Humidity—warm and humid air condenses into surface moisture when it comes into contact with the cool surface of your concrete floor or slab. Faulty/Missing Vapor Barrier—moisture from the ground can seep up and through the concrete.
The easiest solution for damp proofing concrete floors is to install a plastic membrane. Essentially, this is a plastic mesh sheet specially formulated to ensure that moisture cannot penetrate. It sits between the concrete and the underlay floor covering.
The most common differentiator between rising and penetrative damp is the height at which it occurs. Rising damp will only occur up to a metre from the ground, whereas penetrating damp can occur anywhere.
Water can seep through concrete through an imbalance of relative humidity. The direction moisture moves is determined by the humidity in the concrete and air, so if the concrete has higher relative humidity than the surrounding air, it will release moisture into the air.
Concrete is by design a porous material and water can pass through it by hydrostatic pressure, water vapor gradient or capillary action. Water can also enter at cracks, structural defects or at improperly designed or installed joints.
Concrete slabs are very porous. This means standing water can easily fill in pores on the surface and eventually break down the concrete. As a result, the concrete may crack, move, or even settle.
Leaks in plumbing and central heating pipework can cause damp patches which could be misinterpreted as rising or penetrating damp. This is especially common where the pipes are run beneath a floor or are buried in wall plaster.
In practice Rising damp can generally reach the height of 1.0m above the ground level however for various reasons the damp can go higher.
General academic consensus puts the incidence of rising damp in all damp properties at around 5% but our own view based on pragmatic experience of carrying out hundreds of detailed damp investigations, using the full range of diagnostic tools puts the incidence at significantly less than 5%.
Basements and garages - the typical rooms with concrete floors - also suffer from poor air circulation, giving the moisture nowhere to go once it seeps through the floor. Sealing the concrete can help eliminate the dampness on your floor.
Concrete Moisture Test
One of the simplest, most economical test methods for determining whether there may be moisture in concrete is the ASTM D 4263 Concrete Moisture Test. Duct tape an 18-inch square piece of plastic onto the exposed concrete and leave it for 16 hours.
Although the bulk of the hydration process takes place in the hours and days immediately after the pour, concrete needs 28 days to fully dry.
There is no need for concrete to breath from the point of view of the strength of the material. There will be moisture retained from the original mix and it is possible some are confused about the chemistry of concrete and think it needs to dry, but the truth is the complete opposite of that.
Signs you may have a slab leak include:
You hear water running under your floors, but your taps and plumbing appliances are off. Carpets are damp or wet without an explanation. You smell mold, mildew, or a general mustiness. There are warm spots on your floor.
Rising damp can be a serious problem, as if left untreated it can lead to structural issues. The damage it can cause to your plaster, flooring and decorative finishes as well as the smell also makes it very unpleasant to live with.
The most common and effective way to treat rising damp is to install a remedial damp proof course by injecting a water repellent damp proof cream into the mortar bed joint of affected walls.
The only way to treat rising damp is to create a new damp-proofing course to prevent moisture movement through the structure. Historically, walls were cut into and masonry removed to install a new physical damp-proofing course along the masonry line. This process poses a number of problems for most structures.
Very simple fix to stop penetrating damp. Simply repair or unblock the gutters and downpipes. Dilapidated or Damaged Windows - Check window sills to make sure the drip grooves are not blocked as these can be susceptible to a build-up of dirt and moss. If found to be blocked, make sure to clean them thoroughly.
To stop penetrating damp affecting masonry, bricks can be treated with Stormdry Masonry Protection Cream. Stormdry is a colourless  water-repellent treatment for brick, stone, masonry and concrete.
If the water is seeping up through the floor, it could be a result of insufficiently-sealed foundations or there could be cracks in the foundation floor.
Water can ruin the exterior and interior of your home. Your foundation can be discolored, and prematurely aged. If it soaks through to your floors it can ruin hardwood, laminate, and tile… not to mention the damage to baseboards and your walls! Basements smell musty from always being damp.