Yet another screed drying question - Tile Advice

[On one]

Hi All
I have been to see a job last week,90m2 ground floor kitchen/conservatory. It will be,when it is laid, a 60mm sand/cement screed over wet ufh over insulation over a block and beam floor.
Unfortunately the lady of the house was not aware of the drying times for the screed and was expecting her dream kitchen/conservatory to be done and dusted before Christmas. I have told her want the screed and the ufh requires prior to commencing tiling,but she has come back to me with this scenario from the builder/screed company........

......2 days after the screed has been laid start the ufh heating at its lowest level for a week,then increase the heating by 1 degree per day,up to normal operating temperature.

Has anyone heard of this procedure being correct or have they got their facts slightly wrong/stretching the truth?
P.S would a screed this size require reinforcing mesh?

Thanks in advance Wrighty

 

[Ajax123]

Hi All
I have been to see a job last week,90m2 ground floor kitchen/conservatory. It will be,when it is laid, a 60mm sand/cement screed over wet ufh over insulation over a block and beam floor.
Unfortunately the lady of the house was not aware of the drying times for the screed and was expecting her dream kitchen/conservatory to be done and dusted before Christmas. I have told her want the screed and the ufh requires prior to commencing tiling,but she has come back to me with this scenario from the builder/screed company........

......2 days after the screed has been laid start the ufh heating at its lowest level for a week,then increase the heating by 1 degree per day,up to normal operating temperature.

Has anyone heard of this procedure being correct or have they got their facts slightly wrong/stretching the truth?
P.S would a screed this size require reinforcing mesh?

Thanks in advance Wrighty

How many issues can one builder pack into one screed....

Firstly depth. The minimum depth for sand cement screed laid on insulation should be 65mm. That is th minimum depth not the nominal depth. With a wet underfloor heating system this should be increased to 75 to 80mm to take account of the minimum depth which is over the top of the pipes.

90m2 should be split into bays of no more than 6m x 6m. This is the maximum recomendation based on ideal conditions and full compaction. With heating I normally suggest smaller bays typically 15 to 20m2

At 90m2 I would anticipate at least 2 independently controlled heating zones. These should be split by a full depth movement joint. There should also be joints across any door thresholds e.g. Where the kitchen meets the conservatory.

sand cement screed should be reinforced with either poly fibres or d49 steel mesh

srying time can be reduced by using water reducing additives however these should all still be cured using a polythene membrane placed over the newly installed screed for 7 days. Underfloor heating should not be switched on until the screed has achieved the tensile strength it requires to prevent thermal cracking. This is normally minimum 28days

i am not aware of any wet systems that allow the levels control required to lift the flow temperature by 1degree per day. This is normally 5 degrees per day.

failure to cure the screed and prematurely heating it will desiccate the screed and prevent full hydration of the cement leaving a potentially friable and weak screed.

if ever I saw a case for flowing screed and sensible controlled force drying this is it.... Otherwise my advice would be "run forest run"....

 

[On one]

Cheers Alan
You've just confirmed what I already thought, re,covering the screed with poly,min 28 days curing and then commissioning the heating.
Seems like someone is trying to stretch the facts to suit their needs.
I did check with Schluter about the use of Ditra,but they confirmed my suspicions that the need for UFH to be commissioned after the screed had dried meant this didn't fast track the process.

 

[On one]

Personally,I think I am just being asked to price this for ££ comparison or tech advice prior to the job being given to someone who has their feet already under the table. Hay Ho!