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

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

On 19 Apr, 00:17, wrote:
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

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

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

Roger Moss wrote:
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

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