Removing a load-bearing wall: what shoring is and how it is done

More and more of our clients decide to change the layout of their home in a full renovation to suit their tastes or needs. Homes are becoming more open, with fewer rooms and the kitchen joined to the living room. Achieving this means changing the original layout, which usually involves knocking down or “moving” a wall. Before making that decision, there are several things to consider.

In this article we take a simple look at the most important points to check before removing a load-bearing wall.

Is it a structural wall?

The first step is to make sure the partition is not actually part of the building’s structure. This is not always easy to tell: over time, a partition wall may have settled and, to compensate for the deflection of other structural elements, some non-structural elements end up carrying load.

Be careful! Over the years, some partitions may have become load-bearing walls.

To get an idea of which walls can be removed and which cannot, you can apply a quick rule of thumb, although a professional should always assess it. If the wall is more than 40 cm thick, it is probably a load-bearing wall and therefore part of the building’s structure. If it is less than 10 cm thick, it is most likely a partition that can be “moved” without affecting the structure. In many cases these rules do not hold, so the final assessment must be made by an expert.

Whenever this kind of work is carried out, you need an architect or building surveyor to check, using the building plans and a site visit, what the structural system is and what role the walls you want to change play.

If it does turn out to be a structural wall, the renovation can still go ahead using shoring (an “apeo”), but the process will take longer and cost more.

What if it is a partition with services inside?

Care is needed when removing partitions, especially when the floors are made of old timber joists. This kind of structure deforms a lot over time: the joists gradually sag (deflect). When this happens, the ceiling can end up resting on the partitions and, when one is demolished, the neighbour’s partition upstairs may crack, or tiling or another finish may break.

Once we have ruled out that the partition we want to demolish is carrying load, we need to check the services that run through it.

When we confirm that the wall is not part of the structure, before opening it up or knocking it down we must make sure no service ducts run inside it. It is common to find electrical cables, plumbing pipes or, in the worst case, the home’s gas pipe hidden inside partitions.

The appointed professional must check, using up-to-date building plans, that there are no services inside the partition to be demolished. This must be done before work starts: knocking down a partition with a pipe or cable inside can cause expensive damage and can also be very dangerous.

If services are found inside the partition, the renovation can still go ahead: the affected supplies must be cut off and the pipes or cables rerouted through other parts of the home. Because of the risks of faulty installations (gas or water leaks, electric shocks), this work must be done by qualified personnel.

The wall is structural: what is shoring?

Shoring is the diversion of loads, usually by means of a beam, to change the original load path of the building. Shoring is normally carried out in two stages: temporary shoring, with props, needles and pins, a temporary construction that supports the structure while it is being altered; and permanent shoring, where the structure is left “open” and in suitable safety conditions.

There are many types of shoring. The professional will choose the system depending on the loads on the wall, its thickness, the layout of the other structural elements, the size of the opening and other factors.

Shoring with notching on both sides of the wall

This type of shoring is used for short spans and low loads, as it is very risky if carried out without temporary shoring.

Shoring with packing of the wall over a lower beam

A beam is placed so that it is usually embedded in the full thickness of the wall, which requires full temporary shoring. It is suitable for large spans.

Shoring by confining the wall

With this type of load-bearing wall shoring (the first diagram in the figure, a1) the wall does not need temporary shoring, and it is the safest option if the builders are not very experienced in this kind of work. It is usually suitable for low loads. A beam is placed on each side of the wall and the two are joined with connectors, usually threaded bars set in epoxy resin.

Option c is the safest and the right one for large spans and heavy loads. It must be carried out by professionals who specialise in this kind of work.

Steps to remove a load-bearing wall

1. Preliminary studies

Once the points above have been studied in broad terms, a technical design must be drawn up to define the structural sizing and the construction procedure.

2. Design

The design includes a study of the existing loads on the building, paying special attention to the wall and foundations being worked on and, above all, to any unusual features or unexpected alterations on the floors above and below.

A study of the modified loads is then carried out to check that diverting the loads in the wall does not create situations that compromise the safety of the lower floors and the foundations.

Finally, the new structure is sized in line with the regulations: the Spanish Building Code (CTE) on actions and, usually, on steel structures. Both ultimate limit state resistance and deformation limits are checked, the latter usually being the most demanding:

The calculation limits the deflection of the new beams to 1/500 or 1/1000 of the span. In other words, a 2-metre beam cannot deflect by more than 2 mm.

And that is after applying safety factors to the loads and reduction factors to the strength of the materials. You can read what a basic and execution project should include here.

Once the design is finished, the building permit can be requested. Remember that, under Article 128 of the Barcelona Metropolitan Ordinances, neighbours must be notified that the project exists and that they can consult it.

3. Construction

Although it is a simple operation, it is high-risk, so every step must be planned and carried out carefully. The builders should have experience with this kind of work, and whoever welds the steel sections must be able to make continuous welds of the thickness specified in the design, clean and free of pores.

Example: double steel sections on concrete pads

Diagrams from the preliminary studies

Plan and section of the area to be demolished and the elements to be built:

Design details

In this project we chose shoring by confining the wall. We carried it out in Terrassa, as part of the full renovation of a penthouse. This is the elevation detail of the composite shoring beam:

And this is the cross-section detail of the same beam:

Construction procedure, step by step

Step 1. The work area is defined. In our case there was an opening on the left that is closed up (a wall is built, marked in red in the drawing). To avoid transferring loads to the floor below, this new wall is also shored from underneath so that the load path stays the same. The wall finish (usually plaster) is removed and test openings are made to check that what was built matches the design, if this has not been done before. The false ceiling and flooring next to the wall are removed to expose the masonry and see where the floor joists rest on the wall. Finally, the shoring is marked out.

Step 2. The floor above is propped with raking props that carry the loads down to the base of the wall, so that the building’s load path is not interrupted during the works. Straight after the props are placed, small openings are made to build the concrete pads on which the beams will rest.

Step 3. A steel section is placed on the concrete pads, acting as a capital that transfers the load of the two beams, one on each side of the wall, to the pad. The parts of the steel sections resting on the pads are packed with non-shrink mortar.

Step 4. With the temporary structure (props) and the steel sections in place and fixed, the wall is demolished.

Step 5. The opening is now finished; all that remains is to reapply the finish and reinstate the flooring and false ceiling removed in step 1. In this type of shoring, demolishing the wall is the last step (in many others it is not), which makes it one of the safest methods.

This is the final result. The concrete pads are not visible because they have been plastered over.

Conclusions

Removing a load-bearing wall must be done by qualified professionals. Each case must be studied carefully to comply with current regulations and to ensure safety during and after the works.

If you want to open up or remove a load-bearing wall, at KAITEK we draw up the load-bearing wall shoring design and support you throughout the process so that it is simple and safe. Tell us about your project.