What Causes Damp Patches on the Concrete Floor?

What Causes Damp Patches on the Concrete Floor?

10th February, 2023

Are there damp patches showing through onto the surface of your concrete floor? Is there evidence of underlying moisture through soaked carpets to wooden floor tiles warping?

One of five things causes this issue:

  1. No damp proof membrane was used in the construction of the foundations and floor layers before the concrete was laid.
  2. The damp proof membrane was not adequate for the job.
  3. No resinous floor coating was used.
  4. An incorrectly mixed batch of cement, or that is not cured, and holding moisture in.
  5. The soil beneath the concrete does not retain water away from the surface.

These problems can occur in any location and could be brand new or very old. Dampness in a house can be picked up by a pre purchase survey or an independent damp survey.

In most cases, industrial, commercial, and residential buildings are erected on top of soil that has been specially prepared. Concrete covering the soil is known as slab-on-grade. Manufacturers of flooring products indicate the maximum moisture that can be contained in the concrete layer. Regardless of what type of floor covering is used, e.g., carpet, linoleum, wood, or carpet tiles, they have tested specifications for the concrete moisture volume ceiling required to fit their product without warping, pulling up, or becoming damp.

The Presence of Moisture in a Concrete Floor

Moisture vapor transmission (MVT) refers to a process whereby moisture travels by osmosis from the damp ground into the concrete, which is naturally permeable. Even after curing, a concrete slab will continue to release moisture from its surface. Concrete will never be totally moisture-free.

Producers of flooring recommend that tests be carried out by a damp specialist London. The first test measures the concrete’s relative humidity (RH). An alternate method of calculating the moisture in concrete is the rate at which vapor travels through the concrete. Manufacturers have solutions, such as rising damp treatment and condensation treatment to offset MVT.

Risks of Moisture Vapor Transmission (MVT)

Moisture vapor transmission that exceeds recommended limits can give rise to problems, such as:

  • The flooring product may undergo delamination, or the separation of horizontal layers from each other.
  • Alternatively, the two surfaces will fail to adhere to one another, due to the condensate being extremely alkaline.
  • Bubbling may be visible, and cracks may develop in the concrete, allowing more moisture through.
  • The elderly is especially at risk of taking a nasty tumble when attempting to navigate uneven surfaces.
  • However, any person may find themselves tripped up and injured – this could lead to injured on duty (IOD) or civil claims.
  • The flooring will look ugly and unprofessional.
  • The lifespan of flooring products is decreased.
  • A warranty may become invalid if MVT requirements are not met; hence, the owner will have to replace the flooring at his/her own expense.
  • The concrete slab will eventually wear down completely.
  • This could also encourage the growth of mould or the proliferation of pathogens.
  • Repairs are costly and result in unscheduled downtime and loss of productivity. In the home, this can be inconvenient.

Repairing the floor after an MVT failure may require the whole concrete slab to be replaced with a slab that complies with MVT. All pests and mould will have to be eradicated. The damaged flooring product will have to be removed and disposed of. MVT solutions will be used before replacing the flooring with undamaged products. All of these costs add up quite substantially.

Becoming Aware of Moisture in Concrete

The condition of flooring must be inspected on a regular basis in conjunction with the company’s health and safety checklists. Catching the problem early will prevent excessive damage or danger to life and limb. Signs may not be readily apparent in the beginning. This is what you should check for:

  • Discolorations that are darker than the surrounding areas and any damp places on the carpet or tiles.
  • Delamination.
  • Floor tiles that are loose and lifting up or grout that is coming apart.
  • Areas of bubbling or cracking.
  • Condensed moisture leaving behind a salt coating on the floor surface that is very alkaline.
  • Signs of mould – a smell of mildew or an overall musty odour, or black mould stains on floors, walls, and ceilings.

If you follow this checklist and have a positive finding (answer in the affirmative), you should have moisture vapor testing done. A professional on London damp surveys can make this judgment for you by conducting one of several tests that measure moisture in concrete floors, and advise on steps to resolve the problem, or undertake the repairs.

Best Time(s) to Check for Moisture in Concrete Flooring Slabs

It would be great if every concrete slab was subjected to an MVT test before being used in the construction of flooring. In reality, this does not happen. Nevertheless, all concrete slabs should ideally be tested once cured and again before being covered with tiles, wood, or carpets.

An Alternate Explanation – A Leaking Pipe

A leak can form in a pipe if it is frozen in cold weather. Cold water tanks in attics sometimes fail to switch off after filling up. This happens as they age. If the pressure in a boiler drops drastically, this could also indicate a leak in a pipe. Any one of these problems may cause moisture to build up in walls and ceilings without being noticed and find its way into the concrete floor. Professional assistance is needed to find the leak.

Damp in Concrete Floors due to Landscaping

Concrete is porous, meaning that it readily accepts and holds moisture. This moisture rises from the soil beneath the concrete slab. It then affects the floor covering that has been attached to it.

By simply removing a big tree or several bushes, excess, unused water remains in the ground. It raises the level of ground water and penetrates concrete slabs that are the first layer when installing flooring. Get a professional to assess your concrete slabs for moisture content and to advise which plants can be removed safely. A professional on damp proofing London will remove the current concrete slab, install a damp proof membrane (DPM) over the soil, and put the concrete slab back on top of the DPM.

The ground is covered by earth with a hard core of soil over it. A damp proof membrane is placed over this. The next layer may consist of insulation. Thereafter, the concrete slab is placed in position. Now the flooring surface is ready for the installation of tiles or carpets with no danger of moisture causing the problems we have looked at.