks in advance

Tony
 
tony, go to the top of the building forum and click on the screed estimator this will give you your quantities.
 
Thanks.

My builder did the screed today whilst I was at work but when I got home it looked a little wet and bumpy (I thought this was laid as a dry mix!). I told him 1 to 4 ratio (and 8 bags of cement to every tonne of sand).

Also, I asked him if he was going to use a paddle mixer but he said no and that he was going to use a normal cement mixer (i was worried about lumps). I also asked him about using plasticiser but he said that it is only needed when building walls and using building sand. Is he having me on?

I rang him about the bumpiness on the surface over the phone just now and he said that he will be back in the morning to make it nice and smooth? Is this the right way to do this?

I took some photos showing how wet and bumpy it looks right now.

Tony

 
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