Best and cost effective way to build up sub-base below marble tiles - TilersForums.com

[Ronin63]

Good day everyone! I have a small question, i need advice on. I have a project where a typical screed allowance, on top of the concrete slab, is 100mm. I deduct 20 to 30mm for the marble tile and the balance for concrete screed and adhesive. In this situation the allowance is 200mm to top of finished floor. All that additional concrete screed is expensive. I'm told some people use sand. What type of sand can you use in this situation? and what would be involved in compaction, so no cracks would arrive at a later date?

Thank you. Timothy

 

[hk940]

I have used sharp mason sand and Portland cement ratio of 3 or 4 to 1 (sand to cement) for over 50 years.
The biggest job was for a private boy's high school 8,000 square feet that was over 23 years ago with no problems.
Just before placing the mud paint the floor with a slurry of either Portland or the mortar adhesive you will be using
That mix ratio is plenty strong, I helped my cousin do a power plant in Idaho it was 64,000 sg. ft. and used that mix, compact well, screed off, then steel trowel.

 

[Ronin63]

Currently the project is in Saudi Arabia, The local CM's have said, that it is local practice, to just lay down red sand, compact it, then make up a highly liquid solution of white cement and water and splash it down on top of the sand and then lay down your marble/stone/ceramic etc, and they never have had any problems with cracking.(though I'm skeptical they've come back years later to see if there was any floor movement and the grout had any crack lines.

 

[hk940]

That is not something I have ever heard of. I just don't know how well the white cement mixture would mix with the sand.
I would do a test section with out setting any thing, and see how hard the sub bed got.