Wooden houses and marches of the wall base: how to intervene

The rule of 4 d

The 4 D rule is a fundamental principle for the functionality and durability of wooden buildings, especially in environments exposed to water and humidity. It serves to prevent damage and degradation from water, the main enemy of wood. The 4 “D” are for:

• Deflection (deviation): The water must be as removed from wooden surfaces as much as possible. This means designing protruding roofs, adequate length arguments, gutters and coatings that deviate rain away from the structure;
• Drainage (drainage): The water it manages to enter must be able to be drained quickly and effectively, without accumulating or stagnating. For example, with the possibility of ventilation and the presence of empty spaces between the stratigraphies of the construction elements;
• Drying (drying): the wood must be able to dry quickly after being wet. This is achieved by promoting ventilation and choosing materials and constructive details that allow perspiration. The goal is to reduce wet time as much as possible;
• Durability (durability): The materials must be resistant to humidity and biological attacks for very long times, compatible with the life expectancy of the property. This includes the use of naturally durable or adequately treated woods, and additional protections such as paints or impregnating people.

The 4 D rule is the guide for technicians and manufacturers to avoid and for prevent marching, mold and degradation in wooden structuresthus guaranteeing an adequate useful life of exercise to the building.

As always, on the theme of building pathologies it is necessary “prevent it as possible and correct where necessary” (Marco Argiolas, building pathologist).

The marching of the wall base on wooden houses

One of the problems most encountered in wooden constructions is the marches to the support of the wall; In fact, it often happens to see buildings built about ten years ago partially or completely rot at the base.

The problem arises from the fact that the wooden walls, both in XLAM and in the frame, coming supported directly on the foundation audienceare at the same altitude of the countryside plan, making it thus impossible to protect water and humidity. Wet wood promotes the proliferation of spores, mushrooms and molds, determining a strong one marchieswith an important decrease in resistance. The objective of this short article is to bring to light the problem and describe one of the possible solutions to summary; Too vast the topic to disseminate it comprehensively in a single chapter.

I would not like to dwell in the technical-legal part, but it is a must remember that there are Technical reference standards which, for example, the DIN 68800-2-: 2012-2 where we find the basic measures to be followed in order not to make the error described as of now and from which it is easily evident that the support of the base of the wooden wall must be at least a share + 15 cm from the countryside plan. To this and other similar rules they currently also refer i Arca and Casaclima protocols who advise their respect by virtue of that durability of the building that the designer, the manager to the works and the manufacturer must guarantee.

Let’s now analyze What we should do If we were faced with a situation similar to the photo in Figure 1:

1. Careful Analysis of the state of the art through samples and carotages
2. Study of the causes and construction details
3. Study and design of structural remediation

Structural renovation passes through three fundamental passages:

1. Removal of marching and how much it bewitched
2. Creation of a Cordolo in ca act to raise the support share of the base of the wall
3. Reconstruction of the previously removed part of the wall and the thermal finishing coat

In Figure 2 We see an almost finished remediation; It can be observed, from the bottom up:

1. The new curb in ca
2. The new sleeping in larch that replaces the old and removed old man
3. THE vertical uprights already purged of the marked part

There are no fixings, the waterproofing, the closure of the wall and the new thermal coat.

I think it is now interesting to analyze the situation mentioned above through one vertical section – Figure 3 – where you can observe the representation of a frame wall with a dormant or Wall base in larch laid directly in the foundation audiencewell below the countryside.

I immediately jump to our eyes theabsence of sheaths to protect the wood; Guaine who would not have definitively solved the problem but would have at least slowed down.

In fact, another great theme would open, which is that of the formation of interstitial condensation between the wooden wall and the adjacent sheath. The interstitial condensation, with the going of time, would bathe the wooden part favoring the formation of mushrooms and molds.

On closer inspection we can also notice the lack of separation between the screed of the sidewalk and the wooden wall; All this promotes the anaerobic phase compared to the aerobic one. Good rule wants that, once the state of fact is represented and in order to solve the problem, it is decided to start from a solution like the one represented in Figure 4that is to say Raise the wall tax By means of a curb in ca on which to place the already restored wooden wall.

It is good to reiterate that what is represented in Figure 4 It is nothing more than the starting point for a series of related reasoning:

• At the state of the art in which you are;
• To characteristics and to the quota of the surrounding land;
• TO how the house was structurally designed;
• At the Type of the wooden wall – frame, xlam, crossed and nail tables, etc.,
• To customer needincluding, not to be underestimated, the possibility or not to leave the property for the time necessary for the execution of the works.

It is important to remember that they are all invasive and very laborious interventionsas you act for small non -continuous fellow who must be followed by competent technicians with experience on the subject and made by highly qualified labor. These are interventions that can be compared to the architectural restoration of ancient buildingswhere it is necessary to carry out the backgrounds; On closer inspection, the intervention technique is very similar, with the difference that in addition to the reinforced concrete part you go to act in marching wooden structures.

Needless to say, before starting the structural restoration it is necessary have a planning plan and a structural calculation run by a qualified technician; This in order not to create problems for the existing structure and to restore, once the interventions are finished, a static situation identical to the already tested one.

Before, before postponing this topic to dedicated insights, indicate a starting point for the support of the wooden walls of a new construction. A simple realization as in Figure 5 would allow you to avoid in almost all cases the occurrence of everything described previously.

You can see the Cordolo in ca that comes out of the countryside, the sheath protection, i insulating panels first in style and then in rock wool, outwards, and the counterpart isolated inwards.
I conclude by saying that this should be the Acceptable minimum condition of good building.