sand blinding

[dotto]

Hi guys. i am in the process of tiling the floor of my bathroom. The subfloor is concrete all over ( 0ld house 1910) and the last 1.5 square meter has a lower step 30mm deep which a want to bring level with the rest of the concrete floor by pouring a mix of sand and cement before tiling all over the floor. Also that lower step has affected by what i suppose is rising damp. Before i pour the mix of sand and cement i want to brush a couple of coats of bitumen to form a dpm. My questions are:
1) Do i have to wet the concrete substrate before i apply the coats of bitumen?
2) Once i have applied the 2 coats of bitumen, do i have to sprinkle some sharp sand when the bitumen is still tacky in order to create a grip for the sand and cement mix?
3) Is the ratio 2 sharp sand:3 cement OK to bring the 30mm lower step level with the rest of the floor?
4) I want to be able to tile asap ( ideally after 24 hours) is there any cement or mixture that goes off that quick for a depth of 30mm? Thank you for your pieces of advice.

 

[mointainwalker]

I want to be able to tile asap ( ideally after 24 hours) is there any cement or mixture that goes off that quick for a depth of 30mm? Thank you for your pieces of advice

I don't know about drying times of any other materials, but you ought to wait 30 days before tiling on a mortar screed of this thickness or the tiles will likely lift.

 

[tim00]

1. If the lower step is affected by damp then the remainder of the slab will also be damp affected - hence, apply a liquid membrane across the whole surface. Ref. bitumen, read the instructions.
2. Damp prevented from dissipating thro the floor might find another outlet in the surrounding walls.
3. You can "sprinkle sand" to provide a tack, or prior to screeding, apply a creamy "wash" of water and cement.
4. Screed 4:1 to a depth of 50mm ( screed depth is a contentious issue ). But work the depth of screed/FFL to adjoining FFL's.
5. Give drying time as long as possible ( 3-5 days ), and test ( knock ) the dry screed to test for hollows, or lifting, before tiling.
6. Try johnbridge.com for brilliant advice on all things tile.

 

[dotto]

Hi guys and thanks for the advice. Tim00, what do you mean by FFL? I know of Ardex slc which can go up to a depth of 35mm and I can tile after only 24hours but it is expansive, that's why I wanted to go the sand and cement way provided it would not take too long to dry as I do not have much time to play with..... BTW 4:1 is it 4 sharp sand to 1 cement or the other way round? Thanks again.

 

[McHaleBuildingServices]

FFL = finished floor level

 

[dotto]

thanks m8

 

[seasickstevie]

... is it 4 sharp sand to 1 cement or the other way round?

The '1' is the cement.