The Ladder-access tower scaffolding module checks tube and fitting ladder-access tower scaffolding for compliance with TG20:21. A ladder-access tower is a personnel access structure attached to an independent scaffold, loaded to a maximum of 1.0 kN/m², which must not be used for the storage of materials.
All permitted TG20:21 compliant ladder-access tower configurations can be checked, including:
The software checks whether the ladder-access tower is TG20:21 compliant and, if so, calculates the maximum leg load for the foundation design and the maximum tie duty. The calculation will also determine:
The tower design criteria can be specified, or set to Automatic so that the TG20 compliance check determines them. If the tower fails the safe height check, the software suggests options to modify the tower design criteria to pass, which can be applied from the Options tab.
The following sections provide details of the user inputs required, and also explain the outputs provided by the software.
The display panel options are similar to that of the Tied independent scaffolding module, with the following options available:
A map is provided to search for the site address and specify the site location. You can input the address in the same way as for the TG20:21 wind factor module. The site address (in the right-hand panel) is populated automatically from Google Maps services. This address can be manually overwritten if required.
The site wind factor is automatically calculated from the site location, in accordance with Appendix A.2 of the TG20:21 Design Guide, as also described for the TG20:21 wind factor module.
A 3D preview of the ladder-access tower is displayed, with a cut-line display of the tied independent scaffold to which it is attached. The 3D preview updates as the input options are selected. Holding down the left mouse button will allow you to rotate the view, the mouse scroll wheel can be used to zoom in or out and holding the right mouse button will allow you to pan the view.
2D illustrations of the ladder-access tower are provided in first-angle projection, displaying the front elevation, side elevation and plan view.
A summary report is provided when the calculations are performed, including the 2D elevations, the ladder-access tower configuration and dimensions, the calculated leg load and tie duty, and the results of the TG20:21 check.
The following options are available for selecting the site location:
| Input | Description |
|---|---|
| Site details | The site address can be selected by searching for an address from the Search bar above the map, or by moving the site marker. This address can be manually overwritten if required, which does not alter the location of the site on the map. |
| Consider sheltering from nearby buildings | Select this option to reduce the wind exposure by considering the sheltering effects of nearby buildings. The sheltering effect is only applicable to wind sectors that are calculated as being within town terrain. |
| Design life | Select if the structure is a temporary structure (≤ 2 years) or if it is a long- standing/permanent structure. |
| Standing during | Select the spring and summer option to reduce the wind exposure for scaffolds or temporary structures standing only between April and September. This option is applicable only if the design life is set as ≤ 2 years. |
You can enter the scaffolding dimensions by selecting the Scaffolding tab, this will automatically switch the display from the map to the 3D model. The 3D model updates whenever the inputs are modified.
The following inputs can be specified for the ladder-access tower:
| Input | Description |
|---|---|
| Boarded lifts |
Select whether the ladder-access tower will be boarded at every lift, or at alternate lifts with the top lift boarded. A ladder-access tower is a personnel access structure, loaded to a maximum of 1.0 kN/m², and must not be used for the storage of materials. Where the lift height is up to 1.5 m, a ladder-access tower of more than one lift must be boarded at alternate lifts to be TG20 compliant. |
| Tower bay length |
The maximum bay length of the ladder-access tower, which may be reduced below the bay length of the independent scaffold to increase the maximum safe height of the tower. If Automatic is selected, the bay length is reduced as required by the TG20 compliance check and reported. |
| Tower tied at |
Specifies whether the ladder-access tower is tied with lines of ties at alternate lifts or at every lift. The tower must be tied at least as frequently as the independent scaffold to which it is attached. Where the lift height of the independent scaffold exceeds 2.0 m, the tower is tied at every lift. If Automatic is selected, the tie interval is determined by the TG20 compliance check. |
| Tower top lift tied |
Specifies whether the ladder-access tower is tied at the top lift at both end standards, with additional ties where the tie pattern does not already provide them. A tied top lift is required for a clad scaffold, a single-lift scaffold, or where required to achieve the specified scaffold height. If No is selected, the top lift is tied only as the tie pattern provides. Where the lift height of the independent scaffold is up to 2.0 m, a tower tied at every lift is tied at alternate end standards in a diamond pattern (tie pattern D), so its top lift is tied at one end standard. Where the lift height of the independent scaffold exceeds 2.0 m, the tower is tied at both end standards at every lift (tie pattern A), so its top lift is always tied. If Automatic is selected, the requirement for a tied top lift is determined by the TG20 compliance check. |
| Double standards |
Specifies whether the standards of the ladder-access tower are doubled to increase their load capacity, as described in TG20:21 Operational Guide section 6.21. The selection also applies to the independent scaffold, whose standards may also need to be doubled. If Automatic is selected, the standards are doubled if required by the TG20 compliance check. |
| Double standards height |
The height of the secondary standards of the ladder-access tower in metres, which must be at least the height required by the TG20 compliance check. The height also limits the double standards of the independent scaffold. This input is only required when the double standards option is set to Yes. If the double standards option is set to Automatic, the required height is calculated by the TG20 compliance check. |
| Foot lift |
Specifies whether the ladder-access tower has a foot lift, as described in TG20:21 Operational Guide section 6.10. A foot lift may be required to stabilise double standards, depending on the wind factor. If Automatic is selected, the foot lift is determined by the TG20 compliance check. |
The following inputs can be specified for the independent scaffold to which the ladder-access tower is attached:
| Input | Description |
|---|---|
| Load class |
Select the load class of the scaffold to which the ladder-access tower is attached, in accordance with EN 12811-1 and TG20:21 Operational Guide section 6.3. |
| Maximum bay length |
The maximum bay length for the scaffold, limited by the load class and platform width as in Table 2.1 of the TG20:21 Design Guide. |
| Scaffold base level |
The vertical distance between the ground level and the base of the scaffold, in metres, for use when the scaffold is supported on a building or other structure. This value should be zero if the scaffold is founded on the ground, as the elevation level of the ground is calculated automatically by the software. |
| Lift height |
The maximum scaffold lift height, in accordance with section 6.5 of the TG20:21 Operational Guide. Lift heights of up to 1.5 m may be used for raising brickwork and similar works, as introduced in the September 2026 edition of TG20. TG20 considers that such scaffolding will be boarded at alternate lifts, so a maximum of 50% of the lifts of the independent scaffold and of the ladder-access tower may be boarded. If the lift height is changed to 1.5 m or less, a fully boarded scaffold and a tower boarded at every lift are changed to alternate lifts boarded. |
| Scaffold lift boarding |
Specifies which of the scaffold lifts are boarded: the top lift only, the top two lifts, the top lift and the alternate lifts below it, or every lift. The Top lifts boarded (other) option allows the numbers of boarded and unboarded lifts to be entered, with the lifts boarded from the top lift downward. Otherwise, the total number of lifts is entered. |
| Number of lifts |
The total number of scaffold lifts, whether boarded or unboarded. |
| Number of boarded lifts |
The maximum number of boarded lifts. Any lifts that are partially boarded, such as ladder landings, should be conservatively considered to be boarded. |
| Number of unboarded lifts |
The maximum number of lifts that are not boarded. |
| Platform width in boards |
The maximum width of the scaffold platform in boards, in accordance with section 6.4 of the TG20:21 Operational Guide. |
| Inside boards |
The maximum number of inside boards, in accordance with section 6.4 of the TG20:21 Operational Guide. |
| Cladding |
Select from:
All references are to the TG20:21 Operational Guide. The ladder-access tower is unclad, or clad with debris-netting or sheeting, as for the independent scaffold. |
The following additional inputs can be provided for the materials and the façade to which the scaffold is tied:
| Input | Description |
|---|---|
| Tube material |
The tube material from which the scaffold will be constructed, in accordance with TG20:21 Operational Guide section 4.1:
The tube material can be identified on delivery with a stamped marking or attached tag stating the steel designation, for example ‘EN 10219 – S 355 JOH’. |
| Facade permeability |
Specifies whether the façade to which the scaffold is tied is:
This is defined in section 6.22 of the TG20:21 Operational Guide. Free-standing scaffolding not tied to a façade, such as for timber frame construction or demolition, is not in the scope of TG20:21 or this software. |
| Tie capacity is known |
Specifies whether the capacity of the building fabric, anchor and tie assembly is known, as described in section 7.10 of the TG20:21 Operational Guide. If so, the calculated tie duty is compared with the tie capacity and a pass or fail result is reported. If not, the calculated tie duty is simply stated in the calculation report. |
| Tie capacity |
The maximum permitted tie duty for the building fabric, anchor and tie assembly, as determined from preliminary anchor testing described in section 7.18 of the TG20:21 Operational Guide and the tie assembly capacities stated in table 7.2. |
You can specify a pavement lift for the independent scaffold, if required, on the Add-ons tab.
| Input | Description |
|---|---|
| Pavement lift |
Specifies whether the independent scaffold will include a TG20:21 compliant pavement lift to act as a pedestrian thoroughfare in accordance with TG20:21 Operational Guide section 10.2. With a pavement lift, the first lift of the ladder-access tower is at 2.7 m. |
| Stabilisation |
Determines how the pavement lift will be stabilised, as described in TG20:21 Operational Guide section 10.3. The following options may be used:
If the scaffold has only a pavement lift it must be stabilised using ties. The other options require at least two lifts. |
The Options tab is displayed after performing the TG20 compliance check if the ladder-access tower fails the safe height check and the calculation has found options to modify the tower design criteria to pass.
Select one of the displayed options and press the Fix button to apply it to the tower design criteria and repeat the TG20 compliance check. The options are also listed in the TG20:21 check section of the compliance report.
Each option states the changes to the specified tower design criteria that increase the maximum safe height of the tower, which may include:
