Inexpensive and non-polluting home waterproofing for roofs

How I never tire of saying that our grandparents were organic and today I come to save the alujaa method to waterproof your concrete roof with inexpensive materials and low environmental impact, in addition to being economical, this old system for roofs is much more respectful of the environment than those sold on the market.

Homemade waterproofing for roofs, inexpensive and non-polluting 1


What is Aluja, the natural waterproofing of roofs?

The Aluja is a method that appeared in Italy in the 17th century, at that time the women went up to the roof where they washed their clothes with soap and alum.

A group of architects observed that these poor houses did not have terracotta or wood tile roofs, the only known ways to adequately waterproof a roof, however, they had no leaks in their houses, so they discovered that the mixture of water and soap with the alum drying on the ceilings day after day sealed the cracks with the solid residue of a flexible and water-repellent material, the aluja was born.

How to prepare natural waterproofing.

In a drum of about 100 liters, it can be those made of sheet metal or plastic; four kilos of white laundry soap are dissolved, the usual soap bar which is made of oil or other fat, you can also make your own soap with the oil used for this and 20 kilos of stone alum.

The soap is best cut into small pieces or even grated, then the best option is to let the mixture sit in the container for 24 hours, this way the soap and alum dissolve and integrate into one solution. The ideal is to download all the materials and prepare them on the same roof.

After 24 hours, stir vigorously and check that the mixture has a viscous appearance and, just as importantly, that there is no precipitated material at the bottom, i.e. everything must be well mixed. and integrated. If not, we have to remove it and let it rest until it is as described, then we will have Aluja ready to use. Fundamental: that the Aluja remains in the form of viscous liquid before using it.

Alum, which is a hydrated aluminum potassium sulphate, is available as whitish stones in multi-kilogram bags, at major hardware or local pool maintenance stores, pharmacies, and some stores , it can be obtained.

How artisanal and ecological waterproofing is applied.

First, gather the gear, gloves, buckets, and brooms. The surface to be waterproofed must be clean, dry and without traces of other waterproofing agents. It is recommended to carry out this operation every year before the rainy season, on very sunny days to be more effective.

Once the roof is clean we wet it and let it drip, once this is done we start pouring the aluja, our homemade waterproofing with cubes on the surface and spread it with the broom, we will use gloves all along the process, because alum is a reagent that can damage our skin.

It is left for a while until it begins to dry and the second layer is applied, with this we obtain a lasting waterproofing, if it rains between the first layer and the second we have to start the waterproofing again from the beginning.

A 100 liter can gives 150 m² in a single coat, it is recommended to give two coats, and the duration is two years, but its application is generally recommended every year.

In addition to using gloves, it is advisable to go with clothes that cover our skin and goggles, since the splashes can damage our skin due to the high concentration of alum in the mixture.


Some readers have told me that quicklime can also be added to the mix, something like 20 kilos and this will make the aluja more resistant, it will also leave the roof white, which refracts the sun’s rays and keeps the house more cool, so it’s ideal for areas with high sun exposure like Mexico.

Another method with oil and lime

In this method, used car oil is mixed, which is normally delivered to you at any workshop dedicated to changing it.

What is done is take a few liters or the amount we want to prepare, and we add powdered lime, quicklime until it has a thick consistency, the good thing about this waterproofing house is that it is ideal when there are cracks, for example, because it is very elastic and quite resistant.

I leave you a video where this method is shown in more detail.

Homemade, cheap and green waterproofing.

This waterproofing material, used for centuries, has several advantages: a low carbon footprint, little transport, since we prepare it at home, it is very easy to apply on its own, all its elements are biodegradable and do not pollute too much when manufacturing or obtaining them compared to commercial products which are mostly derived from petroleum.

It’s effective, it lasts just long, it applies quickly with precautions, you can even involve children or friends in the task. I hope you find this information useful and you are encouraged to try Aluja, a centuries-old waterproofing agent. efficiency.

Leave a Comment