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joe90

Will my floor dry this weather?

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I had a liquid screed laid a few weeks ago and was told it dried at 1mm per day, so 60 days. The weather ( especially down here) is just permenantly damp and the floor “appears” to not be drying. Does this stuff dry chemically or do I have to put heat in the house?. Whenever there is any wind I open up all the doors and windows but mostly it’s just very still and damp. ( I am loathed to spend money on electricity to heat a building site!).

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From what I understand you do need conditions that will allow moisture to be removed. Heat and airflow are the 2 main contributors to this.

 

In our case I switched on the MVHR early and put it on a timer so that when people were working in the house it would be off (to avoid too much dust in the works, so i asked the builders to open windows and doors during the day and shut them all when they left), then come on overnight for approx 14hrs. I also used a large fan and heater in our basement as that was very damp from flooding during some core drilling through the ICF.

 

I then changed the filters and washed the heat exchanger prior to moving in - they were filthy, and I think we still have a bit of dust in the ducts but we live with it.

 

In all it took a bit longer than the 6-8 weeks (calculated) it should have to get a sensible reading on the meter.

 

Also, suggest you scrape off the laitance sooner rather than later. It will be easier do remove if done early and will also improve drying. Tip from my screed company.

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Thanks, yes I scrubbed the floor soon after laying which got it smoother, I have got a “ damp meter” for testing firewood, will that do and what “ dampness/dryness” do I need to achieve before laying flooring ( tiles and wood)?

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1 hour ago, joe90 said:

I had a liquid screed laid a few weeks ago and was told it dried at 1mm per day, so 60 days. The weather ( especially down here) is just permenantly damp and the floor “appears” to not be drying. Does this stuff dry chemically or do I have to put heat in the house?. Whenever there is any wind I open up all the doors and windows but mostly it’s just very still and damp. ( I am loathed to spend money on electricity to heat a building site!).

The 1mm per day for drying is a rule of thumb and only really applies for thin screeds (like yours) and where you are drying the screed in ideal climatic conditions ie summer. In winter its a different matter.

 

The rate of drying of the screed depends on there being a good differential between the relative humidity of the screed and that of the air that you are using to attempt to dry it. In summer that works well but in winter, unless you have heating available, the relative humidity of the air will be very similar to your screed and its not going to dry out to the required 75%.

 

 

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@joe90

Testing.

The target is 75% RH

 

Air Hygrometer Test: This is the only method recommended by the British Standards. This involves the measurement of the moisture released by the screed into a sealed area over a time span of 72 hours (this is to reach equilibrium with concrete substrate). An accurately calibrated hygrometer is placed on the screeded floor and sealed for the prescribed time. The reading obtained shows the humidity in the sealed area, from which the moisture content is calculated. This is the traditional method and is not very widely used these days as the procedure is quite time consuming.

Concrete Moisture Test (CM Test): This is a method that yields speedy and accurate results and is preferred by most specialist screed manufacturers.

There are currently 2 methods followed for CM tests- destructive (Calcium Carbide test) and non-destructive (Tramex meter test)

  • Calcium Carbide Test: A mid depth sample of the screed is taken and allowed to react with calcium carbide reagent. Upon reacting, the mixture releases acetylene gas, the amount of which indicates the level of moisture in the sample.
  • Tramex meter: This is a more convenient method and is also accurate and speedy. The Tramex meter is an easy to use electronic device which can provide various measurement results. After choosing the CM measurement option from the menu, the meter simply needs to be put against the screeded surface to get the moisture content displayed in %.

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Cut a small piece of polythene, a  ft sq, and put it over the floor. Let it sit for a few hrs and lift it and see how much moisture is underneath. Then you will know if it's drying out any at all.

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I used an old fashioned air hygrometer purchased off eBay. It can be calibrated on site using salt water, then selaed on to the floor and left for a day or two to stabilise.

 

@Ian is right in that you need to reduce humidity in the room to achieve drying. Heat helps in that it redices the relative humidity in the air, but you must extract that moist air else you risk it condensing and you have not gone forward. An advantage with the MVHR method I used is that the return air is dry compared to extract air. The MVHR drain pipe was full of water for a period.

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2 hours ago, joe90 said:

( I am loathed to spend money on electricity to heat a building site!).

Really? Such an important hurdle, and only a moderate investment is required, surely a good investment if it goes towards preparing your house to be finalised and habitable?

Is your mvhr up and running ?

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1 hour ago, Nickfromwales said:

Really? Such an important hurdle, and only a moderate investment is required, surely a good investment if it goes towards preparing your house to be finalised and habitable?

Is your mvhr up and running ?

 

Yes, guilty as charged of being tight!!! ( I call it being prudent)

 

No, MVH is not up and running and mine is one of those without a condensate drain ( discussed previously and generally agreed it was ok) so I am cautious about using it in a very humid envoironment.

 

I guess I need to get some heaters in and ventilate. I have a smallish dehumidifier, is it worth hiring an industrial one to get the job done?

 

 

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If you use a dehumidifier make sure the bucket has a sealed and tight lid, else you will be trying to dry the water in the bucket. Better still hose to outside.

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1 hour ago, joe90 said:

 

Yes, guilty as charged of being tight!!! ( I call it being prudent)

 

No, MVH is not up and running and mine is one of those without a condensate drain ( discussed previously and generally agreed it was ok) so I am cautious about using it in a very humid envoironment.

 

I guess I need to get some heaters in and ventilate. I have a smallish dehumidifier, is it worth hiring an industrial one to get the job done?

 

 

Prudent.... ?

I'd say hire 2 medium sized units and place them apart if it's the whole ground floor. One will struggle due to the internal walls. 

Make the place as airtight as possible to maximise their efficiency ( plus the dehumidifiers will give off heat as a waste product too so maybe no need for heaters  ? ). 

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17 hours ago, joe90 said:

 

Yes, guilty as charged of being tight!!! ( I call it being prudent)

 

No, MVH is not up and running and mine is one of those without a condensate drain ( discussed previously and generally agreed it was ok) so I am cautious about using it in a very humid envoironment.

 

I guess I need to get some heaters in and ventilate. I have a smallish dehumidifier, is it worth hiring an industrial one to get the job done?

 

 

I do a lot of commercial floor tiling

definately don’t use heaters

All they do is push the moisture around the building. 

you can hire couple large  dehumidifiers for not a lot of money You’ll be surprised how quickly they draw the moisture out 

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Thanks guys, just messaged my builder to find out where I can hire a couple of dehumidifier,s. 

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Two dehumidifiers ordered for today to leave on over the Christmas week, £60 each. Thanks one and all ?

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8 minutes ago, joe90 said:

Two dehumidifiers ordered for today to leave on over the Christmas week, £60 each. Thanks one and all ?

Quite satisfying emptying those buckets of water out each morning

Im sure you will see a massive difference in a week ? 

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1 minute ago, nod said:

Quite satisfying emptying those buckets of water out each morning

 

My builders just fed the outflow directly into the drain so no worry about emptying buckets.

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2 hours ago, le-cerveau said:

My builders just fed the outflow directly into the drain so no worry about emptying buckets.

Deffo the only way if your not on site every day for that week @joe90

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They have been running fir about 4 hours and collected about 1 gallon of water so far. I am on site every day so emptying containers is not a problem, it also gives me chance to monitor how much water is removed each day. As it’s Christmas and the hire company are moving premises they have let me have them for two weeks for the price of one, not sure I will need them that long. I will report back.

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34 minutes ago, Ian said:

@joe90

Btw do you have underfloor heating?

 

Yes Ian, my builder and the liquid screed layer told me the floor dries at 1mm per day (60mm) but this assumes it is actually drying ( I.e. not in damp deepest Devon in winter) and the UFH should not be used till it is fully dry and even then in small doses at low temps. My pressure is getting the tiling and wooden floors down asap.

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@joe90

if your u/floor heating is working I’d explore your options for using it help to force dry your screed. I’ve read that it’s possible but it’s not something I’ve any personal experience of.

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@joe90

How did you decided to have a 60mm screed depth? rather than a thinner screed (cheaper) that is still possible

Would you have gone deeper than 60mm for any reason if cost was not issue ?

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14 minutes ago, Lin said:

@joe90

How did you decided to have a 60mm screed depth? rather than a thinner screed (cheaper) that is still possible

Would you have gone deeper than 60mm for any reason if cost was not issue ?

 

Originally I was going to have the UFH within the 100mm concrete slab but due to Ill health and short timescales I had to settle for liquid screed laid afterwards and as our house is heavy weight I wanted the thickest screed I could to even out temp swings. I was informed 60mm is the thickest they recommend.

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