hello all, i need help, i bought some natural slate tiles from wickes last year and i now want to put them in my small hallway that is currently carpeted, there is a concrete floor underneath, could anybody advise me on floor prep as some people have told me i need a damp proof membrene underneath the tiles and some people say i dont, also i have been told slate is hard to seal and normally ends up in spotting, could anybody suggest a good product for sealing and what would happen if i didnt seal would they mark easily, thanks for any help

Is the floor concrete or sand cement screed? Is this calibrated or uncalibrated slate?

Basic info:

As far as prep is concerned, remove the carpet and all dust / adhesive residues. Get rid of any high spots with a localised "whack" with a hammer and bolster. Prime with an acrylic primer that is suitable for use with the single part flexible adhesive that you intend to use to fix the slate.

Use a 10mm half round trowel to apply the adhesive and cover the underside of the slate with a smooth skim of adhesive prior to fixing.

Seal the slate with either an impregnating sealer or colour enhancing sealer. I like to use LTP or Lithofin products depending on what final appearance you would like.

Grout with a flexible grout and then seal again.

Remember to ensure that the tiles are fully dry prior to applying a sealer otherwise you may end up sealing in moisture which may give the "milky" spotting that you refer to.

Good luck

Daz

Only thing to add there is, I give them a good clean and seal before laying. Usually scrubbing brush and hose pipe and seal when dry

Another couple of tips for you:

When you are grouting, work at getting the grout out of the little surface cracks while the grout is wet or you will end up with lines of grout where you don't want them.

You may need to wash them several times prior to sealing. The trick is rinsing the sponge with every wipe and methodically working over the floor. I did one last week (24 sq. mtrs) and the cleaning/grouting/sealing took nearly as long as the laying.

Re. the sealing I applied it with a 4" roller and then wiped over with a clean cloth the remove any surplus sealant leaving a good result.

Good info Sandy. However, beware of over wetting the grout when washing off and always follow the manufacturers instructions for applying the sealer.

Originally Posted by Captain Slow

Good info Sandy. However, beware of over wetting the grout when washing off and always follow the manufacturers instructions for applying the sealer.

Fair point...I actually used a washboy and I'm guessing Sammy doesn't have one so have altered my comments to suit ...and you're right about the sealer as different types may have different application methods.

hi all,

thanks for the info, i am no expert but i think the floor is concrete with a sand cement screed as it is smooth and has a cement look/colour?

do i need a damp proof membrene under the tiles and how would i know if i do?

and i think the slate is calibrated it does not say anything on the boxes but it is all the same size?

does anyone have any views on what kind of tile would be best for a busy hallway, hopefully with some slip resistance when wet and pretty maintence free?

Sammy,

i'm pretty sure that you have a sand cement screed and not concrete floor. There will have been a damp proof membrane installed prior to the floor screeding so I imagine that the advice you have been given is with regards to a decoupling membrane. I tend to use decoupling membranes for wooden floors as they eradicate lateral movement of which wooden floors are prone.

If the slate is of varying thickness, then you have an uncalibrated product. In this case, just sort through the tiles and grade them by thickness (usually 3 piles, thick, medium and thin). Use the thickest tiles for the high traffic areas of the floor working through the medium and using the thinest tiles for the edge cuts. When fixing uncalibrated stones I prefer to use a pourable thickbed adhesive (Mapei P4 is a good one and available via Tile Giant) so as to ensure a varying adhesive bed depth and 100% coverage on the back of the tiles.

I have done many slate hallways and know of no issues with slipping etc. so I'm sure they will be great . Here's a pic of one I did about a year ago....

dont fix with to tighter grout joint around 5mm is ok for the slate you have. and if you want to lift the colours in the slate after sealing and grouting . try some fila stone satin finish . will look great

hi captain slow,

you recommend mapei P4 to lay natural slate on, could i just ask have i got to prepare the substrate screed with anything mapei primer s, primer g, mapeprim sp, the house was built 1992 - 1996 if this makes any difference,
what grout would you use? and somebody suggested 5mm gaps is this about right?

what sealer would you reccomend as i looked and there is loads of different ltp or lithofin?

if it makes any difference the hallway will get cleaned often with water/mop and get water dragged in from outside when coming into house

thanks for your help
sammy

This mulicolour slate was fixed with Mapei fast set flexible direct onto a sand/cement screed, tiles sealed with sovereign stone seal and grouted with mapei Jasmin 130.

Originally Posted by Sammy

hi captain slow,

you recommend mapei P4 to lay natural slate on, could i just ask have i got to prepare the substrate screed with anything mapei primer s, primer g, mapeprim sp, the house was built 1992 - 1996 if this makes any difference,
what grout would you use? and somebody suggested 5mm gaps is this about right?

what sealer would you reccomend as i looked and there is loads of different ltp or lithofin?

if it makes any difference the hallway will get cleaned often with water/mop and get water dragged in from outside when coming into house

thanks for your help
sammy

If it is a sand cement screed then I would suggest priming with "Primer G". At least a 5mm gap is wise and I recommend you try fixing by eye so that you can adjust the grout widths due to possible size issues with the tiles.

As far as sealers go, LTP is ideal if you want a matt or satin finish, alternatively, the Lithofin slate seal will give you a gloss option.

Good luck.