POWERDECK B

Description

Powerdeck B is a CFC & HCFC-free insulation board with a rigid polyisocyanurate foam core. The insulation board is faced with a mineral coated glass fleece on the reverse side and a bituminous glass fleece with a polypropylene film on the top surface. The boards must be installed with the bituminous facing uppermost.

Design

Built-up Felt Waterproofing Systems

Powerdeck B boards are compatible with most torch-on, bituminous built-up felt roofing systems. Built-up felt systems are laid partially bonded, in conjunction with a type 3G felt venting layer, directly on to the boards in accordance with BS 8217.

Condensation

A suitable vapour control layer must be installed prior to laying the Powerdeck B boards. This can be in the form of a single layer of Type 3B roofing felt. Reference should be made to BS 5250 and BS 6229 for the condensation assessment and adequate bonding to the deck.

Roof Loading

Powerdeck B boards are suitable for loads associated with the pedestrian maintenance traffic on the roof; for areas of heavier pedestrian traffic extra precautions should be taken such as the use of promenade tiles. Care must be taken to avoid damage to boards by impact or by concentrated loads during installation.

Roof Drainage

To ensure adequate drainage the roof should have a minimum finished fall of 1:80. This may mean designing for twice the minimum finished fall to account for building inaccuracies, roof deflection and building settlement.

Thermal Bridging

With increasing levels of insulation it is vitally important to ensure continuity of the insulation at the junction of elements. At the junction of the roof and the wall packing the eaves with compressible mineral fibre insulation will both prevent thermal bridging and close the cavity.

At upstands and parapets the cavity wall insulation should be continued above the level of the roof to ensure continuity of the wall and roof insulation.

Wind Uplift

The wind uplift force exerted on the roof will vary according to geographical location, site location and building height. Reference should be made to BS 6229 for adequate bonding of the vapour control layer to the deck to help resist wind uplift. Calculations relating to the bonding and any supplementary fixings should be made with reference to BS 6399.

Fire Performance

When used within a flat roof constructed in accordance with this brochure Powerdeck B will not prejudice the fire resistance properties of the roof and adds no significant fire load to the building. A 3 layer built-up felt covered with 10mm chippings would give the required external fire rating, FAA: whilst 12.5mm plasterboard will ensure the necessary fire protection internally. For other specifications the manufacturer of the mineral surfaced cap sheet should be contacted. Fire stopping in the form of mineral fibre insulation should be used at party walls.

Installation

Timber Deck

The usual procedure for construction is:

1. A vapour control layer, normally Type 3B felt, is either fully bonded in hot bitumen or nailed to the plywood deck. On tongue and groove timber decks the vapour control layer should be nailed. Ensure a 50mm overlap at the end and side laps and seal around penetrations and openings. At roof edges, parapets, abutments etc allow sufficient extra felt to either lap back on top of the insulation or to dress into the upstand by at least 150mm.

2. Hot bitumen is mopped over the vapour control layer and the Powerdeck B boards bedded into it, with the bituminous face uppermost, in a brick-bond pattern. Suitable polyurethane based adhesives may also be used to bond the boards to the vapour control layer.

3. Alternatively the Powerdeck B boards may be mechanically fixed using screw fixings incorporating a 75mm diameter washer within 50mm to 150mm of each corner. Additional fixings may be required in areas of especially high wind loads or around the perimeter of the roof where the wind uplift is greatest.

4. The vapour control layer should be turned back over the top of the boards and sealed in hot bitumen.

5. A Type 3G felt perforated base layer is then loose laid, mineral surface down, on the insulation.

6. The next two layers of high performance roofing felt are then torched on.

7. To prevent moisture ingress into the system during installation lay only sufficient Powerdeck B boards that can be waterproofed in the same working period. Correctly seal and weather any joints or edges at the end of the day’s work.

Metal Deck

The usual procedure for construction is:

1. The metal deck must be primed prior to laying the vapour control layer.

2. The vapour control layer, normally Type 3B felt, is bonded in hot bitumen to the deck. Ensure a 50mm overlap at the end and side laps and seal around penetrations and openings. At roof edges, parapets, abutments etc allow sufficient extra felt to either lap back on top of the insulation or to dress into the upstand by at least 150mm.

3. Hot bitumen is mopped over the vapour control layer and the Powerdeck B boards bedded into it, with the bituminous face uppermost, in a brick-bond pattern. Suitable polyurethane based adhesives may also be used to bond the boards to the vapour control layer.

4. Alternatively the Powerdeck B boards may be mechanically fixed using fixings incorporating a 75mm diameter washer within 50mm to 150mm of each corner. Additional fixings may be required in areas of especially high wind loads or around the perimeter of the roof where the wind uplift is greatest.

5. The boards should be laid either with their long edges across the troughs or diagonally across the roof to ensure that the short ends are fully supported (see table below).

6. The vapour control layer should be turned back over the top of the boards and sealed in hot bitumen.

7. A Type 3G felt perforated base layer is then loose laid, mineral surface down, on the insulation.

8. The next two layers of high performance roofing felt are then torched on.

9. To prevent moisture ingress into the system during installation lay only sufficient Powerdeck B boards that can be waterproofed in the same working period. Correctly seal and weather any joints or edges at the end of the day’s work.

Spanning On Metal Decks

Powerdeck B Thickness (mm)

Maximum Span (mm)

30

100

40

150

45

175

50

200

Concrete Deck

The usual procedure for construction is:

1. The deck must be dry, clean, smooth and laid to the correct fall.

2. The deck must be primed prior to laying the vapour control layer, normally Type 3B felt, bonded in hot bitumen to the deck. Ensure a 50mm overlap at the end and side laps and seal around penetrations and openings. At roof edges, parapets, abutments etc allow sufficient extra felt to either lap back on top of the insulation or to dress into the upstand by at least 150mm.

5. The vapour control layer should be turned back over the top of the boards and sealed in hot bitumen.

6. A Type 3G felt perforated base layer is then loose laid, mineral surface down, on the insulation.

7. The next two layers of high performance roofing felt are then torched on.

8. To prevent moisture ingress into the system during installation lay only sufficient Powerdeck B boards that can be waterproofed in the same working period. Correctly seal and weather any joints or edges at the end of the day’s work.

Heat Loss Calculations

The tables below gives typical U-values that may be achieved when using Powerdeck B on timber, metal and concrete decks.

Timber Deck with Plasterboard Ceiling

Powerdeck B Thickness (mm)

U-Value (W/m²K)

30

0.57

40

0.47

50

0.40

60

0.35

70

0.30

80

0.27

90

0.25

100

0.23

120

0.19

140

0.17

150

0.16

Metal Deck no Ceiling

Powerdeck B Thickness (mm)

U-Value (W/m²K)

30

0.69

40

0.55

50

0.45

60

0.38

70

0.34

80

0.30

90

0.27

100

0.24

120

0.20

140

0.18

150

0.17

Concrete Deck (150mm) with Plasterboard Ceiling

Powerdeck B Thickness (mm)

U-Value (W/m²K)

30

0.59

40

0.48

50

0.41

60

0.35

70

0.31

80

0.28

90

0.25

100

0.23

120

0.19

140

0.17

150

0.16

Specification Clause

The flat roof insulation shall be minimum ....... mm thick Recticel Powerdeck B CFC and HCFC-free, rigid PIR foam with a top face of bituminous glass fleece (with a polypropylene film) and a reverse face of mineral coated glass tissue. The boards to be manufactured to BS EN 13165 and quality assured to BS EN ISO 9001. Insulation to be installed as work proceeds in accordance with Recticel Insulation Products instructions