Time Lost Due to Damp Screed: Problems with Drying in House Construction

Drops are running down the walls and our schedule is falling through. High humidity, a defective dryer, and a lack of communication are costing us nerves and money. The cause: a lack of communication between the trades. Here is exactly what happened and how things are moving forward now.

Problems with Screed Drying: Causes of Moisture in the House

In February, an important milestone was due: heating up the screed. This process prevents later cracks caused by temperature differences. The so-called "functional heating" makes the screed ready for floor covering work, as too much residual moisture in the screed can damage the flooring.

Heating the Screed: Mobile Heating Instead of a Heat Pump

The screed is heated via the underfloor heating system. Although our heat pump was already in the technical room, the site manager advised against using it. This could affect its lifespan, and full efficiency could not be achieved because the screed program requires a significantly higher flow temperature than regular operation. The alternative: a mobile electric heater connected to the flow and return of the underfloor heating.

During heating, the screed releases enormous amounts of water, which caused more than just us to break a sweat.

Condensation in the New Build: The Consequences of Missing Insulation

High humidity is normal during screed drying. Correct measures usually prevent damage. In our case, the External Thermal Insulation Composite System (WDVS) was still missing from some exterior walls at that time. This caused condensation. The warm, moist indoor air condensed on the cold surfaces of the uninsulated exterior walls. Hundreds of water droplets formed on the concrete ceilings and the interior plaster.

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At this point at the latest, dehumidifiers should have been used to protect the building from moisture and mold. But initially, very little happened.

Communication Problems on the Construction Site

Lack of coordination, unclear responsibilities, and we, the builders, were told nothing. Even during our first visit to the construction site after the drying started, the humidity was at almost 100 percent. The painter had set up construction dryers, but a week later, there was no change.

After pointing this out to the site manager, everything was supposed to change. But during our next visit, the situation remained the same: the containers of the dehumidifiers were empty and the walls were wet.

The construction site is about an hour away from our current residence and our architects' office. To ensure someone is regularly on-site and keeps an overview, the architectural office hired an external site manager. This worked well. Until now.

Missing Power and a Defective Construction Dryer

Initially, there were discussions about the power supply. The cables from the construction power box led through the front door into the interior. They would have had to be plugged in every day. Because of low temperatures in winter, no one was working there, and there was no one entering the house.

The simple solution: lead the power cable permanently into the house through a window. We first had to convince the site manager of this idea. Finally, there was power. But who empties the collection containers of the construction dryers? No one felt responsible. With a seven-liter canister, the amount of water removed from the air remained manageable. The second dryer did not work at all.

Again, it required our inquiry: Why don't the construction dryers drain the water directly through the drain? After a clear complaint, the defective dryer was replaced, and the devices were connected directly to the drain with hoses. The humidity dropped rapidly within a few days.

We observed the situation for too long in the hope that our hints would be sufficient for those involved to solve the problem. Our most important insight from this phase: escalate faster.

Frost Damage to Interior Plaster: Plaster Flaking due to Condensation

The persistent high humidity in the house caused damage. On some interior walls, the condensation froze before the heating phase began. This led to local plaster flaking. Our interior plasterer fixed the damage by sanding it down and applying a new layer of Multi-Finish.

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Conclusion on Screed Drying: Time Loss and Unnecessary Power Costs

Without ventilation or construction dryers, moisture cannot escape from the building. The consequences for our project:

• Damage to the plaster: Initially, damage caused by freezing, which was quickly repaired by our interior plasterer; later, a "sinter layer" formed on some walls, which the painter then had to sand down over a large area.
• Construction delay: The schedule shifted by at least two weeks. Due to the delayed start of the interior work, painters, tile layers, and parquet layers sometimes already had other jobs planned and had to postpone their work for us once again.
• Additional costs: The mobile electric heater ran longer than planned without drying success. This increased electricity costs unnecessarily. The construction dryers did not run for a long time but cost us rent. At least we did not have to pay the additional rent for the dehumidifiers.

Anyone who is working full-time and cannot open windows a few times a day, or empty water containers daily needs functioning coordination on-site. If something doesn't go according to plan, you shouldn't wait; instead of polite hints, give clear instructions.

Total Costs of Screed Heating and Drying