Chamber under sanitary floor

In today's Elaborex blog post, Calidad en la Construcción, We explain the importance of a correct ventilation of the chamber under sanitary slab or ventilated floor.

The lack of ventilation of the chamber usually causes humidity by condensation, which in turn cause damage to the steel by oxidation which, when increasing in volume, causes the concrete to break, both in beams and joists.
According to a study promoted by the Musaat Foundation and carried out by Alberto Moreno Cansado (Head of the Building and Pathology department at Elaborex, S.L.), and Manuel Jesús Carretero Ayuso, the 5.93% of the pathologies studied were due to humidity by condensation (They can access this study here).
What's more, with the added problem that these cameras are usually not recordable, so it could be the case that it is too late when the pathology of the face in the elements of the building.

Humidity due to condensation in chamber under floor

Consequences of humidity due to condensation in chambers under slab: Oxidation / Corrosion in joist reinforcement with detachment of the covering concrete

There are many buildings in which a pair of 15-inch grilles have been left as ventilation of the chamber under the slab.×15 cm, in the best case, hoping it is enough to ventilate the chamber; and no, is not sufficient.

The Musaat foundation has prepared a series of Technical Guidance Documents on Building, including one dedicated to One-way floors with concrete joists / ribs and inter-beam, in which reference is made to this and other pathologies typical of sanitary floors.

Let's see that the current regulations CTE-DBHS1, on the point 2.2.2 Conditions of constructive solutions dice:

CTE-DBHS1, on the point 2.2.2 Conditions of constructive solutions

The truth is that, what the norm says, it's quite clear, but then, Why do we keep seeing buildings with poorly ventilated cameras?

The first thing we usually find is that this ventilation is not usually well defined in projects, when they appear, they usually only do it on budget, dedicating a game in which reference is made to a certain number of vents made of a certain material, usually 15×15 cm and without specifying where and how they should be placed. Most of the time, the section and number needed to comply with the regulations have not been calculated.

Other times it is, what's more, ventilation design issue, since the exterior terrain is above the slab, hence, to the aforementioned problem, we must add a more complicated execution that hinders the proper functioning of the ventilation.

It is also frequent, that the dividing walls of the building prevent meeting the requirement of "facing walls", causing the ventilation not to work properly.

After several years visiting construction sites and seeing the wide variety of design possibilities that can arise when it comes to ventilating the chambers under slab or ventilated slab, We could say that what is specified by the CTE-DBHS1, on the point 2.2.2 Conditions of constructive solutions, not enough to solve ventilation in all cases, owed, sometimes, design a specific ventilation that takes into account the circumstances of each particular building, that on many occasions forces us to have to consider from mechanical ventilation to a shunt ventilation system to guarantee sufficient air renewals to avoid humidity.

In Elaborex, S.L. there are technical personnel who are experts in pathologies in construction, both in building and civil works, having made more than 250 pathological studies of different kinds, since the company was founded in the 2006.

For this reason, we are aware of the importance of correctly designing and executing the ventilation of the chambers under the sanitary slab or ventilated floor..

Ask us and we can study your case, whether it is a new construction or a building already built.

-Cámara bajo forzado sanitario-.