hi room i have a area about 2700*3000 to screed the screed is going to be about 25mm thick can some one tell me is it better to buy sand and cement already mixed in bags or do it my self and how would i work out how much sand and cement i need thanks

In this case its basically all sand with a bit of cement so really its the volume of sand which is a bit over 0.2c/m and a 40kg bag or two of cement.

Your mix will reduce by about 25% when wetted up. So calculate the floor's volume and add a third:

2.7×3.0×0.025=0.2025m³

0.2025×4/3=0.27m³

Say you're making it 6:1 of Sand to Cement (definitely no stronger). Then you have:

0.27÷7=0.039m³ Cement
(0.27÷7)×6=0.231m³ Sand

A 20kg bag of cement is approximately 14 litres, or 0.014m³. So three bags will do.

Sand weighs about 1500kg/m³, so you need about 375kg. That's close enough to a half tonne delivered. Use the rest for the kids' sandpit, in the garden to break up clay soils, or give it away to a mate...

I think the bag mix is somewhat stronger (and therefore going to go off faster).

Regards, Adam.

I've posted how to do a screed before here, so if you search this site you'll find info on how to do it. you want to use a medium river sand (medium bedding sand) and a 4:1 sand cement mix. If you get 5 20kg bags of builders cement that should cover it.

Cheers
Michael

I will soon have to do the floor in my bathroom and am not looking forward to it.
Has anyone got any experience of using galvanised mesh in a screed which will only be about 30-40mm thick. I intend to put heating cables down and had been going to lay them on top of the screed until I saw this idea (refer photo attached). They lay the mesh on the concrete slab with the cable attached then screed over it.

My floor is about 3m x 2m. I thought the thinner guage galv mesh from Bunnies might be easier to work with than chicken wire? Can I just lay the mesh directly on the slab without raising it into the screed?

Is plastering sand suitable for the screed?



Cheers

__________________
Juan


"If the enemy is in range, so are you."

Yes and no. The general wisdom is to use a coarse sand since it will result in a stronger floor. I use a medium bedding sand, but I have done a few floors with washed pit sand - fine like plasterers sand a long while ago, and they are still fine.

Cheers
Michael

Hi mid-c,

Do you forsee any issues with laying a thin guage galv mesh on top of the slab like they have to attach the cable to?

Cheers

__________________
Juan


"If the enemy is in range, so are you."

will be fine if it is flat. awfully difficult to deal with mesh that springs up through the screed.

Cheers
Michael