Damp Cellar: How to Solve the Problem

Having a damp basement is more a rule than an exception.

Bottles of wine in a damp cellar

Since cellars are, by definition, basement rooms, it is more than natural for a high degree of humidity to occur inside them.

Is having a damp cellar a problem?

Very often it is taken for granted that it is, but actually having a damp basement becomes a problem in relation to our use of the basement.

If we store materials in the basement that we generally do not use in the house, then moisture is a problem.

Just think about placing electro-tools in the cellar (if we do not have a well-organized garage): in the presence of moisture they would inexorably tend to deteriorate.

If in the cellar, on the other hand, we place cold cuts and wine bottles, here is that a certain degree of humidity is not only not detrimental but, on the contrary, proves ideal.

Before thinking about complex and costly interventions, therefore, it is worth considering the possibility of changing the "intended use" of our cellar, placing there only things that are not affected by moisture.

In general, the causes of the presence of water in the basement should be sought outside.

Even if the ground surrounding the foundation has good drainage, in fact, all it takes is a crack in the cellar masonry for water to seep in, all the more so if insulation sheathing has not been put on the outside.

Many interventions can be done from the inside, but in certain circumstances, only intervention on the outside can really prove decisive.

If the basement is more humid than wet

If the basement is more damp than wet, this may be caused by stagnant water vapor produced by any appliances present, of which the washing machine and dryers are among the most damaging.

The dryer exhaust for laundry should definitely vent to the outside.

Keep in mind that certain heating systems, such as gas or oil stoves, also produce water vapor, and while they dry on the one hand, they also further humidify the room.

Another very common cause of high humidity in the basement is rising damp, through the walls and through the floor.

It follows that, in order to eliminate any problem of moisture from outside, the cellar should be perfectly insulated, that is, it should be a kind of box packed on all sides.

Proper ventilation of the cellar room is determined to prevent the accumulation of moisture, so there should be at least vents or small windows that allow moisture to escape to the outside.

Basement doors should also never be sealed but, if possible, should be made of aluminum or plastic (materials that are poorly attacked by moisture) and should always have ventilation holes, bottom and top, to allow air to recirculate.

In extreme cases, heat-recovery electric system or electric dehumidifiers should be used.

Keep in mind that seepage through walls and floors drags water and moisture with it.

Sometimes the moist air generated inside the cellar condenses on contact with wall surfaces, giving the impression that moisture has penetrated from outside.

Another problem that invariably occurs when there is excess moisture in rooms is mold on the walls; we have already discussed how to combat mold in another article.

How to check whether the moisture is coming from outside or inside

To detect whether the problem originates from inside or outside (and whether ventilation may be a sufficient remedy), you can do the test I am going to describe.

You must tape a sheet of heavy plastic, a square about 40 centimeters on a side, to the wall below ground level and leave it in place for several days.

If moisture forms under the plastic, it means that water is seeping, by capillarity, through the grains of sand and cement in the masonry.

If, on the other hand, the surface of the plastic remains dry, and the surrounding wall appears damp, then it means that the water comes from condensation of moisture present inside the cellar.

Damp cellar solutions

There are various ways of plugging up infiltration: if the wall is not too damp, it can be made waterproof with a layer of hydrophobic cement paint, with three coats of bitumen emulsion, or by plastering the wall on the inside, with mortar made with one part Portland-type cement and three parts sand, with the addition of a waterproofing additive (silicone or synthetic latex) in the proportions indicated in the instructions.

Today there are also restorative plasters that, due to their grain size, do not block moisture but, on the contrary, allow the plaster to breathe and not get wet.

Of course, this assumes that, to be effective, there is necessary air circulation within the room.

However, if you want to make the basement habitable, the third solution (a coating with gypsum board) will only protect the subsequent finishes, but will not solve the problem, unless the moisture is very modest.

In any case, the cladding must be anchored to an aluminum frame and also the insulation material inserted in the cavity must never come into contact with the damp wall.

A truly effective solution for large-scale seepage is to waterproof the outer surface of the walls with tar, but since excavation is required, this is a job that should be entrusted to a specialized contractor.

Another cause of seepage is a deteriorated floor, in which case it should be covered.

If you use the basement occasionally, a sheet of polyethylene may suffice, but if you use it often, it will be necessary to lay a concrete covering.

If, however, we do not want to totally block the moisture but, on the contrary, exploit it, we could remove the floor and, after creating a sand slab, lay a dry brick lining.

Our damp cellar will turn into the ideal environment where we can hang sausages or store wine.


Always remember that water, especially if it seeps in from the outside, is very difficult to stop.

Even by making an external excavation and then waterproofing the wall, it could seep underneath it and re-emerge from the floor.

The only solution, then, is both to insulate the wall but also to find a way to channel the water elsewhere.

When this is not possible, we try to make moisture our friend, perhaps using it to create a cool cellar in which to store foodstuffs and wines.