Tiling concrete floor without damp-proof membrane

[Roger Moss]

I am about to tile the concrete floor of a boiler hut. The floor is dry
- it is on sloping ground and well drained - but reading the
instructions on the bucket of tile adhesive for concrete floors, they
are quite particular that the floor should have a damp course.

Is this because once the floor has impermeable tiles over it, it will
get damp and the adhesive will dissolve back to a sticky state? Would I
be better sticking them down with mortar?

Thanks
Roger

[meow...@care2.com]

Roger Moss wrote:

> I am about to tile the concrete floor of a boiler hut. The floor is dry
> - it is on sloping ground and well drained - but reading the
> instructions on the bucket of tile adhesive for concrete floors, they
> are quite particular that the floor should have a damp course.
>
> Is this because once the floor has impermeable tiles over it, it will
> get damp

yes, no more large evaporation surface.

> and the adhesive will dissolve back to a sticky state?

no, it just loses some strength and fails early

> Would I
> be better sticking them down with mortar?

Most tile adhesives are modified cement mortars.

You could go the modern way, but there are plenty of old tiled
floors that have lasted a century plus with no dpc. A simple way
to help them achieve this is to use a grout that will evaporate any
damp.

NT

[ma...@atics.co.uk]

Dear all
..or you could use a water-"proof" epoxy mortar that acts as a dpc
(many on the market - consider Sika or Ardex?)
Chris

[Roger Moss]

meow...@care2.com wrote:>
> You could go the modern way, but there are plenty of old tiled
> floors that have lasted a century plus with no dpc. A simple way
> to help them achieve this is to use a grout that will evaporate any
> damp.
>
>

The stuff I've got is Unibond's "Tiling for concrete floors" extra
strong waterproof tile adhesive & grout - sounds just the stuff until
one reads the warning about needing a DPM. Presumably being waterproof
this wouldn't let damp evaporate?
- Roger

[Stuart Noble]

If the adhesive was waterproof, why would it need a dpm? If the floor is
dry now, I'd tile away. It's only Unibond trying to cover their arses.
If there is any damp in the future, precious little is going to
evaporate through the grout anyway