Welcome to our Frequently Asked Questions:

Can I buy or hire products directly from DESSA?

We are a business to business wholesale company and sell through a network of approved hire and sales outlets. You can find your nearest outlet here.

Where can I find my local distributor?

You can find your nearest distributor here.

How do I become a distributor?

If you are interested in becoming a distributor for our products please use our online form or contact info@altrad-dessa.com.

Can I get replacement spare parts for DESSA products?

Spare parts are available for a wide range of our products. Please contact +44 (0) 1480 475297 or admin@altrad-dessa.com and one of our team will assist you.

Where can I find technical information on a product?

To obtain technical information on our products please use our online form or contact info@altrad-dessa.com.

Where can I find DESSA products in the EU?

We have distributors all over Europe. You can find your nearest stockist here.

Where can I get a DESSA product catalogue?

Each product range features a catalogue under the Resources section of the product page on our website.

Do DESSA offer a steel cladding system?

Yes. We offer a steel purlin based system secured with special purlin couplers.

What is DeepFlow™ tracking?

DeepFlow™ tracking is a heavy duty aluminium profile with integral gutter system which allows for the installation of sheeting to temporary roofs or side wall cladding elements.
Features and benefits include:
• Integrated joining method – less parts on site, eliminating manual assembly.
• Efficient rainwater channeling using integrated sealed spigot.
• Fully compatible with existing DESSA roofing elements.
• Strong aluminium profile enabling 2.0-2.4 bracing intervals.
• Removable spigot to enable staggered bays if required.
• Increased weatherproofing.

Full details can be found on the DeepFlow™ tracking section of our website.

What is sysTRAX™?

sysTRAX™ is the first fully modular, high capacity rolling track system for temporary roof and scaffolds which enables elimination of horizontal loads for crane built and roll out roofs. Full details can be found on our sysTRAX™ section of our website.

What are the longest beams DESSA offers?

We can manufacture beams of any length to suit any application. From stock, on the basis of satisfying ease of handling and weight, we manufacture to the following lengths for our beam series:

• 45cm alloy – up to 8.1m.
• Asterix 75cm / D78 – up to 6m.
• Asterix HD 133cm – up to 4m.

For non-stock lengths, please use our online form or contact info@altrad-dessa.com.

Why has my roof failed on EstAssist?

The EstAssist checks are not comprehensive and make a number of worst case assumptions. EstAssist is not a design package and all temporary roofs should be designed and validated by a competent design Engineer. We operate a contract design service to all our clients, contact us for further information at engineering@altrad-dessa.com

Do you have a guide for EstAssist?

EstAssist has a User Guide built into the software which can be accessed using the Help menu.

How can I get EstAssist?

To obtain EstAssist please request using our online form or contact info@altrad-dessa.com.

What is a tie bar, why might I need one?

A tie bar is a systemised set of tubular elements that provide a connection between the bottom chords of roof trusses on a duo-pitch roof span. This system prevents the roof from spreading under large downward loads. When laced effectively, it also provides additional resistance against uplift forces. It may be considered for projects requiring a large span, projects subject to heavy snow loads or downward wind loads, or projects with limited tying possibilities.

What is the biggest span achievable?

This is very much subject to a variety of factors, including but not limited to:
• Location
• Environmental loads.
• Duration of project.
• Bay size.
• Support structure.

In moderate climate and exposure the following maximum spans can be expected:
• 450 series – in excess of 20m.
• 750/780 series – in excess of 30m.
• Asterix HD – in excess of 50m.

Why does my monopitch roof need to be at a 15 degree pitch?

A 15 degree inclination allows water to run off the roof without excessive water depot build up, avoiding water ponding and ingress in to the sheet tracking. Use of DeepFlow™ tracking allows for roof pitches to be made shallower and has been proven on spans pitched at 10 degrees.

What is the weight of UNI Roof/AHD as a system?

Based on 2.5m bays UNI Roof is 8-10kg/m2 and Asterix HD is 13-15kg/m2.

Can my tie bar be laced in scaffold tube to enable compressive and tensile capacity?

Yes. A quicker alternative is to use DESSA bracing elements.

How high can my UNI shelter go before I need to consider a vertical beam?

It is recommended that no taller than a 2.5m standard should be used on a UNI shelter.

I only have a four hole spigot, will my D78 beam still achieve its full capacity?

Providing a four hole connection will result in the joint governing the strength of the overall beam. Therefore the capacity of the D78 beam will be reduced. Details of the reductions are shown in our technical information sheet TIS17001.

Can I connect puncheons to the posts of a D78 beam?

No. According to EN 12811-1, cl., alloy tubes should not be connected to if their thickness is less than 4mm. The posts of the D78 beam are less than this. Full guidance on where to connect puncheons across our full beam range is shown in Beam User Guide USG001.

Can DESSA quick release pins be used on vertical bolted connections of system scaffold standards?

For standards of 48.3mm diameter, quick release pins AF0001 can be used. These pins are designed to suit a 12mm hole with 48.3mm outer diameter tube.

Are the roof sheets re-useable?

Yes. Care should be taken to pack and store the sheets following use. They should be inspected for damage, dried and pan folded with no sharp creases. We recommend they are stored in bags and inside.

How long do the roof sheets last?

Around 8-10 years, with a single job use of 2-3 years. We also offer a lightweight single use sheet and a heavy duty sheet for more onerous projects.

What is the minimum slope for a mono pitch roof?

To TG9:20, the minimum advisable pitch for a monopitch roof is 10 degrees. We advise 15 degrees to avoid such issues as water ponding and deflections in tracking joints. Our DeepFlow™ tracking allows for roof pitches to be made shallower and has been proven on span pitched at 10 degrees.

Why are roller braces needed?

Roller braces are not structural; however they are required for two main reasons:

• To assist sheeting installation by providing a rolling point at directional changes.
• To ensure the sheets are evenly tensioned.

Why are alloy track spigots needed when using DeepFlow™?

Alloy tracking spigots are used as an installation aid ensuring adjacent lengths of track are secured to each other and to prevent separation and sliding.

What is the safest method to build a roof?

The rollout method is the safest of the roof erection method as it allows the operators to erect the roof from a safe working platform (being a stepped gable end scaffold).

Is there a CISRS course for roofs?

There is no certified course for temporary roofing. We offer specific product training and first-time site hand-holding to assist with product familiarisation and site applications.

Do I need to be a qualified scaffolder to erect a temporary roof

Yes. Temporary roofs are complex structures that can impart large forces into the scaffold and supporting structures. Additional experience and knowledge is required to ensure safety and works should be only be undertaken or supervised by advanced level scaffolders.

Do I need to have drawings and calculations for every roof?

Yes, scaffolds with temporary roofs are Encapsulation Constructions as defined by BS EN16508 and beyond the scope of ‘Basic Scaffolds’ as defined in TG20. Temporary roofs are complex structures that can impart large forces into the scaffold and supporting structures, the overall stability and integrity of the structure needs to be assessed and detailed by a qualified and competent Engineer.

What additional design measures are needed if I add a temporary roof to my scaffold?

Temporary roofs are complex structures that can impart large forces into the scaffold and supporting structures, therefore the overall stability and integrity of the structure needs to be assessed and detailed by a qualified and competent Engineer. As a general rule, a scaffold supporting a temporary roof will require more anchors, bracing and ballast than a physically tied independent scaffold.

Do DESSA supply risk assessments and method statements for temporary roofs?

We supply designers risk assessments as part of our contract design service and can offer advice and examples of risk assessments and method statements to contractors involved in erection of temporary roofs.

Do your roofs fit any scaffold? How do I connect the roof to a scaffold?

Our temporary roofs can be fitted to any supporting scaffold structure. We provide support components to integrate seamlessly with system scaffolding and a range of lattice girders to provide a continuous roof support in installations where the supporting scaffold and roofing members do not align.

How do I open a roof for crane access?

This can be achieved through rolling roofs or pre-planned “access bay” positions. Having a rolling roof over an opening, and moving it to one site is a quick and efficient way to open the roof. Installing horizontal braces to the underside of the top chord on the unbraced bays allows a fixed roof to be easily accessed by removal of sheets and horizontal braces.

Can I lift more than a pair of braced bays at once?

Yes. Multiple bays can be erected on the ground and lifted into position. A number of factors need to be considered to achieve this such as crane capacity and reach, the availability of lifting beams or the possibility of installing secondary trusses through the roof beam lines for stability.

Can I retro-fit a tie bar on my installed roof?

Retro-fitting a tubular tie bar to a previously installed roof is difficult. For this reason we always recommend the tie tube system is installed at ground level where the roof can be lifted and lowered to ensure hole alignment and an easy fit of the elements. A tension cable can be installed following roof installation, we recommend our connection plates are pre-installed prior to roof bay installation to provide a solid connection point for the tension cables.

How can I terminate my excess sheet length?

There are a series of ways to achieve this, all of which are documented in the user guides. Excess sheets can be secured to the scaffold or returned into the roof space.

My roof is leaking, why?

If built correctly and subject to normal weather conditions, our roofs are leak free. A number of factors can cause leaks such as:
• Monopitch roofs built at an insufficient angle.
• Damaged components such as tracking ends and tracking spigots thereby not creating a seal at tracking joints.
• Incorrect installation procedure followed.
• Inadequate sheet tension.
• Supports not level introducing a twist into the roofing bays.
It should be noted that use of DeepFlow™ profile eliminates the possibility of leaks.

Do DESSA provide any anchoring solutions?

We provide a variety of components that can provide anchors such as bolted top plates and offset shear anchors. We also provide design and manufacture services on any component to achieve the desired anchor solution.

Can UNI Roof bracing be used for lacing and bracing of beams?

Complimentary lacing and bracing kits can be obtained for a number of our beam series. Use of these kits minimise weight and assembly times.

How can I work out the erection time of a roof?

As a general rule of thumb, you can expect four experienced operatives to achieve 250m2 in the first day of operation, with 400m2 each following day.

How do we seal the gap between sheet and ground when terminating a sidewall sheet?

Sheets can be fitting with “mud flaps” which provide additional coverage outside of the tensioning line. Our plastic Keder profile is ideal for sealing the Keder flaps to each other.

Do DESSA provide components to continue roof sheeting down the outside standard of a scaffold?

We provide a series of tracking couplers to achieve this. These connect to standards or ledgers to provide connection points for vertical or horizontal sheet tracking.

Do DESSA provide coloured sheets?

We can provide sheeting in a wide range of colours. For a specific colour please contact us via our online form or contact info@altrad-dessa.com.

Why use DESSA’s sheet tensioning bar instead of scaffold tube?

The tension bar features pre-drilled holes for locating the sheet pulling bar assembly and is colour-coded for easy recognition on site.

What sheeting types do DESSA offer?

DESSA offers three main types of roof sheet:
• 360 gsm for light-weight single use operations.
• 610 gsm standard offering.
• 910 gsm for heavy duty requirements.
These can be supplied in roof sheets, valance sheets, gable sheets, wall sheets and so on.

I want to build a rolling roof, what are my options?

We offer a multitude of runway and castor options. sysTRAX™ and TRAX UB can be used as a heavy duty solution with integrated anti-uplift. Trax tube holder can be used to make best utilisation of scaffold tube and fittings.

Do you supply guttering for your roofs?

No. We supply a gutter support bracket to enable a timber eaves board to be installed along the length of the roof to which off-the-shelf rainwater goods can be used. Gutter sizing is subject to calculation and can vary according to duration, location, inclination and down-pipe frequency. Gutter design should be verified by a competent Engineer.