small damp patch. is dpm necessary? + walking on f-ball 700

[mac391]

Mattysupra

If you read my earlier posts you will see the advice i gave was correct as far as i know an understand..

I didn't recommend using the wrong products as you suggest, i just read into what i thought was someone with little time and advised accordingly.

I fully understood he used a damp meter and not a hygrometer (read the previous) and made it clear that puncturing a liquid DPM would render it as useless.

There is a graph you can use that relates simple moisture meter readings with RH (relative humidity). A moisture reading of 5% = an RH of 25% and a reading of 15% = an RH of 75%, so his reading of 10% = an RH of 50%. None of which is totally accurate, more a rule of thumb. As the DPM was already laid and he wanted to lay ply, a 50% RH (although estimated) was within guidelines and therefore the DPM was unecessary and safe to puncture with screws to fix ply. 700 flex, a great product but expensive, was also unecessary.

Also, it is definately possible to achieve an RH of a concrete slab of less than 10% considering dewpoint, temperature and correct callibration. Read up on EMC (equillibrium moisture content)

Total respect matty, were all still learning !!

 

[mattysupra]

can you post up the graph you talk about that converts moister reading from 10% or what ever it is to 75%RH for me please?

also can you post up your findings of how it is possible to get 10%rh in a normal domestic property for me also ?


we are all still learning as you say and i would like to see the above if it is true?

 

[rangorgubbins]

Do you know of any alternatives to f-ball 700 flex? The local supplier around here is not all that local. Idealy something that i can get from one of the large sheds. Preferably cheaper than the f-ball product too!

I've almost finished fixing the ply sheets down. 95% of the floor is now smooth and level, but there are a couple of joins where there is 2-3mm gap between the plywood sheets, and a height difference of 1-2mm. Do i need to smooth this? or will the tile adhesive sort this out?

Cheers!

p.s. i glued the small area of concrete to the ply using no-more nails ultra. As long as it holds down for a week or two, by then it will all be covered in kitchen units the weight of which should hold everything in place. Not the most professional method perhaps, but then i'm not a professional

 

[mattysupra]

uzin 175 is another product. however not many places stock it.

You can use a product called skimcoat to go over the joins but as your putting ceramics down you will loose this in the adhesive.


As you have put down plywood all over, what are you using the flex compound for? Is it for the height difference between the two floors?


did you look at the link i put up a few posts back? There are pics and instruction on there.

 

[rangorgubbins]

hi matty,

yes i read the link. A nice guide! Cheers.
I was thinking of putting flex down to make sure the floor is completetly level and smooth for the tiles.
I have laid sheets of ply down over the floor boards and concrete, but there are a couple of small (1-2mm gaps) between some of the sheets of ply, and also in a couple of areas there is a height difference between the sheets of ply (again only 1-2 mm). However these areas will have kitchen units over them, so I think i'll just tile over and not worry about using any flex compound.

 

[mattysupra]

ye, i dont think you need to use the flex for a few mm with ceramics.

if you was installing karndean/amtico etc then i would consider using skimcoat.

However you dont need to.

Good luck with your tiling