Techniques for speeding up screed drying

[Paene Finitur]

Does anyone know of any tried and trusted techniques for speeding up drying of a basic concrete screed? Here's the context: I have a tanked basement with a Delta pumping system. A base screed has been placed over the floor membrane with the insulation, underfloor heating and top screed still to be done.

 

We've got a temporary pump operating as the electrics have not yet been connected. Up to end of December the screed was drying out nicely although certain areas were concerning me and potentially indicated that the membrane might have some small leaks that needed to be addressed. The contractor was due to look at these after Christmas, but on Boxing Day, the pump faulted and we had a flood - back to square one and the contractor wasn't able to identify any leak areas as the whole of the screed was no damp. We dried it as much as we could and a month later were due to get the contractor back. Two days before they were due to come, a builder switched the pump off overnight in error and the basement flooded again. We've wet vacced it out, but I understand it takes around a month per inch of screed for it to fully dry so it's still pretty damp.

 

We've since had the contractor in again to look at some wall issues and he suggested heating the basement to help dry it out. I've tried using a diesel heater, but it's very localised heat (the basement is roughly 9m x 6m) and doesn't appear to make a huge amount of difference. Smaller but electric powered heaters might cover the area better, but until we get the electric supply in, the power needed is going to be too great for the existing power extensions. That won't happen for another week or so. Also, there is going to be an air ventilation system based on a Mitsubishi Lossnay, but that won't be in action for some time yet.

 

I'm wondering whether there are any ways to draw the water out of the screed, such as sawdust, skim plater, paper etc, that I can speed up the process with as we're now two months behind with it. Any thoughts/experiences/suggestions gratefully received.

 

Thanks!

Edited March 5, 2022 by Paene Finitur
Typos and little changes

[TonyT]

Get some air blowers in blowing air, circulating air from the basement outside, crack open windows,  etc 

 

buy a humidity meter so you can monitor results 

[tonyshouse]

Open the windows!

[Mr Punter]

That sounds like a fatally flawed basement design.  Is it the case that if you ever have a power outage it will flood?

 

For drying I also like open windows, but if you cannot get much natural ventilation a combination of dehumidifiers and heaters works well.  We had a flooded new build due to a leak at first floor which pissed in overnight so it was like a rainforest on the ground floor.  2 big heaters, 2 big dehumidifiers on 24 x 7 and 2 weeks later it was dry.  We didn't even need to replace the ceilings, just a re-dec.

[Nickfromwales]

5 hours ago, Paene Finitur said:

We've wet vacced it out, but I understand it takes around a month per inch of screed for it to fully dry so it's still pretty damp.

You are confusing curing times with how long a cured screed would dry out if it got wet after curing   

A cured screed won’t absorb the moisture as much as you think it will / has, so the issue will be the trapped water between the layers / membranes / Insulaton etc where water will sit and have to be extracted through forced ( mechanical ) ventilation / dehumidification.

As stated, metering and monitoring will be your only means of measuring success.

 

Sounds like a pita of a basement to look after. What height did the water get to above the top of the screed? 

Edited March 5, 2022 by Nickfromwales

[Paene Finitur]

30 minutes ago, Mr Punter said:

That sounds like a fatally flawed basement design.

Thanks - that helps! 🙂

Quote

Is it the case that if you ever have a power outage it will flood?

There are three pumps (2 x groundwater and 1 x foul) all on different breakers and backed up by UPS. The pumps are alarmed and linked to a monitoring centre so if both groundwater pumps give up, there will be a call out.

Quote

For drying I also like open windows, but if you cannot get much natural ventilation a combination of dehumidifiers and heaters works well. 

Yes, well, as you might have guessed this is entirely subterranean, so there are no windows. I will go down the heaters/de-humidifiers route but can't do that until the supply is completely in (the pumps are on a temporary supply at the moment, which is vulnerable - thus the floods.)

Edited March 5, 2022 by Paene Finitur

[Mr Punter]

4 minutes ago, Paene Finitur said:

There are three pumps (2 x groundwater and 1 x foul) all on different breakers and backed up by UPS. The pumps are alarmed and linked to a monitoring centre so if both groundwater pumps give up, there will be a call out.

 

Sadly not idiot builder proof!  Was the UPS commissioned as I would expect the battery to last at least a week.

 

Basement waterproofing with a high water table is no mean feat.  Internal drained membrane and pumps is the lowest risk system so hopefully you won't have any further issues other that the maintenance costs.

[Paene Finitur]

4 minutes ago, Nickfromwales said:

You are confusing curing times with how long a cured screed would dry out if it got wet after curing   

A cured screed won’t absorb the moisture as may have as you think it will / has, so the issue will be the trapped water between the layers / membranes / insulation etc where water will sit and have to be extracted through forced ( mechanical ) ventilation / dehumidification.

As stated, metering and monitoring will be your only means of measuring success.

 

Sounds like a pita of a basement to look after. What height did the water get to above the top of the screed? 

Thanks, there have been quite a few groundwater issues mainly because the exterior landscaping, hard-standing and drainage is still being sorted out. They are also iteratively dealing with issues with the membrane - I expected that might be the case.

 

Each flood hasn't gone more than two inches or so which is bad, but not so bad as it could be. when it was open to the elements, four feet deep floods were not uncommon! We had a terrific deluge the other week with the storms and the pumps coped admirably. Not looking forward to the electricity bill though!

[Nickfromwales]

1 hour ago, Paene Finitur said:

Thanks, there have been quite a few groundwater issues mainly because the exterior landscaping, hard-standing and drainage is still being sorted out. They are also iteratively dealing with issues with the membrane - I expected that might be the case.

 

Each flood hasn't gone more than two inches or so which is bad, but not so bad as it could be. when it was open to the elements, four feet deep floods were not uncommon! We had a terrific deluge the other week with the storms and the pumps coped admirably. Not looking forward to the electricity bill though!

Ok, not great, could be worse.   

I assume you’ve got solar PV to offset the known constant electric consumption? Would be a no brainer for you as you’ll be using your excess without a doubt eg 100% self consumption would be feasible.