Preparing uneven concrete floor for tiling

[Dan Fitchie]

Hi, I have a small roughly 1 metre square porch area that we would like to put tile down on and am just looking for some advice as the area isn't without problems. The area is concrete which has quite the slope - between the bottom of the wooden step in the foreground of the image attached and the white front door there is a 3.5cm difference in height (slopes down to the front door). The other issue is the fact that the area directly below the front door, (which is actually part of the concrete front steps upto the door) gets damp in heavy prolonged rain. I've resealed the silicon at the bottom (there is a 1cm gap at the bottom of the door which opens to the outside - this is filled with sealant), cleaned out drain points on the door and tightened the door itself, replaced the rain strip on the outside of the door and still find dampness. I have a feeling the water is just soaking through the step itself over time.
How (if I can) can I prepare the area for tiles? I thought about putting a liquid damp proof membrane over all the concrete, but am not sure whether you can tile over that? I also don't know how to deal with the slope.
Thanks.

 

[Spare Tool]

If the moisture is soaking through the step not a lot you can do to stop that, maybe a good dowsing with Johnson's Waterseal on the step might help..
Inside a paint on epoxy dpm such as Ultra dpm it would stop the damp penetrating up into the adhesive and up through the grout, or possibly a strip of ducca or jacoboard type waterproof insulation board stuck down.. As for the slope, doesn't look like there's 35mm plus tile and adhesive to play with on the door casing? If not all you can do is make it the least slope possible using self leveler and tile it flat not level..

 

[Bond]

Very small area,I’d be inclined to break it out and lay new level floor incorporating insulation board and DPM, returned up walls and at door.

 

[Just Rizzle]

small area you could tank out using sbr and cement see sovereigns web sit on tanking solutions

 

[Bond]

small area you could tank out using sbr and cement see sovereigns web sit on tanking solutions

Tanking the existing floor, will protect the adhesive and tile, however the concrete floor is still damp and ultimately may transfer into wall, just something to bear in mind. Best dealing with the source of dampness ,level and insulate floor at same time.

 

[Dan Fitchie]

So just use a tanking slurry and sbr instead of going down the route of a dpm like the bostik cementone one? The dampness is actually only a very small amount appearing by the door. In the picture the darker area of the floor at the top is the outside step coming under the front door and butting up against whatever concrete slab the rest of the porch is made of - its the edge of the step nearest the door which is becoming damp. I just figured I'd need to put something down over the whole area to stop any tiling failing, I might be being dramatic.
In terms of levelling it, I'm wondering if I you think I actually need to? Maybe it's a stupid thing to suggest but with it being such a small area would tiles on a slight incline be an issue?
If I did need to and had to use whatever leveller to do so, the level it would need to come up to by the door would raise it to over the pvc frame below the door. Would there be any issues once it dries with it sitting against the pvc?
Can a levelling compound be used directly over a tanking slurry. I was reading other dpms need a 50mm screed over the top before levelling compound is used.
Cheers.

 

[Bond]

You could stick down a waterproof uncoupling membrane, and tile over. I see you have a crack just behind door threshold, between what may be the
concrete step and floor. No issues butting tile to door threshold, just use a flexible sealant instead of grout at that point.

 

[Dan Fitchie]

You could stick down a waterproof uncoupling membrane, and tile over. I see you have a crack just behind door threshold, between what may be the
concrete step and floor. No issues butting tile to door threshold, just use a flexible sealant instead of grout at that point.

Hi Bond, that's right, the crack is just the meeting point between floor and step. I've not come across uncoupling membrane before. Just having a quick read, and you just bed it in tike adhesive is that correct? Would the concrete floor need priming first?
The butting the door issue I mentioned was more about if I'd used some sort of levelling compound which was sat against the pvc frame, will use a sealant though where they meet.

 

[Bond]

Aye ,Dan, flexiable tile adhesive 3/4mm notched trowel to bed membrane,no need to prime ( although l gernerally do) good clean and dampen with sponge.