Hi,

Got 8 bags of Cempolatex that's going down in a couple of weeks.

Will be using a series of guide rails to ensure correct levels and laying in
1-.5m wide stripes for practical reasons (large room).

One thing occurs to me: I have engineered a controlled slope in the centre
section of the room (12mm in about 2m TBC)[1].

The compound will be going on between 1mm and 8mm thick typically in this
region. Am I likely to have trouble keeping it on this slight slope - ie is
it likely to try to slump towards the lower end? The top end is likely to
only be 2-4mm thick.

[1] Levelling the whole floor is out of the question - I would need 10 bags
just to sort out half the room, then probably another 6 to complete. And
there would be level mismatches at the hall door of 8-10mm.

Cheers

Tim

Tim S wrote:
Hi,

Got 8 bags of Cempolatex that's going down in a couple of weeks.

Will be using a series of guide rails to ensure correct levels and laying in
1-.5m wide stripes for practical reasons (large room).

One thing occurs to me: I have engineered a controlled slope in the centre
section of the room (12mm in about 2m TBC)[1].

The compound will be going on between 1mm and 8mm thick typically in this
region. Am I likely to have trouble keeping it on this slight slope - ie is
it likely to try to slump towards the lower end? The top end is likely to
only be 2-4mm thick.

Shouldn't be a problem. It basically stays where you put it, and doesn't
self level. Where I had trouble was joining the separate sections. It
sets hard quite quickly and you may find it difficult to smooth the
edges where the guides have been. I think I had to use a disc sander at
one point, but I had mistakenly left it overnight.
Using dabs of screed rather than "rails" might work better. If you lay a
straightedge down and pack it out underneath, you should get an accurate
height.


[1] Levelling the whole floor is out of the question - I would need 10 bags
just to sort out half the room, then probably another 6 to complete. And
there would be level mismatches at the hall door of 8-10mm.

Cheers

Tim

On 29 May, 10:54, Stuart Noble wrote:

Shouldn't be a problem. It basically stays where you put it, and doesn't
self level.

That depends rather on the compound. I used some F Ball Stopgap 300
last weekend which really is a self-leveller, rather than a self-
smoother. Amazing stuff. Slight push with a trowel to spread it,
spiked roller, and 5 mins later it is flat and level.

The others I've used (Sika, and BAL Multibase) behave more like your
description.

Mapei Ecoplan Ultra is another one which is supposed to be a real self-
leveller.

Where I had trouble was joining the separate sections. It
sets hard quite quickly and you may find it difficult to smooth the
edges where the guides have been. I think I had to use a disc sander at
one point, but I had mistakenly left it overnight.

Yes, best to get at it while it is 'green' and can be scraped with a
trowel.

My tip: in this weather, cover the windows to ensure shade - if the
sun gets to it it will go off before you know it.

DAMKHIT, but it involved cursing, a shovel, something awaiting
disposal on my patio which looks a bit like a grey elephant dung
sculpture, and a few extra bags of SLC (at which point the Stopgap
came into the equation, so it wasn't all bad)..

wrote:
On 29 May, 10:54, Stuart Noble wrote:

Shouldn't be a problem. It basically stays where you put it, and
doesn't self level.

That depends rather on the compound. I used some F Ball Stopgap 300
last weekend which really is a self-leveller, rather than a self-
smoother. Amazing stuff. Slight push with a trowel to spread it,
spiked roller, and 5 mins later it is flat and level.

I used some Wickes 'Master' Latex Floor Levelling Compound today & it was
incredible. Never used anything like it before.

http://www.wickes.co.uk/Special-Mort...nd/invt/154134

Whats with the spiked roller? I did actually read the instructions on the
bag of Wickes stuff & no mention there?


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

Whats with the spiked roller? *I did actually read the instructions on the
bag of Wickes stuff & no mention there?

It helps to agitate it a bit, gently, after the spreading, which
encourages levelling, and it releases any entrained air to stop
bubbles on the surface. It's a trick of the trade, like pin levellers/
wiper blades etc, rather than a requirement which would be mentioned
on the bag.

Interesting about the Wickes stuff, I wonder who makes it. What kind
of area/depth did you do, and what kind of error against a level did
it end up with?

There are so many of these things, and they seem to vary hugely - I've
got limited first hand experience but it bears that out. Pro tilers
and karndean-type (even fussier requirements) installers certainly
think so as well (and know a lot more than I do about it). The latter
can get away with very little in terms of flaws in the substrate, and
is where I got the Stopgap 300 tip from.

Stuart Noble coughed up some electrons that declared:


Shouldn't be a problem. It basically stays where you put it, and doesn't
self level. Where I had trouble was joining the separate sections. It
sets hard quite quickly and you may find it difficult to smooth the
edges where the guides have been. I think I had to use a disc sander at
one point, but I had mistakenly left it overnight.
Using dabs of screed rather than "rails" might work better. If you lay a
straightedge down and pack it out underneath, you should get an accurate
height.

Thanks Stuart. Sounds promising.

I'll watch out for the edges. The guides will be ali channel, set so that a
scraper bar levels the screed to the *bottom* of the rail. Cling film will
be used to ensure a release of the guide. Alternate strips will be done,
the edges sanded or trimmed as necessary to remove any bits the crept up,
then the remaining strips will be laid without rails (ie scraped level with
neigbouring strips).

I'll report on the success of otherwise of this method. But it does have the
advantage that all the pratting around is done "dry". Once the rails are
set on their studs, it's *should* be pour n scrape. That's the idea
anyway...

Cheers

Tim

On Thu, 28 May 2009 22:23:23 +0100, Tim S wrote:

Hi,

Got 8 bags of Cempolatex that's going down in a couple of weeks.

Will be using a series of guide rails to ensure correct levels and laying in
1-.5m wide stripes for practical reasons (large room).

One thing occurs to me: I have engineered a controlled slope in the centre
section of the room (12mm in about 2m TBC)[1].

The compound will be going on between 1mm and 8mm thick typically in this
region. Am I likely to have trouble keeping it on this slight slope - ie is
it likely to try to slump towards the lower end? The top end is likely to
only be 2-4mm thick.

[1] Levelling the whole floor is out of the question - I would need 10 bags
just to sort out half the room, then probably another 6 to complete. And
there would be level mismatches at the hall door of 8-10mm.

Cheers

Tim

Yes, I used Cempolatex recently and was not impressed. As everyone
says here, it does not really self-level. It's also very expensive for
what it is. I hope to make up the dips by getting the levels right
with adhesive before I lay the Marmox board!
Maris

wrote:
Whats with the spiked roller? I did actually read the instructions
on the bag of Wickes stuff & no mention there?

It helps to agitate it a bit, gently, after the spreading, which
encourages levelling, and it releases any entrained air to stop
bubbles on the surface. It's a trick of the trade, like pin
levellers/ wiper blades etc, rather than a requirement which would be
mentioned on the bag.

Ah. Good tip. There were a few surface bubbles, but the tile adhesive will
cope with those easily.

Interesting about the Wickes stuff, I wonder who makes it. What kind
of area/depth did you do, and what kind of error against a level did
it end up with?

It was a porch 6' x 3' approx. From the initial check with a level, one
corner was down by about 10mm, rest of it was a roller coaster for a mouse.
Hard to get a level when it keeps rocking, don't know where you are.

Ended up like a bloody billiard table, hence me being so impressed with the
stuff.

The client had the porch built by a national DG company who initially quoted
'including base' but when it came to doing the job claimed it was 'base
extra'. Harsh words were apparently exchanged & the client reckoned the
base was put down in a rush.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk

Maris coughed up some electrons that declared:

Yes, I used Cempolatex recently and was not impressed. As everyone
says here, it does not really self-level. It's also very expensive for
what it is. I hope to make up the dips by getting the levels right
with adhesive before I lay the Marmox board!
Maris

In my case, it might be a good thing... I'm going to scrape the stuff to the
finished level, then I want it to stay there...

Got mine cheap, at under 1/2 price (12 quid vs 30 quid)

Hoever, for a few other areas of minor imperfection, I was very interested
in the other products mentioned in this thread

You using Marmox too? So am I. Partly to get a DPM, partly to stop the floor
tiles going 5-6 degrees colder than the room in winter.

What adhesive are you using?

Cheers

Tim

On 29 May, 23:35, "The Medway Handyman"
wrote:
It was a porch 6' x 3' approx. *From the initial check with a level, one
corner was down by about 10mm, rest of it was a roller coaster for a mouse.
Hard to get a level when it keeps rocking, don't know where you are.

Ended up like a bloody billiard table, hence me being so impressed with the
stuff.

I ended up with the Sika & BAL stuff basically trying to level it with
a trowel, and then hoping the trowel marks would disappear- far too
much skill required, so there were bits which were at least 2/3mm
out. The F Ball stuff is consistently level to within a mm over the
length of an 1800 level,and just so easy that I will never bother with
anything else (assuming I need SLC again).

The guides will be ali channel, set so that a
scraper bar levels the screed to the *bottom* of the rail.

I rigged up a similar arrangement in wood for rendering a wall.
I found it easier if the scraper bar was a couple of inches shorter than
the width between the guides to allow some side to side movement. The
angle of the scraper also needs to be constant as there is a temptation
to rotate it to get a better edge.
I still ended up with some shallow indents where the guides had been and
these were more difficult to patch than deeper grooves. Your ali system
might be more accurate
Good luck with it. Won't half do your back in if you can't kneel between
the channels :-)

On Fri, 29 May 2009 23:38:01 +0100, Tim S wrote:

Maris coughed up some electrons that declared:

Yes, I used Cempolatex recently and was not impressed. As everyone
says here, it does not really self-level. It's also very expensive for
what it is. I hope to make up the dips by getting the levels right
with adhesive before I lay the Marmox board!
Maris

In my case, it might be a good thing... I'm going to scrape the stuff to the
finished level, then I want it to stay there...

Got mine cheap, at under 1/2 price (12 quid vs 30 quid)

Hoever, for a few other areas of minor imperfection, I was very interested
in the other products mentioned in this thread

You using Marmox too? So am I. Partly to get a DPM, partly to stop the floor
tiles going 5-6 degrees colder than the room in winter.

What adhesive are you using?

Cheers

Tim
The Marmox instruction leaflet says that a cement-based adhesive
should be used so I bought some Screwfix 'No Nonsense' tile adhesive,
which seems to meet the requirement. I'm using the Marmox to replace
the 50mm screed that I have removed and which was in poor shape. I am
installing a wetroom so I am having to incorporate a Marmox 20mm
showerstone base, which means using combinations of Marmox under that
to make up the level to 50mm. Marmox as a DPM? Hmm. I'm installing
underfloor heating over the Marmox, by the way.
Cheers, Maris

Maris coughed up some electrons that declared:


The Marmox instruction leaflet says that a cement-based adhesive
should be used so I bought some Screwfix 'No Nonsense' tile adhesive,
which seems to meet the requirement. I'm using the Marmox to replace
the 50mm screed that I have removed and which was in poor shape. I am
installing a wetroom so I am having to incorporate a Marmox 20mm
showerstone base, which means using combinations of Marmox under that
to make up the level to 50mm. Marmox as a DPM? Hmm. I'm installing
underfloor heating over the Marmox, by the way.
Cheers, Maris

Interesting. The concrete under my screed is as rough as a camel's arse so
I'm putting down 25mm SBR modified sand/cement screed to even that out,
then marmox. UFH in the 2 areas where I'm back to the concrete as I have
room for extra marmox. No UFH everywhere else as I decided I'll be bleeding
heat away left right and centre.

It was Marmox technical who told me that marmox could be used as a DPM
provided I sealed the joints (silicone or tape). I actually rang them to
ask how to fix it to a damp subfloor. The said plug and screw, and if I
prefered adhesive, I would need to speak to the adhesive manufacturer.

I did do that (Mapei) who recommended (but couldn't absolutely guarantee)
Keraquick. So that's what I'm going with.

What UFH heating are you going for?

Cheers

Tim

On Sun, 31 May 2009 21:02:34 +0100, Tim S wrote:

Maris coughed up some electrons that declared:


The Marmox instruction leaflet says that a cement-based adhesive
should be used so I bought some Screwfix 'No Nonsense' tile adhesive,
which seems to meet the requirement. I'm using the Marmox to replace
the 50mm screed that I have removed and which was in poor shape. I am
installing a wetroom so I am having to incorporate a Marmox 20mm
showerstone base, which means using combinations of Marmox under that
to make up the level to 50mm. Marmox as a DPM? Hmm. I'm installing
underfloor heating over the Marmox, by the way.
Cheers, Maris

Interesting. The concrete under my screed is as rough as a camel's arse so
I'm putting down 25mm SBR modified sand/cement screed to even that out,
then marmox. UFH in the 2 areas where I'm back to the concrete as I have
room for extra marmox. No UFH everywhere else as I decided I'll be bleeding
heat away left right and centre.

It was Marmox technical who told me that marmox could be used as a DPM
provided I sealed the joints (silicone or tape). I actually rang them to
ask how to fix it to a damp subfloor. The said plug and screw, and if I
prefered adhesive, I would need to speak to the adhesive manufacturer.

Are you sure they understood what a DPM is? Their instructions do say
about sealing joints with silicone but I assumed that that was to stop
water from the walk-in shower leaking into the subfloor i.e the other
way round! Why is your subfloor damp? That's a bit suspect straight
away. Strangely enough I'm finding strange things in my 20 year old
extension (built by previous owner). I was drilling through the wall
from inside at low level to take the waste and was getting damp sand
coming back out. Has my cavity been bridged? Wondering whether to
remove a brick/block at low level. The outside DPC is much higher than
the inside DPC because the garden rises behind the extension.
However not sure about the inside DPC at all - I thought it was the
plastic membrane under the concrete slab turned up but it seems to be
a DPC, in fact, not connected to the slab at all!
Anyway, back to the subject in hand, I'm using electric UFH, which
takes up very little thickness and will go in the tile adhesive. I'm
using pebble tiles on top of the Marmox and am now getting worried
about pressure on it impacting the Marmox because they recommend solid
tiles!
Cheers,
Maris


I did do that (Mapei) who recommended (but couldn't absolutely guarantee)
Keraquick. So that's what I'm going with.

What UFH heating are you going for?

Cheers

Tim

Maris coughed up some electrons that declared:

On Sun, 31 May 2009 21:02:34 +0100, Tim S wrote:


Are you sure they understood what a DPM is? Their instructions do say
about sealing joints with silicone but I assumed that that was to stop
water from the walk-in shower leaking into the subfloor i.e the other
way round!

Yes, they understood. They volunteered that it would act as a DPM as it was
waterproof and vapour proof in either direction ;-


Why is your subfloor damp? That's a bit suspect straight
away.

Not really. The house is nearly 60 years old and has variable dodgey floor
construction.

In some parts there does appear to be a DPM of sorts under the screed over
the concrete. In other parts there isn't. Under one bit of lino I lifted,
it had been damp - black mould and dark patch on floor.

The same house has 12" foundations on clay - that's broken by modern
standards, but the house has survived perfectly well.

It's just the old ways...

Strangely enough I'm finding strange things in my 20 year old
extension (built by previous owner). I was drilling through the wall
from inside at low level to take the waste and was getting damp sand
coming back out. Has my cavity been bridged?

If the damp sand is lower than the DPC it's nothing to worry about - that's
normal.

If it's above it may bridge, but the practical effects will vary - it might
be no problem or it might be a serious problem. Depends how much bridging,
how wet the outside wall gets etc.

The real test - do you actually have any damp problems inside in that area.
If not, don't worry.

Wondering whether to
remove a brick/block at low level. The outside DPC is much higher than
the inside DPC because the garden rises behind the extension.
However not sure about the inside DPC at all - I thought it was the
plastic membrane under the concrete slab turned up but it seems to be
a DPC, in fact, not connected to the slab at all!


Anyway, back to the subject in hand, I'm using electric UFH, which
takes up very little thickness and will go in the tile adhesive. I'm
using pebble tiles on top of the Marmox and am now getting worried
about pressure on it impacting the Marmox because they recommend solid
tiles!
Cheers,
Maris


That sounds cool.

On the Marmox loading - it has a compressive strength of 30 tonnes/m2. I've
got some - the foam is fairly soft but the glass mesh surface is rock hard.

Are you likely to get a seriously high point loading anywhere that could
push your pebbles down?

Is this a bathroom? If so, perhaps you could mitigate it by putting the bath
on bearer planks (I will) and perhaps using a normal tile under the loo
base. Otherwise I can't see a bathroom area getting much other high
loadings.

Kitchens would be different - table legs and worktop legs...

Cheers

Tim

On Mon, 01 Jun 2009 19:00:37 +0100, Tim S wrote:

Maris coughed up some electrons that declared:

On Sun, 31 May 2009 21:02:34 +0100, Tim S wrote:


Are you sure they understood what a DPM is? Their instructions do say
about sealing joints with silicone but I assumed that that was to stop
water from the walk-in shower leaking into the subfloor i.e the other
way round!

Yes, they understood. They volunteered that it would act as a DPM as it was
waterproof and vapour proof in either direction ;-


Why is your subfloor damp? That's a bit suspect straight
away.

Not really. The house is nearly 60 years old and has variable dodgey floor
construction.

A 60 year old house should not have variable dodgy floor construction!
cavity walls had long been invented by then (not that that has
anything to do with floor construction but you get the drift).

In some parts there does appear to be a DPM of sorts under the screed over
the concrete. In other parts there isn't. Under one bit of lino I lifted,
it had been damp - black mould and dark patch on floor.

The DPM should be under the concrete slab!

The same house has 12" foundations on clay - that's broken by modern
standards, but the house has survived perfectly well.

Erk!
It's just the old ways...

Strangely enough I'm finding strange things in my 20 year old
extension (built by previous owner). I was drilling through the wall
from inside at low level to take the waste and was getting damp sand
coming back out. Has my cavity been bridged?

If the damp sand is lower than the DPC it's nothing to worry about - that's
normal.

Except that I'm not sure if the plastic is the DPC. By rights I should
have been perforating the dpc/dpm with my drilling but I didn't come
across anything.

If it's above it may bridge, but the practical effects will vary - it might
be no problem or it might be a serious problem. Depends how much bridging,
how wet the outside wall gets etc.

The real test - do you actually have any damp problems inside in that area.
If not, don't worry.

Wondering whether to
remove a brick/block at low level. The outside DPC is much higher than
the inside DPC because the garden rises behind the extension.
However not sure about the inside DPC at all - I thought it was the
plastic membrane under the concrete slab turned up but it seems to be
a DPC, in fact, not connected to the slab at all!


Anyway, back to the subject in hand, I'm using electric UFH, which
takes up very little thickness and will go in the tile adhesive. I'm
using pebble tiles on top of the Marmox and am now getting worried
about pressure on it impacting the Marmox because they recommend solid
tiles!
Cheers,
Maris


That sounds cool.

On the Marmox loading - it has a compressive strength of 30 tonnes/m2. I've
got some - the foam is fairly soft but the glass mesh surface is rock hard.

I noticed that I made indentations when I knelt down on the Marmox to
do something. Point loads definitely do have an effect.

Are you likely to get a seriously high point loading anywhere that could
push your pebbles down?

Is this a bathroom? If so, perhaps you could mitigate it by putting the bath
on bearer planks (I will) and perhaps using a normal tile under the loo
base. Otherwise I can't see a bathroom area getting much other high
loadings.

Yes, it's a wetroom, with a shower but no bath.
Maris

Kitchens would be different - table legs and worktop legs...

Cheers

Tim

Maris wrote:
On Mon, 01 Jun 2009 19:00:37 +0100, Tim S wrote:

Maris coughed up some electrons that declared:

On Sun, 31 May 2009 21:02:34 +0100, Tim S wrote:

Are you sure they understood what a DPM is? Their instructions do say
about sealing joints with silicone but I assumed that that was to stop
water from the walk-in shower leaking into the subfloor i.e the other
way round!
Yes, they understood. They volunteered that it would act as a DPM as it was
waterproof and vapour proof in either direction ;-


Why is your subfloor damp? That's a bit suspect straight
away.
Not really. The house is nearly 60 years old and has variable dodgey floor
construction.

A 60 year old house should not have variable dodgy floor construction!
cavity walls had long been invented by then (not that that has
anything to do with floor construction but you get the drift).

In some parts there does appear to be a DPM of sorts under the screed over
the concrete. In other parts there isn't. Under one bit of lino I lifted,
it had been damp - black mould and dark patch on floor.

The DPM should be under the concrete slab!


No, it should not.

Generally et conct=rete slab is 'below damp' laid on hardciore and soil.
If you dpm under that it waill rip and tear.

Normally 60 years old menas they painted the concrete with bitumen
before screeding. Liable to fail in time. Also may be bridging if screed
below DPC level on walls..




Except that I'm not sure if the plastic is the DPC. By rights I should
have been perforating the dpc/dpm with my drilling but I didn't come
across anything.

See above. It may be bitumen.

Yes, it's a wetroom, with a shower but no bath.
Maris

I laid slates and tiles straight on the screed here. Its fine. Just use
waterproof grout. And tile up a fair way on the walls as well.

Maris coughed up some electrons that declared:


A 60 year old house should not have variable dodgy floor construction!
cavity walls had long been invented by then (not that that has
anything to do with floor construction but you get the drift).

We have cavity walls. Just no consistent floor DPM. We do have consistent
wall DPCs.

The DPM should be under the concrete slab!

Look - don't mean to be rude, but can we drop it. My house is not upto
modern standards - I don't care how it's supposed to be - it is as it is.
Mostly it has no *serious* problems, just minor easily fixed ones (and the
lack of DPM is minor and easily fixed - we are not swimming in a lake here,
water ingress is mostly vapour)

On the whole, it's better built than most of the modern stuff: bricks
through and through and decent timber and despite the lack of deep
foundations and DPMs I would bet that it will outlive half the ticky tacky
crap that passes for building technology these days.

The same house has 12" foundations on clay - that's broken by modern
standards, but the house has survived perfectly well.

Erk!

Likewise - it is still standing. The only cracks are where some dickhead
removed most of the bricks under the fire opening lintel.

It's just the old ways...

^^^^ !!!!

;-


I noticed that I made indentations when I knelt down on the Marmox to
do something. Point loads definitely do have an effect.

Are you likely to get a seriously high point loading anywhere that could
push your pebbles down?

Is this a bathroom? If so, perhaps you could mitigate it by putting the
bath on bearer planks (I will) and perhaps using a normal tile under the
loo base. Otherwise I can't see a bathroom area getting much other high
loadings.

Yes, it's a wetroom, with a shower but no bath.
Maris

Are your pebble tiles individual "pebbles" on a mesh that lay a bit like
mosaic tiles, then you grout the tile as well as between all the tiles
yourself?

If so, and if you are noticing point load indentations, then personally I
would change the tile type. Same for mosaic. You have to lay them with a
flexible adhesive and grout out of necessity with marmox.

With no particular assumptions on how much you weigh, 30t/m2 equates to a
100kg fat bloke standing on a 5cm x 5cm area, approx. It's easy to see how
your knee made an indent as the area of contact is much smaller - 50kg
would be a very thin bloke.

Therefore, I would reckon on 10cm tiles being the absolute limit on size -
you need a margin for dynamic load vs static load (eg jumping).

Cheers

Tim

On Tue, 02 Jun 2009 08:07:47 +0100, Tim S wrote:

Maris coughed up some electrons that declared:


A 60 year old house should not have variable dodgy floor construction!
cavity walls had long been invented by then (not that that has
anything to do with floor construction but you get the drift).

We have cavity walls. Just no consistent floor DPM. We do have consistent
wall DPCs.

The DPM should be under the concrete slab!

Look - don't mean to be rude, but can we drop it. My house is not upto
modern standards - I don't care how it's supposed to be - it is as it is.
Mostly it has no *serious* problems, just minor easily fixed ones (and the
lack of DPM is minor and easily fixed - we are not swimming in a lake here,
water ingress is mostly vapour)

Sorry Tim I'll shut up!

On the whole, it's better built than most of the modern stuff: bricks
through and through and decent timber and despite the lack of deep
foundations and DPMs I would bet that it will outlive half the ticky tacky
crap that passes for building technology these days.

The same house has 12" foundations on clay - that's broken by modern
standards, but the house has survived perfectly well.

Erk!

Likewise - it is still standing. The only cracks are where some dickhead
removed most of the bricks under the fire opening lintel.

It's just the old ways...

^^^^ !!!!

;-


I noticed that I made indentations when I knelt down on the Marmox to
do something. Point loads definitely do have an effect.

Are you likely to get a seriously high point loading anywhere that could
push your pebbles down?

Is this a bathroom? If so, perhaps you could mitigate it by putting the
bath on bearer planks (I will) and perhaps using a normal tile under the
loo base. Otherwise I can't see a bathroom area getting much other high
loadings.

Yes, it's a wetroom, with a shower but no bath.
Maris

Are your pebble tiles individual "pebbles" on a mesh that lay a bit like
mosaic tiles, then you grout the tile as well as between all the tiles
yourself?

They are on a mesh. Have to grout between all the pebbles too but I'm
thinking that that will give it the required rigidity.

Cheers,
Maris

If so, and if you are noticing point load indentations, then personally I
would change the tile type. Same for mosaic. You have to lay them with a
flexible adhesive and grout out of necessity with marmox.

With no particular assumptions on how much you weigh, 30t/m2 equates to a
100kg fat bloke standing on a 5cm x 5cm area, approx. It's easy to see how
your knee made an indent as the area of contact is much smaller - 50kg
would be a very thin bloke.

Therefore, I would reckon on 10cm tiles being the absolute limit on size -
you need a margin for dynamic load vs static load (eg jumping).

Cheers

Tim

On Tue, 02 Jun 2009 00:27:08 +0100, The Natural Philosopher
wrote:

Maris wrote:
On Mon, 01 Jun 2009 19:00:37 +0100, Tim S wrote:

Maris coughed up some electrons that declared:

On Sun, 31 May 2009 21:02:34 +0100, Tim S wrote:

Are you sure they understood what a DPM is? Their instructions do say
about sealing joints with silicone but I assumed that that was to stop
water from the walk-in shower leaking into the subfloor i.e the other
way round!
Yes, they understood. They volunteered that it would act as a DPM as it was
waterproof and vapour proof in either direction ;-


Why is your subfloor damp? That's a bit suspect straight
away.
Not really. The house is nearly 60 years old and has variable dodgey floor
construction.

A 60 year old house should not have variable dodgy floor construction!
cavity walls had long been invented by then (not that that has
anything to do with floor construction but you get the drift).

In some parts there does appear to be a DPM of sorts under the screed over
the concrete. In other parts there isn't. Under one bit of lino I lifted,
it had been damp - black mould and dark patch on floor.

The DPM should be under the concrete slab!


No, it should not.

Yes it should.
http://www.diydoctor.org.uk/projects/dpc.htm to name just one
reference source (to include also my architectural education).

Cheers,
Maris


Generally et conct=rete slab is 'below damp' laid on hardciore and soil.
If you dpm under that it waill rip and tear.

Normally 60 years old menas they painted the concrete with bitumen
before screeding. Liable to fail in time. Also may be bridging if screed
below DPC level on walls..




Except that I'm not sure if the plastic is the DPC. By rights I should
have been perforating the dpc/dpm with my drilling but I didn't come
across anything.

See above. It may be bitumen.

Yes, it's a wetroom, with a shower but no bath.
Maris

I laid slates and tiles straight on the screed here. Its fine. Just use
waterproof grout. And tile up a fair way on the walls as well.

Maris coughed up some electrons that declared:

Sorry Tim I'll shut up!

Forgiven

They are on a mesh. Have to grout between all the pebbles too but I'm
thinking that that will give it the required rigidity.

Yes, it might do. The mesh will definitely give a bit of reinforcement once
buried in the flexible grout - incidentally, I would try to get the most
metally flexible grout and tile adhesive you can find for this application.
Mapei do loads of specialist products and their technical line can advice
what you need.

If I were doing this, I would do a trail run of one tile on a small offcut
of marmox on a paving slab. Then see if you can break it - bit of tap
dancing, phone a (fat) friend, that sort of thing.

Assuming the bathroom has a bath, I would most definitely put the bath on 8"
wide, thickish[1] bearer planks. The bath will go up an inch or so, but
you'll have peace of mind.

[1] Thickness depending on wood type.

Cheers

Tim

coughed up some electrons that declared:


That depends rather on the compound. I used some F Ball Stopgap 300
last weekend which really is a self-leveller, rather than a self-
smoother. Amazing stuff. Slight push with a trowel to spread it,
spiked roller, and 5 mins later it is flat and level.


Hi,

Can I ask, how thick you put it on (1mm, 2mm, 5mm?) to get that sort of self
levelling effect?

Just so I know what to expect.

Ta

Tim