Plain Half Round Cast Aluminium Guttering

Cast aluminium Gutters have become the widely accepted alternative to Cast Iron and are now a first choice owing to their lightweight, corrosion resistant, low maintenance and aesthetically pleasing characteristics. Our 'Legacy' Plain Half Round Aluminium Gutters are available in a variety of sizes including 100mm (4 Inch) Half Round, 114mm (4.5 Inch) Half Round, 125mm (5 Inch) Half Round and 150mm (6 Inch) Half Round. Cast aluminium is available in mill finish or can be painted by powder coating in a variety of colours.


The Plain Half Round Cast Aluminium Gutters come in various sizes (100mm,114mm, 125mm & 150mm) & are supplied with a complete range of accessories ie angles, outlets, stopends, fascia brackets. True and Facetted radius gutters are also available.


Aluminium Cast Half Round Gutters have fascia brackets which are set out at 915mm maximum centres no further than 300mm from a joint or fitting. The fascia brackets should be set out to any pre-determined fall taking note of the position of any fittings such as outlets and angles beforehand, brackets should be fixed using 5mm x 25mm stainless steel countersunk screws (dependant on substrate).See Fig 1.
Rafter brackets are also available whose centres may be governed by the roof timbers. Rise and fall brackets driven into the masonry are recommended to be at 915mm maximum centres.
Fig 1.


Aluminium has a coefficient of expansion equal to 0.00002348mm per °C on average, this equates to just over 1.4mm per metre on a temperature range of -20°C to +40°C. Typically a 3mm to 4mm expansion gap between the ends of the gutter sections is advisable.

ARP recommend and supply Arbosil 1096 Low Modulus Silicone sealant and it is essential that this or a direct equivalent is used to seal the joints as this will ensure a strong mechanical bond that withstands the forces associated with thermal movement.
It is important to observe the sealant manufacturers guidelines concerning application and curing during cold or damp weather conditions & that before assembling the joint all surfaces are clean & free from grease, acetone applied with a soft cloth and wiped dry is recommended.

Cast Half Round gutters have a Spigot and Socket overlap arrangement that are secured using M6 x 30mm aluminium bolts, neoprene washers and nuts.
Having sited the gutter, apply 2 x 6mm beads of Arbosil 1096 Low Modulus Silicone sealant to the gutter socket. (Fig 2.) The two surfaces can then be brought together, the bolt inserted applying sealant to the thread and round the slot in the union, tighten the joint until some sealant emerges and a feeling of resistance is achieved leaving a 3mm sandwich of sealant. Excess sealant should then be removed.

Fig 2.

Composition and Manufacture:

‘Legacy” Cast Half Round Gutters are manufactured from Aluminium alloy LM27 to BS1474: 1972 & the product complies to, or exceeds all relevant standards.
Special fittings for the gutters using fabrication methods involving cut, mitre and welding techniques can be provided.


Mill Finish Aluminium or Polyester Powder Coated to a range of BS or RAL Colours

Model Specification:

ARP heavy grade ‘Legacy’ Gutters and fittings to BS 2997 (EN612) using LM27 alloy aluminium in accordance with BS1474: 1974. Profile to be Half Round, size 100mm (3mm),114mm (3mm), 125mm (4mm) & 150mm (4mm). Materials to have factory applied Polyester Powder Coat to all significant surfaces in accordance with BS EN 122026 Matt/Satin/Gloss* finish, or alternatively plain aluminium Mill Finish. All to be supplied by Aluminium Roofline Products Ltd, Unit 2, Vitruvius Way, Meridian Business Park, Braunstone, Leicester LE19 1WA. Tel 0116 2894400 Fax 0116 2894433.
Joints to be loose union connector sealed by application of Arbosil 1096 Low Modulus Silicone Sealant and fastened by M6 x 30mm bolts, neoprene washers and nuts in accordance with the manufacturer’s specification and guidelines. Gutter to be fixed by fascia brackets at 915mm centres with supplementary brackets at or near fittings. Fixing for brackets to be 5mm x 25mm countersunk/domed head stainless steel screws (dependant on substrate).

Legacy Plain Half Round Cast Aluminium Technical Guide