ANTI-SAG SUPPORT FOR STANDARD ROOFS
Managing Deflection during cladding installation – Quick reference chart
The chart below provides guidance on the requirement for anti-sag supports during cladding installation. It must be read in conjunction with the terms of use listed underneath.
| Number of rows of anti-sag ties per bay based on span and roof pitch | ||||
|---|---|---|---|---|
| Roof Slope (°) | Purlin section | Bay Centres (m) | ||
| Up to 6.1 | Up to 7.5 | Up to 9 | ||
| 4 – 10 | Up to 265 | 0 | 1 | 2 |
| 10 – 20 | Up to 265 | 0 | 1 | 2 |
Terms of use
The information contained above may be applied subject to the following restrictions and conditions.
• The guidelines apply where screw fixed steel sheeting is used. The cladding used must provide full restraint to the top flange of the purlin.
• Tube Ties or Threaded Rod Ties may be used with the sections listed above.
• For sections greater than 265 the more substantial support provided by Angle Struts is recommended. The frequency of use is dependent on bay centres and is generally similar to that listed in the table above however please contact Duggan Profiles to discuss specific cases.
• There are additional requirements for roofs over 20° or slope lengths greater than 20m to avoid overloading the anti sag components. Refer to Additional requirements for long slopes, steep slopes or heavy cladding during installation.
• The information outlined above is suitable for managing deflection during cladding installation. They may not be applied where wind uplift may be an issue and equally should not be used where heavy roof loads or non restraining cladding leave the top flange under restrained. Refer to Anti sag support for wind uplift and Anti sag support for non restraining roof cladding for appropriate recommendations.
• Apex Ties are required in all situations where anti sag ties are used.If this is not possible some other form of anchor support such as Tie Ropes must be used. Refer to Additional requirements for long slopes, steep slopes or heavy cladding during installation for details on use of Tie Rope in roofs.
• There are additional requirements for roofs with a single slope. Refer to Additional requirements for Mono Pitch Roofs.
• These guidelines are not applicable to flat roofs (pitch < 4°). Refer to Anti sag requirements for Flat Roofs.
ADDITIONAL REQUIREMENTS FOR MONO PITCH ROOFS
In the general “A” roof situation purlins are tied to standard Apex Ties spanning the apex using either Threaded Rod Ties or Tubular Ties. Where this is not possible (eg. where a Mono Pitch Roof is used) an alternative means of support must be provided. An adapted version of the standard apex tie may be feasible as shown here.
ANTI SAG FOR CURVED ROOFS
Tube Ties or Threaded Rod Ties may be used in conjunction with an Apex Tie. Due to the constantly changing gradient of the slope Tube Ties will not fit in succession as is normally the case. Instead the offset arrangement shown in the diagram below can be used. Threaded Rod Ties are fitted in a similar manner.
ADDITIONAL REQUIREMENTS FOR LONG SLOPES, STEEP SLOPES OR HEAVY CLADDING DURING INSTALLATION.
On longer slopes it may be more difficult to maintain accurate sheeting lines using the normal anti sag arrangement. Where additional support is required Tie Ropes can be added at intervals along the length of the slope to transfer a portion of the load to the main structure. The table below lists guidance for the more common situation. For more comprehensive details please contact Duggan Profiles for advice.
Number of Tie Ropes based on length of slope
| Roof slope (°) | Purlin section | Length of slope | |
|---|---|---|---|
| < 20m | ≥ 20m | ||
| 4 – 10 | Up to 265 | Tie Ropes not generally required | Use a set of Tie Ropes for the first 20m section of roof and an additional set for each 10m section thereafter. |
Terms of Use:
• The information contained above may be applied subject to the following restrictions and conditions. It is also advisable to seek guidance from Duggan Profiles as the information provided is of a general nature and inadequate to cover all possible scenarios.
• The guidelines apply where screw fixed steel sheeting is used. The cladding used must provide full restraint to the top flange of the purlin. For roofs over 20° or sections greater than 265 Angle Struts should be used instead of Tube Struts. It is also advisable to contact Duggan Profiles as the frequency of Tie Ropes may need to be increased.
• The information outlined above is suitable for managing deflection during cladding installation. They may not be applied where wind uplift may be an issue and equally should not be used where non restraining cladding leaves the top flange under restrained. Refer to Resisting the torsional effects of wind uplift and Resisting the torsional effects on under restrained top flange for appropriate recommendations.
• Apex Ties are required in all situations where anti sag ties are used. If this is not possible some other form of anchor support such as Tie Ropes must be used.
• These guidelines are not applicable to flat roofs (pitch < 4°). Refer to Anti sag requirements for Flat Roof.