Kingspan Therma TR26 on a lightweight industrial roof

Number the rooflights on the plan and measure each type of kerb from a common datum. On a roof with falls, identify the side where the finished surface comes up highest. This is where the least height remains for the flashing upstand.

Select one such rooflight as a trial bay. Its section should show the supporting deck, horizontal and vertical insulation, and termination of the waterproofing upstand. Check how the cut edges are supported at the actual opening before repeating the detail.

The Polish Therma catalogue gives a minimum compressive stress of 120 kPa at 10% deformation for TR26. To determine pressure beneath a plant support, obtain the support reaction and contact area. The designer then checks how the force travels through the roof layers into the structure.

For a ballasted roof, show the ballast weight and distribution on the plan. For a mechanically fixed roof, specify fasteners to suit the deck and wind loading. Take the product reaction-to-fire class from the declaration for the supply in question and check the whole-roof requirements against the assembly documentation.

At a declared conductivity of 0.022 W/(m·K), a 100 mm TR26 board has a thermal resistance of 4.50 m²K/W. At 140 mm it reaches 6.35 m²K/W. With the same deck level, this raises the top of the insulation by 40 mm alongside the rooflight as well.

Mark both levels on the section and compare the remaining upstand heights with the selected system requirements. Include the other layers and the effect of fixings in the roof U-value. Assess the thermal junction with the vertical kerb insulation at its actual location.

Draw the opening spacing, support widths and joint lines first. Overlay board outlines of 1200 × 2400 or 1200 × 600 mm. Check size and edge availability for the thickness ordered, particularly for the 85 mm option.

Distinguish strips retaining a factory edge from strips cut on both sides. On a profiled metal deck, check where each strip bears on the crowns. Measure the gap between adjacent kerbs once both rooflights are in their final positions.

At a ventilation duct, mark the seal to the vapour control layer below the board and the seal to the roof membrane above it. TR26 has an aluminium-containing facing on each side. Bringing its cut edge up to the duct still leaves both specified seals to be installed.

Time inspections to match access to each layer. Inspect the lower collar before the insulation conceals it. After waterproofing, check the upper upstand and water path around the base. Label photographs from both stages with the penetration reference on the services drawing.

Measure boards by coverage and cutting layout, and junctions by length and item count. Five identical rectangular rooflights with 2 × 3 m bases give 50 m of perimeter flashing before allowances. Count corners separately and allow material for laps.

Include the numbered rooflight plan and the section at the lowest kerb in the enquiry. Ask for the fixings, vertical insulation and flashings included for each type. Differences between quotations can then be traced to a dimension or an identifiable item of work.