Choosing Gutters & Downpipes
A well-designed rainwater system has a simple but extremely important job: collecting water from the roof and safely carrying it away from the building.
Roundtower supplies both cast iron and cast aluminium rainwater systems, providing options for traditional buildings, conservation work, renovation and new construction.
The best material depends on the building, architectural requirements, exposure, maintenance expectations and practical considerations during installation.
Cast Iron or Cast Aluminium?
Both materials can reproduce the traditional appearance associated with period rainwater goods, but their characteristics are different.
Cast iron provides the weight, rigidity and authentic material character of traditional historic rainwater systems.
Cast aluminium provides a similar traditional visual appearance but is substantially lighter and naturally resistant to rust, making installation and ongoing maintenance easier.
Neither material is universally better. The correct choice depends on the priorities of the particular project.
Why Choose Cast Iron?
Cast iron has been used for rainwater systems for generations and remains particularly appropriate where retaining or reproducing traditional rainwater detailing is important.
Advantages include:
- traditional material and appearance;
- high strength and rigidity;
- substantial architectural character;
- very long potential service life;
- wide choice of historic gutter profiles;
- availability of matching hoppers and fittings;
- repairability and repaintability;
- and suitability for bespoke cast components.
Correctly installed and maintained cast iron rainwater goods can provide an exceptionally long service life.
Hargreaves Cast Iron Rainwater Systems
Roundtower supplies Hargreaves Premier cast iron rainwater goods.
The Premier range includes traditional gutters, pipes, fittings and hopper heads manufactured for complete cast iron rainwater installations.
A broad range of standard components is available, while bespoke castings can also be produced where unusual architectural details need to be reproduced.
This makes cast iron particularly useful where an existing historic rainwater system contains profiles or decorative details that cannot be readily replaced with standard modern products.
Traditional Cast Iron Gutter Profiles
The Roundtower cast iron range includes a number of traditional gutter profiles, including:
- Half Round;
- Beaded Half Round;
- Deep Style Half Round;
- OG;
- Notts OG;
- moulded profiles;
- and Box Guttering.
The correct profile should be selected according to both the architectural character of the building and the drainage capacity required.
Where an original gutter survives, its dimensions and profile can often provide the best starting point for selecting a suitable replacement.
Cast Iron Downpipes
Cast iron downpipes are available in traditional round, square and rectangular configurations, together with the bends, branches, sockets, offsets, shoes and fixing components required to create a complete system.
Eared and plain pipe arrangements allow the downpipe installation to be adapted to different fixing requirements and architectural styles.
Matching the scale of the downpipe to the gutter and overall building façade helps create a balanced finished appearance.
Cast Iron Hopper Heads
Hopper heads provide a collection point at the top of a downpipe.
They can receive rainwater from:
- gutter outlets;
- parapet outlets;
- flat roofs;
- valleys;
- balconies;
- and other drainage points.
Roundtower supplies a dedicated range of Hargreaves Cast Iron Hopper Heads, including restrained traditional designs and more decorative architectural styles.
Hopper heads can become an important visual feature of a traditional façade as well as performing their rainwater collection function.
Why Choose Cast Aluminium?
Cast aluminium provides an alternative where a traditional rainwater appearance is wanted without the weight and maintenance characteristics of cast iron.
Advantages include:
- significantly lower weight;
- easier handling on site;
- corrosion resistance;
- durable powder-coated finishes;
- low maintenance requirements;
- traditional profiles;
- a wide selection of colours;
- and suitability for both traditional and contemporary architecture.
Its reduced weight can be particularly useful where installation access is difficult or where handling heavy cast iron components would be impractical.
Traditional Appearance with Lower Weight
Cast aluminium rainwater goods are designed to reproduce the substantial appearance of traditional cast systems rather than looking like lightweight extruded or plastic guttering.
This makes them particularly useful where architectural appearance matters but genuine cast iron is not essential to the project.
The lower weight also reduces the physical demands associated with transporting, lifting and positioning long gutter and downpipe sections.
Cast Aluminium Gutters
Roundtower supplies traditional cast aluminium gutter profiles including Half Round systems, together with outlets, angles, stop ends, brackets and joint connectors.
Different gutter sizes allow the system to be selected according to the roof drainage requirement.
The complete gutter arrangement should be considered rather than selecting a profile purely by appearance.
Cast Aluminium Downpipes
The Heritage cast aluminium range includes collared circular rainwater pipes designed to reproduce traditional cast downpipe detailing.
Matching components include:
- bends;
- offsets;
- shoes;
- collars;
- and associated fittings.
This allows the downpipe to be configured around architectural projections while maintaining a consistent traditional appearance.
Cast Aluminium Finishes
Cast aluminium rainwater goods are supplied with durable protective powder-coated finishes.
A broad selection of standard colours is available, together with additional RAL and BS colour options for appropriate projects.
This allows the rainwater system to be coordinated with:
- windows;
- doors;
- painted façades;
- roof finishes;
- architectural metalwork;
- and other exterior details.
Black remains a popular traditional choice, but it is not the only option.
Choosing a Gutter Profile
Gutter selection should consider both appearance and hydraulic capacity.
A smaller profile may suit the proportions of a modest cottage, while larger roof areas can require gutters with greater capacity.
Factors influencing selection include:
- roof area;
- roof pitch;
- rainfall intensity;
- gutter length;
- number and position of outlets;
- gutter profile;
- downpipe diameter;
- and the architectural scale of the building.
Where the roof drainage requirement is substantial, the system should be sized rather than simply copied from a visually similar installation.
Gutter Size Matters
Increasing the size of only one component does not necessarily solve a rainwater-capacity problem.
The complete path of the water should be considered:
roof
→ gutter
→ outlet
→ hopper where used
→ downpipe
→ drainage system
A restriction at any one point can limit the capacity of the complete system.
Downpipe Sizing
Downpipe diameter needs to be appropriate for the amount of water reaching it.
A large gutter connected to an undersized outlet or downpipe can still overflow during intense rainfall.
Similarly, increasing the downpipe diameter will not compensate for an inadequately sized gutter or restricted outlet.
For larger or more complicated roofs, appropriate rainwater calculations should be carried out.
Why Rainwater Goods Matter on Traditional Buildings
Gutters and downpipes are particularly important on traditional solid masonry buildings.
Stone, brick and lime mortar can absorb liquid water.
A leaking gutter, blocked hopper or fractured downpipe can concentrate large quantities of roof water onto a relatively small section of wall.
Repeated wetting can contribute to:
- saturation of masonry;
- deterioration of pointing;
- staining;
- frost-related deterioration;
- timber decay where embedded timber becomes wet;
- and deterioration of internal finishes.
Maintaining an effective rainwater system is therefore an important part of managing moisture in older buildings.
Gutters & Lime-Rendered Walls
Defective gutters can be especially damaging where water repeatedly runs down a rendered façade.
Even a vapour-permeable lime render is not intended to continuously receive concentrated roof drainage.
Before repairing deteriorated render, gutters, outlets, hoppers and downpipes should therefore be inspected for defects that may be contributing to excessive wetting.
Gutters & Stone Buildings
Open-jointed stonework can absorb substantial amounts of rainwater where gutters are overflowing or downpipes are leaking.
Repairing the rainwater system can sometimes be one of the most important interventions before repointing or internally upgrading an older masonry wall.
The objective should be to manage the source of unnecessary water, rather than expecting the wall finish alone to accommodate persistent rainwater leakage.
Cast Iron for Conservation Work
Cast iron is often selected for restoration projects because it reproduces both the material and appearance of traditional rainwater systems.
Where original cast iron survives, consider retaining serviceable components where practical.
Existing gutters and pipes can also provide valuable information about:
- original profile;
- dimensions;
- fixing arrangements;
- outlet locations;
- hopper design;
- and decorative details.
Where exact replacement is important, bespoke cast components may be possible.
Cast Aluminium for Traditional Buildings
Cast aluminium can also be appropriate where a traditional appearance is required but lower weight and reduced maintenance are priorities.
It can be particularly useful for:
- renovation;
- extensions to traditional buildings;
- sympathetic new construction;
- inaccessible rooflines;
- and projects where traditional-looking rainwater goods are desired without specifying cast iron.
For protected structures or architecturally significant buildings, the proposed material and profile should be agreed as part of the project specification rather than assuming one rainwater material will automatically be accepted.
Conservation & Protected Structures
There is no single gutter or downpipe product that is automatically appropriate for every protected or historic building.
Selection may depend on:
- surviving original materials;
- architectural significance;
- existing profiles;
- planning or conservation requirements;
- and the proposed extent of alteration.
Where original cast iron rainwater goods form an important part of the building's character, retaining cast iron may be preferable to substituting another material.
Coastal Locations
Coastal exposure places additional demands on external metalwork.
Cast iron relies on its protective coating system, which should be correctly specified and maintained according to the exposure conditions.
For exposed coastal projects, enhanced coating specifications may be appropriate.
Cast aluminium provides good inherent corrosion resistance, but its finish and fixings should still be suitable for the environmental exposure.
No external rainwater system should be regarded as maintenance-free simply because it is installed in aluminium.
Cast Iron Finishes
Cast iron rainwater goods can be supplied with different factory finishes depending on the specification.
Where products are supplied in a transit primer, an appropriate finishing paint system needs to be applied.
Factory-finished options can reduce the amount of finishing required on site.
The coating should then be inspected periodically and repaired if damaged.
Maintaining Cast Iron Gutters
Cast iron is extremely durable, but its protective coating requires periodic maintenance.
Maintenance should include:
- clearing leaves and debris;
- checking outlets;
- inspecting gutter joints;
- checking brackets and fixings;
- inspecting painted surfaces;
- repairing damaged coatings;
- and ensuring downpipes remain clear.
Early maintenance of a small coating defect is considerably preferable to allowing corrosion to become established.
Maintaining Cast Aluminium Gutters
Cast aluminium generally requires less coating maintenance than cast iron, but it still benefits from periodic inspection and cleaning.
Check for:
- leaf and debris accumulation;
- blocked outlets;
- joint failure;
- loose brackets;
- damaged powder coating;
- and blocked downpipes.
Any coating damage should be dealt with using a compatible repair system.
Cleaning Gutters
Leaves, moss and other debris can significantly reduce gutter capacity.
The problem is particularly common where buildings are surrounded by mature trees.
Gutters and hopper heads should therefore be inspected and cleaned periodically, especially before periods of heavy autumn and winter rainfall.
Maintenance frequency should reflect the particular building and its surroundings.
Gutter Brackets & Supports
The gutter needs adequate support to maintain the required alignment and falls.
Different systems use different bracket arrangements including:
- fascia brackets;
- rise-and-fall brackets;
- rafter brackets;
- and specialist support details.
Bracket type and spacing should follow the requirements of the selected rainwater system.
The supporting building fabric also needs to be capable of carrying the chosen system, particularly where heavy cast iron gutters are installed.
Downpipe Offsets
Roof overhangs, cornices and architectural features often mean a downpipe cannot simply run vertically from the gutter outlet to ground level.
Offsets and bends allow the pipe to negotiate these projections while maintaining a continuous drainage path.
The number and geometry of bends should be considered carefully, as unnecessary complexity can make the system more difficult to clean and maintain.
Downpipe Shoes
A downpipe shoe directs water away from the bottom of the pipe where an open discharge arrangement is used.
Where the downpipe connects into underground drainage, the appropriate connection detail should be used instead.
Rainwater should not simply be discharged against the base of a traditional masonry wall.
Matching Existing Rainwater Goods
Where an existing system is being repaired or extended, useful information includes:
- gutter profile;
- gutter width and depth;
- downpipe diameter;
- pipe shape;
- overall dimensions;
- bracket arrangement;
- outlet positions;
- existing finish;
- and photographs of surviving fittings.
Roundtower can use this information to help identify suitable replacement components.
Bespoke Rainwater Goods
Historic buildings do not always conform to modern standard dimensions.
Where standard products cannot reproduce an existing feature, bespoke rainwater components may be available.
These can include:
- special gutter angles;
- radius gutters;
- unusual offsets;
- bespoke brackets;
- and decorative hopper heads.
Bespoke manufacture can be particularly valuable where important original architectural detailing needs to be retained or reproduced.
Mixing Cast Iron & Cast Aluminium
As a general approach, it is preferable to use a consistent rainwater system rather than mixing cast iron and cast aluminium components within the same run.
The two materials have different weights, jointing details, thermal behaviour and finishing systems.
Keeping gutters, outlets, downpipes and fittings within a coordinated system simplifies specification and installation and usually gives the most consistent finished appearance.
Frequently Asked Questions
What types of gutters does Roundtower supply?
Roundtower supplies cast iron and cast aluminium rainwater systems, including gutters, downpipes and the associated fittings required to create a complete installation.
Which is better, cast iron or cast aluminium?
Neither is universally better.
Cast iron offers genuine traditional material character and exceptional longevity, while cast aluminium is considerably lighter, corrosion resistant and generally requires less maintenance.
Is cast iron suitable for old buildings?
Yes, particularly where traditional cast iron rainwater goods already exist or where authentic material and detailing are important.
The requirements of significant historic or protected buildings should still be considered individually.
Is cast aluminium suitable for traditional buildings?
Yes, where its appearance and specification are appropriate to the building.
It can provide a traditional cast appearance while being lighter and easier to maintain than cast iron.
How long can cast iron guttering last?
Correctly installed and maintained cast iron rainwater systems have a proven service history extending beyond 100 years.
Periodic inspection and maintenance of protective coatings remain important.
Does cast aluminium rust?
Aluminium does not rust in the same way as iron.
It is corrosion resistant, although the powder-coated finish, joints and fixings should still be maintained appropriately.
Do cast aluminium gutters need maintenance?
Yes.
They generally require less maintenance than painted cast iron, but gutters should still be cleaned and inspected periodically and any damaged finish repaired.
What gutter profiles are available?
Roundtower's rainwater range includes traditional profiles such as Half Round, Beaded Half Round, Deep Half Round, OG, moulded and box-style gutters, depending on material and system.
Do you supply matching downpipes?
Yes.
Roundtower supplies matching downpipes and fittings including bends, offsets, shoes, branches, collars and fixing components.
Do you supply cast iron hoppers?
Yes.
Roundtower has a dedicated range of Hargreaves cast iron hopper heads in traditional and decorative designs.
How do I know what size gutter I need?
Gutter sizing depends on roof area, rainfall intensity, roof pitch, gutter profile, outlet arrangement and downpipe capacity.
Larger or more complicated roofs may require formal rainwater calculations.
Are gutters important for damp control?
Correctly functioning rainwater goods are extremely important for limiting unnecessary wetting of external walls.
They do not make a wall waterproof, but they prevent roof water from being repeatedly concentrated onto the masonry.
Can you match an existing gutter?
In many cases, yes.
Send Roundtower photographs and dimensions of the existing gutter, downpipe or hopper and we can help identify the closest available profile or investigate bespoke options where appropriate.
Can Roundtower Help Specify a Rainwater System?
Yes.
If you are specifying or replacing gutters, downpipes, hopper heads or associated rainwater fittings, contact Roundtower Lime with photographs, dimensions and information about the building and roof arrangement.
We can help identify suitable cast iron or cast aluminium components and coordinate the products required for the complete rainwater system.
