Can T14 profiled steel sheet be used to reroof or enclose an open-sided shelter?

Consider any change in use. Closing the sides of an open shelter changes the wind pressures on it. Conversion to a heated workshop also calls for a design that deals with heat and moisture. The T14 sheet addresses only part of that brief. It provides neither thermal insulation on its own nor a complete building envelope.

The number refers to the nominal profile depth. It does not specify all dimensions or permissible loads. One version has a depth of 14 mm, an effective cover width of 1,120 mm and an overall width of 1,157 mm. It is offered in thicknesses from 0.5 to 0.7 mm. Other profiles in this group can have different dimensions.

For that particular profile, recommended sheet lengths reach 6 m in 0.5 mm steel and 7 m in 0.7 mm steel. These figures apply only to that version. Sheet length is distinct from the unsupported span. A long sheet generally bears on several supports.

The original sheeting may have had a different profile, thickness or fixing pattern. Years of service do not establish the suitability of a replacement. Assess snow and wind loads, the spans and their arrangement. Identify the bearing width and the material into which the screws will be driven. Complete this assessment before ordering, since changing supports after delivery can mean cutting the sheets again.

Use the load table for the exact sheet specification. Check strength and deflection separately. The highest number in the table may describe a different support arrangement. If the structure and sheet are incompatible, the designer can change the supports or specify different sheeting. Adding screws alone does not resolve a span problem.

Use the effective cover width to set out the sheets. On a slope 6.40 m wide, six runs at 1.12 m give 6.72 m of cover, so the edge sheet needs trimming. At a sheet length of 4.20 m, the order represents 28.224 m² of effective coverage. The rectangular roof surface itself measures 26.88 m² before any required projections.

This calculation distinguishes roof area from the quantity of sheet to buy. It does not size the laps or the eaves projection. When setting out the actual roof, allow for uneven edges, flashings and the installation instructions for the chosen profile. Measure both sides of the slope. Opposite edges on an old shelter are not always the same length.

Before installation, trace the route rainwater will take from ridge to gutter. Minimum pitch and lap lengths depend on the specified covering. Pay particular attention to end laps and wall abutments. Flashings should shed water without trapping it or directing it under the roof. Sealant cannot compensate for sheets installed in the wrong sequence.

In an unheated shelter, condensation can form on the underside of the roof. Suitable ventilation and a roof build-up designed for the conditions help limit it. Anti-condensation fleece can temporarily retain some moisture but needs an opportunity to dry. Enclosing the sides can change those drying conditions. Allow for this before the renovation.

Select the coating for the exposure. A sheltered garden and a site near aggressive fumes or pollutants present different conditions. Remove swarf and installation debris when the work is finished. Steel particles left on the sheet can rust and stain an otherwise intact coating.

Keep a record of the profile geometry, thickness and colour. The T14 designation alone is insufficient to match a replacement sheet later. Inspect flashings, fixings and drainage paths periodically. Plan safe access for inspections. Do not assume every part of thin sheet roofing can take a person’s weight.