When we talk about reinforcing, we mean that technique of consolidating masonry structures carried out with the aim of limiting subsidence and giving greater support to the structure.
The word itself defines the basic concept: by means of a tying system that constricts the structure within the shape made, the process of deformation that can evolve into structural failure is prevented.
In construction, the reinforcing technique is used both on individual structural elements and on entire buildings for renovation purposes, or in cases where a passageway such as doors and windows is opened and a technique for consolidating the surrounding structure is needed. In the latter case, the reinforcement work will replace the previous portion of the wall that performed the function of a load-bearing element.
INDICE ARTICOLO
Load-bearing wall reinforcement, what is it?
Reinforcement is inserted to block the forces acting on columns and piers, to strengthen them and give more support against stress and possible failure.
When performing work on the interior of masonry or stone houses, great care must be taken to keep structural features unchanged, especially when inserting new openings.
Failure to carry out certain interventions could result in cracks and subsequent collapse of the wall or in the worst case, a portion of the structure.
In fact, the intervention of removing portions of wall area makes the wall less resistant and rigid; for this very reason, it is necessary through a steel or reinforced concrete reinforcement technique, to restore the original state of the strength of the wall.
The materials chosen to proceed with reinforcement, whether steel or reinforced concrete, must be selected according to different needs and according to the work to be done on different types of structures and walls, as they may possess different characteristics of both strength and ductility despite the fact that the end result on different walls is very similar.
The installation procedure also varies depending on the two methods chosen, so it is essential to assess the situation by getting help from experts in the field to proceed with the most suitable method.
Reinforcement the load-bearing stone wall is done using steel stringers or girders, a kind of metal brackets that are welded together and attached to the masonry with dowels.
All removal of the masonry portion and the resulting reinforcement on load-bearing wall must be carried out by experienced technicians, following the proper inspections of the structure.
Stages of opening on a load-bearing wall
In order to open a space, a passageway, whether a door or window within a wall, it is necessary to intervene by means of a reinforcement technique that will return the structure to its initial situation of strength and resistance, capable of supporting stresses and loads in the same way.
To begin with, it is necessary to identify the type of wall on which the work is to be done, trying to figure out whether it is a load-bearing wall or a simple partition wall.
Opening on a load-bearing wall is a job that must be done carefully and requires certain steps consisting of well-defined steps:
· identification of the exact point where it is necessary to remove the portion of the wall that will determine the opening;
· shoring of the slab placed in the direction, to exclude that portion from the structural stresses that will be created;
· fabrication of the upright braces, performing the work from the bottom upward;
· insertion of the platband, necessary to support the overlying masonry. This is an element commonly composed of metal sections called girders, fastened together with bolts and anchored to the sides using cement mortar;
· making the jambs, abutments and base of support, again using girders connected to the structure using dowels;
· only after making sure that the cement has set properly and proceeding from top to bottom, it is possible to proceed with the demolition of the portion of the wall that will create the passage, so as to obtain the opening of the passage.
Reinforcing tuff structures
There are cases where door and window openings are not made near load-bearing walls, although today, it is very rare to find certain circumstances, precisely because windows are installed on the perimeter walls that are load bearing by definition.
In these cases, the procedure for the execution of reinforcement on tuff or generally dry-stone masonry is almost similar, using a metal frame, or made of reinforced concrete.
The major difference lies in the space between two outer elements, which is then filled with mortar and lime to join the pieces of rubble stone.
This kind of structure has a lower strength than solid masonry and a greater possibility of degradation, therefore, reinforcement is often carried out even in cases of existing door or window openings, with the aim of strengthening them.
Lintel or reinforcement?
When interventions need to be carried out to open a passageway in which to insert a door or window, it is necessary to identify the best method to ensure a structure with optimal resistance to various stresses.
There are two different methods to proceed, namely the insertion of a lintel or using a reinforcement technique.
We have seen how the implementation of reinforcement is necessary in cases where one is close to load-bearing walls, so there is no other way to proceed; but in what cases is it possible to intervene, instead, by inserting a lintel?
The task of the lintel is pretty much the same, then, to support the load of the structures above, but to transmit it vertically to the lateral structures on which it rests.
A classic example of a lintel, which we all have well in mind, is the Trilithic system of the stones at Stonehenge, consisting of a structure with two vertical elements called piers, which support a third horizontal element, positioned above, called the lintel.
Over the years, lintels have been constructed of different materials, up to the current ones composed of prefabricated trussed hallow-core concrete, used in masonry construction and non-load-bearing partitions.
In order to proceed with the most suitable method, it is necessary to understand whether the wall in question is a load-bearing type or not.
Expert help would be the ideal solution; it is generally very easy to deduce what the nature of the wall is, through certain characteristics.
One of the most significant is the thickness of the wall, which, if less than or equal to 10 cm, often indicates a non-load-bearing wall.
Be careful not to replace intuition with an actual identification procedure performed by experienced technicians, which is essential when it comes to structural work. In the case of a non-load-bearing wall, it is possible to proceed with the insertion of a lintel, while if it is a load-bearing wall, it will be necessary to make further investigations to see if reinforcement should be done.
The major difference between the two interventions lies in the load-bearing capacity, as a lintel can only transfer vertical loads, whereas in the case of a load-bearing wall, strength and stiffness with respect to horizontal stresses must also be restored.
Reinforcing Load-bearing Wall Regulation
In order to open a gap within a load-bearing wall, it is necessary to follow requirements dictated by the regulations:
· a residual lateral masonry deck of at least 50 cm must be left from the perpendicular bearing wall, except in cases where the wall on which the reinforcement work is being carried out, goes beyond that in the orthogonal direction;
· the state of stiffness achieved as a result of the reinforcement works should not be very different from that in the initial state, therefore, it is essential to carry out a check both before and after the works, to certify that the stiffness of the wall is almost the same.
With regard to the regulations and the necessary permits that must be submitted in order to proceed with reinforcement intervention on a load-bearing structure, specific paperwork must be provided.
In the case of a reinforcement intervention that is feasible as a Local Intervention, it is necessary to submit a seismic file that has as a building title of Segnalazione Certificata di Inizio Attività , S.C.I.A., which falls under extraordinary maintenance interventions.
This is information to be communicated to the municipality, through which the start of work is made known. The current S.C.I.A. has replaced the previous D.I.A., which represented the Declaration of Commencement of Activities, bringing improvements in timing, in fact, the S.C.I.A. can even be submitted on the same day of the start of work, precisely because it is a practice that does not require approval.
On the other hand, as for the time required to carry out the S.C.I.A., it depends on both the time required to draw up the file and the time required by the professional engineer to create the plans.
Two other documents that are indispensable to be able to carry out the work are the structural file to be filed with the Civil Engineers and making a cadastral update carried out by the structural engineer.
What, on the other hand, is not allowed to be performed as part of local interventions are the operations listed here:
· the use of uprights in the masonry intersection or in the thickness of cross walls;
· the insertion of reinforcements placed straddling the intersections of walls;
· the opening in an exterior perimeter type wall with a distance of less than 1 m from the corner, also considering the thickness of the cross wall;
· it is not possible to totally eliminate a load-bearing or bracing wall, except in exceptional cases for which major checks are carried out.
Cost to Reinforce Load-bearing Walls
The costs to be considered for the reinforcement of a load-bearing wall are different, such as that for the design, for the direction and organization of the work, and for the work done by the freelancers who will contribute to the intervention, a total that can range between €800 and €1,300.
On the other hand, considering the cost of carrying out the building intervention and installation, we generally start from a sum of 1,500 €, up to 3,000 €.
Prices may vary according to the specifics of the work to be performed, depending on the materials, the thickness of the wall, the structural characteristics, according to the different figures you rely on and also according to the different areas of the territory.