Raising a tower crane is a regular part of every project in which the building rises above the height of the crane in its first configuration. Instead of erecting a tall crane from day one, work starts at a height suited to the first stage of the frame, and mast sections are added as the building progresses. When the crane reaches its free-standing limit, it is tied to the building and carries on climbing. This guide explains what determines the free-standing height, how climbing is carried out, what the structural engineer needs to receive, and how to fit the raisings into the construction schedule.
Free-standing height is the maximum height under the hook at which the crane stands on its base alone, without any connection to the building. Today there are cranes with a reinforced mast that stand without ties up to a height of nearly 100 metres (for example a Potain MDT 368 with a reinforced mast, up to 93.7 metres according to the data sheet). This is relevant mainly when there is not yet a building to tie to, but the crane must pass over neighbouring buildings or cranes within its working radius. The manufacturer calculates it so that the crane stands both in work and in the out-of-service condition, when the jib is free to slew with the wind. A crane’s free-standing height therefore depends on several factors together:
An example from the manufacturer’s documents: in the Potain MDT 268 product guide for the North American version, the maximum free-standing height on a K mast 2 m wide ranges from 52.5 m on a ZD 463 cross base to 74.9 m on a V63A chassis. That is, on the same crane and the same mast the difference is more than 20 m, because of the base alone. The document also notes that the values are based on an American wind standard for a particular zone, so they must not be copied to a site in Israel. The value for your site is taken from the manufacturer’s tables for the exact configuration and the local wind conditions.
The rule is simple: if the hook height needed to complete the building is higher than the free-standing height of the chosen configuration, the crane will be tied. In practice the decision is made already at the placement planning stage, because it affects the crane’s position relative to the building wall, the type of base and the length of the tie bars. Sometimes it is right to choose a heavier base to save one tie, and sometimes the opposite.
Two more things determine the number of ties. The first is the free height above the top tie: even on a tied crane, the manufacturer limits the mast section above the last tie frame. The second is the distance between ties along the mast, which is also defined in the manufacturer’s instructions. From this it follows on which floors anchor points will be needed.
A crane tie frame is a steel frame that closes around the mast at a height the manufacturer approves. From it, usually three or more bars run to anchor points in the building: a slab edge, columns or core walls. The bars usually include a means of length adjustment, so that the mast can be aligned vertically during installation. On the building side, anchor plates are fitted, cast in advance or bolted, according to the engineer’s design.
The geometry of the tie is not set on site. The distance between the mast and the building, the angle between the bars and the height of each tie directly affect the forces in each bar. So any change in the crane’s position after the tie has been designed requires recalculation. Details on tie frames for tower cranes are in the catalogue.
Once the crane is tied, the building becomes part of its stability system. Through the bars, horizontal forces from the lifting moment, from the wind and from stopping the slewing motion pass to the frame, and also torsion. The manufacturer supplies the forces for each configuration, usually separately for the working condition and the out-of-service condition. INRS notes in the same context that the loads the crane transmits to the foundations are provided by the manufacturer, and design and execution are carried out by professionals. The same logic applies to the tie points.
In the United States, the OSHA tower crane standard requires a registered engineer to verify, before every climb, that the host structure can carry the forces that pass through the bars, the anchors and the slabs. In Israel, the tower crane regulations state that the stability of a static crane must be secured by anchoring, connection or another suitable method, and that a structure on which a crane is placed must be strong enough. In practice, the project’s structural engineer needs to check:
What to pass to the engineer: model and configuration, the heights of the ties, the distance of the mast from the building, the force table from the manufacturer and a drawing of the frame and bars. The earlier this happens, the easier it is to include the anchor plates in the construction drawings.
A telescopic cage is a steel structure that wraps around the mast below the slewing part. INRS describes it as equipment that lifts the entire slewing part, that is, the jib, counter-jib and pivot, in order to insert additional mast sections without an external auxiliary crane. The cage comes from the same manufacturer as the crane, and is used according to the manufacturer’s instructions for its type of crane. It must also be confirmed that the mast itself is suitable for climbing: in the Potain product guide there is a separate marking for sections that are not intended for climbing and for climbing sections.
This is a general description. The number of steps, the balancing weight, the trolley position and the order of connections differ between models, and the governing document is the manufacturer’s climbing instructions for the model and mast on site.
There is also a method in which the crane stands inside the building, for example in a shaft, and climbs by leaning on the slabs with dedicated frames and a ram. INRS notes that in this method no mast sections are added, because the whole crane rises with the building. Here it is especially important that the structural engineer approves the slabs that carry the crane.
The tower crane regulations prohibit raising or lowering a crane when wind blows that could endanger its stability or the workers. The regulation does not state a number, so the practical value comes from the manufacturer. According to the HSE discussion document, manufacturers usually define a maximum wind speed for climbing, and a strong gust in the middle of the climbing cycle can load the cage heavily. The OSHA standard sets a similar principle: the wind speed the manufacturer recommends must not be exceeded, and if the manufacturer has not set one, a qualified person sets it.
A point it is important not to miss: the speed shown in the crane’s data sheet is usually the normal working limit. In the MDT 268 guide, for example, it says work is possible in gusts of up to 72 km/h. That is not the value for climbing. The climbing limit is taken from the climbing instructions themselves. Measure the wind at jib height, choose a window in which the forecast is stable for the whole duration of the operation, and define in advance who stops the work and how the crane is secured if the wind picks up in the middle. Do not leave the crane at the end of a working day with the upper part not connected to the mast with all the pins, according to the manufacturer’s instructions.
A good raising is planned weeks in advance. Build a simple table: the building height by floors and dates, against the crane’s hook height after each climb. This shows when the crane is approaching the roof of the building and when a tie is needed.
| Subject | Free-standing | Tied crane |
|---|---|---|
| Maximum height | Up to the free-standing height of the configuration | Higher, according to the number of ties and the height permitted above the top tie |
| What determines the height | Model, jib, mast type, base type and local wind | All of these, and also the tie distances and the strength of the structure |
| Loads on the building | None, all the load goes down to the foundation | Horizontal forces and torsion pass to the frame at the anchor points |
| Structural engineer’s involvement | Mainly in the crane foundation | In the foundation, the anchor points and the concrete strength on the day of installation |
| Position relative to the building | More flexible | Limited to the range in which tie bars can be designed |
| Effect on the facade | None | The anchor points leave work to close after dismantling |
| Schedule | Raisings up to the free-standing limit | Raisings and ties coordinated with the progress of the frame |
The Safety at Work (Tower Cranes) Regulations, 1966, are still in force, and several of them relate directly to this subject. Regulation 42 states that raising or lowering a tower crane is carried out only under the management and supervision of an expert in such operations or a crane operator specially trained for it. Regulation 43 prohibits raising in wind that could endanger the crane’s stability or the workers. Regulation 86 requires a thorough inspection by a certified inspector after erection and after any change to the crane’s structure before it is operated, and regulation 87 includes the raising and lowering mechanism in the scope of the inspection. If a raising or the addition of a tie on your site requires a re-inspection, clarify this in advance with the certified inspector and the safety officer. Draft amendments to the regulations were published for public comment in 2022 and 2025, and as of October 2026 we have not found a final text published in the official gazette. It is worth following the Ministry of Labor. A broader overview of the regulations is in the guide Tower cranes: types, lifting capacity, regulations and rental.
At RMA, the erection crews are part of the 60 staff, technicians and engineers, and are among the experienced, long-serving crews in the field. On projects with raisings, RMA’s engineering and service team starts from the final height of the building: it chooses a configuration and a base, marks the tie heights and passes the force data from the manufacturer to the customer’s structural engineer. Before every climb a working day is coordinated with the site manager, the wind forecast is checked, and the crew works to the Potain climbing instructions for the model on site. After the climb the crew updates the limits and safety systems and coordinates the required inspection. Details of the service are on the erection, raising and tying of tower cranes page.
If you are at the planning stage and want to check how many raisings and ties your building will need, you can start with a needs assessment and initial planning at no cost (an initial review of the site plan and a basic recommendation on model and position; a full placement plan is priced separately), or call the office on 08-9202882.
Raising is adding mast sections to increase the crane’s height, usually by climbing with a telescopic cage. Tying is connecting the mast to the building with a tie frame and bars, so that the crane can keep rising beyond its free-standing height. On tall projects the two are combined.
From the manufacturer’s tables for the exact configuration: model, jib length, mast type, base type and wind zone. The same model can get very different values on different bases, so a number is not copied from a general data sheet.
The project’s structural engineer, based on the forces the manufacturer supplies for the configuration. They check the local element, the anchor detail and the concrete strength on the day of installation.
Israeli regulations prohibit raising in wind that could endanger, without stating a number. The practical value is the climbing limit in the manufacturer’s instructions for the model, which is different from the normal working limit in the data sheet.
Regulation 86 requires a thorough inspection after any change to the crane’s structure before it is operated, and the raising and lowering mechanism is included in the scope of the inspection. Clarify in advance with the certified inspector and the safety officer what is required for a raising or a tie on your site.
It depends on the model, the number of sections, whether a tie is needed and the wind conditions. During the climb the crane does not lift materials, so the day is coordinated in advance with concrete pours and deliveries.
The information in this article is general and does not replace engineering, safety or legal advice for a specific site.
This site uses essential cookies and Google Analytics cookies for aggregate usage measurement. You can decline measurement cookies and the site will keep working normally. Privacy Policy
Hebrew