70MM SUB SCREED

Discussion in 'Subfloor Preparation' started by ROBSCOTT, Aug 22, 2016.

  1. ROBSCOTT

    ROBSCOTT Well-Known Member

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    Hi All

    I have a project on a new build for a school ,the builders had told me that the screed 70mm was pumped in which in fact is a fast set . Allowing flooring to be laid after 7 days in correct conditions . Both the builders and screeds are established firms . I placed Hydrometers in three separate positions all calibrated after 5 days reading of 98 last week 98 today 97 .
    I have now been assured that the screed laid is fast track but both the builders and screeding firm but that you can not use Hydro meters to test for damp on this type of screed . The other option i know of would be to probe test the screed. Any of you guys come across this or is someone trying their luck with me .

    Thanks
     
  2. Spacey

    Spacey Super Moderator Staff Member

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    Is it Tarmac Top flow by any chance? If it is its anhydride
     
    Last edited: Aug 23, 2016
  3. J d clarkson flooring

    J d clarkson flooring Well-Known Member

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    Like spacey says I suspect a calcium sulphate sub floor here...... Gypsum based and will cause you pain in the long run if not prepared correctly....... It is correct that it is fast track and will cure in 7 days....... The problem here is cured is not dry. If there is an ufh system then once fully commissioned the sub flor should be dry.... This will take 28 days on top of the 7. If there is no ufh then it will dry at the same rate as traditional sand/cement screed....... If they say it's sand/cement then 70mm is not thick enough to bond and will eventually break away.
    If it is gypsum based then get the heating commissioned and do a hydro test once heating is off 28 days later. Following this remove all surface laitence and STRICTLY FOLLOW the guidelines set by manufacturers of the levelling compound........ Don't throw cheap shit on it we used forbo eurocol on our last project and Ardex n/a on the one before. Any doubt both these companies offer a free site visit.
     
  4. ROBSCOTT

    ROBSCOTT Well-Known Member

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    Hi sorry for the late reply .Isocrete K screed is the material used.
    I spoken with F ball and others they all assured me the Hydro meter is fine to use and as i expected as you have pointed out cured is not dry .
    Im forbo approved so happy to use their materials
     
  5. J d clarkson flooring

    J d clarkson flooring Well-Known Member

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    Well get the reading...... I'm sure a site visit by the eurocol rep won't be an issue..... Probable route will be surface dpm/moisture suppressant then screed. If it's rough maybe prime then pre smooth before dpm. They will advise if any latency needs removing etc.
     
  6. Spacey

    Spacey Super Moderator Staff Member

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    Don't DPM it wait until it's completely dry to be safe or the easiest less risky option just walk away
     
  7. pf flooring

    pf flooring Well-Known Member

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    IS there a dpm suitable for anhydrite? was under the impression you couldnt dpm the stuff
     
  8. J d clarkson flooring

    J d clarkson flooring Well-Known Member

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    K screed is a cement based product not calcium sulphate spacey....... Or as far as I'm aware..... If it's not dry and it's a fast track installation his client may not want to wait for it to dry...... If it is cement based and his chosen subfloor preparation products rep confirms this with a site visit then it will require a suppressant or wait to fall below 75% RH which on a 70mm slab will be around 3 -4 months.
    M
     
  9. J d clarkson flooring

    J d clarkson flooring Well-Known Member

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    Correct a dpm/suppressant shouldn't be required on a commissioned anhydride floor. But k screed is cement based
     
  10. Spacey

    Spacey Super Moderator Staff Member

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    Is isocrete k screed cement bases by any chance :eek::eek::eek:
     
  11. ROBSCOTT

    ROBSCOTT Well-Known Member

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    Hi i am awaiting the data sheet I Have printed off one from their site so just want to compare . Again no way im installing the floor at presents hydro meter reading 97 which is fine as i expect it to take around 3 months to dry . Its more the fact im sure the client is trying to pull a fast one tellingme that Hydro meters are no good ?. Its a cement base product yes that is supposed to take a floor covering after 7 days . but this is still reading way above
     
  12. J d clarkson flooring

    J d clarkson flooring Well-Known Member

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    Flooring can be installed after 7 days if the correct preparation is carried out. Likely route dpm 1 coat from Ardex which will go to 97rh or 2 coat system from others
     
  13. AngryAndy

    AngryAndy Well-Known Member

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    I would believe the readings I'm getting rather than a client who would have me in court as quick as a flash!
     
  14. ROBSCOTT

    ROBSCOTT Well-Known Member

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    Yes agreed I just thought it was funny to get a call saying i cant use hydro reading and that the screeders will come down and show me how to take a reading ???. I just was wondering if you guys have ever heard that hydro meters cant be used on fast track .
    again no way my company will install or put our rep on the line if we are not happy with results .
     
  15. J d clarkson flooring

    J d clarkson flooring Well-Known Member

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    I had the same issue on a job with 300m2 of expona going onto anhydride. Screed contractor insisted it was dry my meter said 88%. I said can't dpm on anhydride or lay on a wet floor..... Heating wasn't commissioned and another contractor fit onto it and it popped clean off the floor. Meters don't lie!!!!!! Builders and screeders do
     
  16. Neilydun

    Neilydun Well-Known Member

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    I have had this. Screeded used Tomcem or similar.
    It was a concrete screed, with 7 day drying time. I was not convinced, and took my own readings, but when I spoke to the screeder, he said it could only be measured by carbide bomb test.
    I have since fitted over this many times, and never had a failure. They use it to form falls in showers, on fast track builds we do in gyms.
     
  17. Freeley

    Freeley Well-Known Member

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    Not relevant to the OP but uzin now have a system that allows you to dpm anhydrite upto 90%RH when on UFH, I'm using it on a 300sm job at the moment.
    Comprises 2 coats of 425 epoxy primer, 2 coats of 414 resin dpm, 280 primer then levelling compound, so a faith bit of work involved but gets over the problem.
    They've got the system on their website

    Sent from my Galaxy S6
     
  18. ROBSCOTT

    ROBSCOTT Well-Known Member

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    Thanks i will await the site visit and update you all on the out come .
     
  19. ROBSCOTT

    ROBSCOTT Well-Known Member

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    Well i pulled the plug on the job today was not happy with the results of the site . Thanks again for the above answers and advise
     

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