Cassettes

The ever-increasing thermal performance and building quality standards, coupled with the continuous demand for housing and the shortage of skilled labour have led to a resurgence of timber framed house construction, much of this being of the large wall panel type, and including floor cassettes, i.e. completely manufactured large floor panels for crane construction incorporating all joists, blockings, holes for

2 x 12 mm fermacel

Counter batten 22 mm Bitroc

Insulation Full nogging

47 x 197 smartroof joist

Site nailed as detail 'a'

12 mm smartroof plywood/OSB

Smarttongue

35 x 72 smartchannel

Smartroof spandrel double 36 x 97

2 x 12 mm fermacel

Fig. 4.13a Cassette roof - standard panel to party wall spandrel fixing.

Standard panel

CX"

d

S5"

212 mm

S7.5"

214 mm

40"

21B mm

42.5"

222 mm

45"

227 mm

Q 12 mm structural board

© Panel core - standard 197 mm

@ Panel closer board - standard 22 mm

(5 Roofing felt

(6 Battens and tiles as traditionally

© Felt dresses over fascia - fillet as required

® Soffit width - as required

@ Structural overhang - standard 36 x 72

Fig. 4.13b Cassette roof - eaves setting out.

Timber purlins

Ventilated ridge slate/tile by others Ridge batten -

uPVC profile filler unit

0.7 mm thick plastisol coated batten support plate fixed to external weather sheet with two fasteners

Roof slates/tiles system including battens by others

Internal ridge flashing complete with Alfasbond FR canister applied insulation for thermal continuity uPVC profile filler unit

0.7 mm thick plastisol coated batten support plate fixed to external weather sheet with two fasteners

Roof slates/tiles system including battens by others

Internal ridge flashing complete with Alfasbond FR canister applied insulation for thermal continuity

Internal PPC galv. steel ridge support with Air seal - Vapourflex

'Air seal - 8 mm 0 butyl rubber sealant

KS1000 TS

Insulated roof panel

Fig. 4.14a Ridge details.

Timber purlins |nternal closure feshiing with 1°° mm R00f tile system including battens by others laps air sealed with gun-grade sealant .

Air seal - 8 mm 0 butyl rubber sealant KS1000 TS insulated roof panel

9 x 3 mm butyl rubber seal Closure flashing with 150 mm sealed butt straps Canister applied insulation

Fascia board by others

Timber purlin

Km&parl

Fig. 4.14b Verge details.

Air seal - continuous bead of gun-grade sealant

Timber purlin

Km&parl

Fig. 4.14b Verge details.

services and prefixed weatherproofed deckings. The factories making these lend themselves ideally to manufacturing roof cassettes. The crane for the erection of these large roof cassettes is already on site having assembled the timber framed house or lowered the floor cassette on to a traditional constructed building. Most of these systems therefore come from timber framed housing manufacturers.

Tradis is one such cassette developed as part of a whole house construction system. It uses engineered 'Masonite' I beams with a ceiling and roof decking sheathing to form a stress skin panel filled with highly efficient insulation. The product is sophisticated in its thermal and vapour control technology and claims highly 'green' credentials. The method provides an instantly weathertight (except for any roof windows or dormers that need to be constructed) roof shell, thus allowing internal working to proceed before tiling is complete. Tradis is manufactured by Excel Industries Ltd. See bibliography for details.

smartroof® is different to the above system in that it spans from gable to gable or some internal cross wall support, i.e. a partition or principle truss. The system consists of stress skin interlocking panels designed to key to the design detail on the timber framed gable panels. The ply ceiling panels are pattern nailed to stress graded trussed rafter type machined timbers, the voids filled with insulation to client specification, which can include environmentally friendly sheep's wool (a commercially available product) and conventional mineral wool. The cassette is sheathed externally with a vapour breathable board, i.e. a structural sarking. Panels have a simple interlocking detail between them connected by nailing to an approved pattern. Openings in this type of cassette, because it is spanning from gable to gable or principal to gable, can provide windows almost the entire width of the roof. It therefore offers greater freedom of roof window location than the ridge to eave cassette options. Figure 4.13 illustrates a smartroof panel anchorage method to the spandrel or gable timber framed panel, and shows a typical eaves detail. Both illustrations are taken from the smartroof technical manual. smartroof is the proprietary name of smartroof Ltd, full details of which can be found in the bibliography.

Kingspan is yet another cassette design which is part of a whole roof system including lightweight tiles. It is suitable for all types of building including domestic, commercial and public buildings, and can be fitted to either steel framed or traditional timber roof structures. The panels are comprised of a ridged foam insulation sandwiched between thin plastic coated steel profiled sheets which give the strength to the cassette. The insulation core can vary from 40 mm to 100 mm. With the foam lower than the cassette ribs, there is good provision for ventilation. Typical details of this method can be seen in Fig. 4.14 which shows a ridge for a purlin roof structure showing the ceiling system and ventilation. Also illustrated is a verge detail suitable for domestic buildings where purlins are used as the structure. Kingspan's technical literature illustrates numerous other ridge, eaves, verge, valley and abutment details.

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