Hide Downpipes (Decorative Metal Pipe Chutes)

A removable metal chase can screen an exterior rainwater downpipe without hiding leaks or blocking drainage. First, trace the full pipe and locate every joint, cleanout, offset, and outlet. Then size the enclosure around its largest fitting, keep service panels removable, and direct water away from the foundation. Check local code and manufacturer instructions before building.

A bare downpipe can interrupt an otherwise finished wall, but covering it too tightly can turn a small leak into hidden water damage. A good decorative chase hides the pipe from view while leaving the drainage route visible when you need to inspect or repair it.

I plan these enclosures around the pipe, not around a standard box size. Pipes often have elbows, straps, cleanouts, or wall connections that need more room than the straight section. The details below help you plan a durable metal cover without treating a design allowance as a code rule.

Plan the Chase Around the Existing Downpipe

A chase is a separate enclosure around a downpipe; it should not carry the pipe’s weight or change its route. Before choosing metal or measuring panels, trace the water path from the roof inlet to the final discharge. That survey reveals where the enclosure needs extra room and access.

Start at the top and follow the pipe down. Mark each elbow, joint, strap, cleanout, wall penetration, outlet, and any overflow or secondary drain. Note which parts connect to siding, trim, or a drainage fitting, and check where the water goes after it leaves the pipe.

Measure the widest point, including fittings and straps, rather than only the pipe diameter. As a design allowance, leave at least 1 inch (25 mm) of clear space around the pipe where practical. Add room where joints, offsets, straps, or movement need it. This is not a code minimum; the actual clearance depends on the pipe layout and service needs.

Draw the chase as a simple plan and side view. Show the wall, pipe, fittings, access face, and outlet. This makes it easier to spot a panel that would cover a joint or leave too little room to remove a fitting.

• Confirm the pipe is sound and the outlet works before covering it.
• Check that the proposed chase will not hide another drain or overflow.
• Keep the outlet in its existing designed position unless a qualified professional approves a change.

Preserve Access, Clearances, and Discharge

Access means being able to inspect and reach the parts most likely to need attention, not just seeing a stretch of straight pipe. Plan removable panels at joints, cleanouts, and the outlet. Leave enough room to take those panels off without bending the pipe or damaging nearby siding.

Make the face that gives the best access removable. Depending on the layout, that may be a full front panel or several smaller panels with fasteners suited to outdoor use. As a design allowance, aim for about 2 inches (50 mm) of working space at the service side where the site permits. This is not a code minimum, and a tight site may require a different access plan.

Do not seal the chase into an inaccessible, watertight cavity. A metal cover can shed most rain, but water may still enter at an opening or a leaking connection. The design should let incidental moisture escape rather than trap it against the wall or pipe. Keep the pipe’s outlet, any required overflow, and secondary drainage unobstructed.

Most exterior rainwater downpipe chases do not have a general prescribed airflow rate, so there is no universal CFM target. Still, avoid a design that traps water or prevents inspection. The needed openings and clearances depend on the system and the enclosure details.

A simple access check helps before fabrication: can you remove the panel, see the joint, reach the cleanout if present, and inspect where water exits? If not, revise the panel layout before the metal is cut.

Frame, Weatherproof, and Finish the Metal Enclosure

The frame holds the decorative panels, while the downpipe remains independently supported. Anchor the chase to suitable structure, not to the pipe. Choose supports and fasteners based on the actual wall material, exposure to corrosion, and expected loads; use the manufacturer’s published capacity rather than guessing from fastener size.

Lay out the frame so it does not clamp, rub, or load the pipe. Keep the top and wall interfaces shaped to shed water away from the building. Provide a way for incidental moisture to drain or escape, and avoid creating a pocket where water or debris can collect.

Use materials and fasteners that are compatible with one another and suitable for the site’s exposure. Galvanized sheet metal is one possible choice. ASTM A653/A653M G90 means a total galvanized coating of 0.90 ounces per square foot (275 grams per square meter) across both sheet faces. G90 describes the coating, not the sheet’s thickness or structural strength.

For a clean appearance, align panel edges with nearby trim where practical, and use a finish intended for exterior exposure. The panels should come off without cutting sealant, pulling apart the wall’s weather barrier, or damaging the pipe. Avoid relying on a permanent bead of sealant as the only means of access.

Before finalizing the finish, check how the cover meets siding, masonry, or trim. A neat edge is useful, but it must not direct runoff behind the wall cladding. Follow the building-product instructions for any flashing or water-shedding detail at that interface.

Verify Drainage, Serviceability, and Code Compliance

A finished chase is only successful if water still follows its intended route and a person can inspect the important parts. Test the drainage before considering the work complete. Also confirm the rules that apply to the property, since adopted codes and local requirements can differ.

Under IRC Section R401.3, the general grading benchmark is a fall of 6 inches (152 mm) within the first 10 feet (3.05 m) away from the foundation, subject to the section’s exceptions. Confirm the locally adopted code edition and how the rule applies to your site. The chase itself must not redirect discharge toward the foundation or create a nuisance.

After installation, run water through the roof-drainage system and watch the pipe, joints, outlet, and nearby ground. Look for leaks, ponding, debris buildup, or water entering the chase. If a joint leaks, fix it before closing the access panel; hiding a leak can allow water to reach the wall or foundation before the damage is noticed.

Use this final check:

• Confirm water exits through the intended outlet.
• Inspect visible joints and connections while water is flowing.
• Check that the discharge does not undermine the foundation or create a nuisance.
• Remove and replace each service panel to confirm it can be accessed later.
• Check that the enclosure does not block an overflow or secondary drain.
• Recheck the work against local code and the drainage system manufacturer’s instructions.

Installation Scenarios: What Changes the Design?

These are planning examples based on common layout conditions, not reports of named projects. They show why a chase should be sized and opened around the actual pipe route. Use them to identify details to check at your home before ordering or fabricating panels.

Site condition	Design response	Check before closing
Straight pipe with few fittings	A narrow chase may work if it has the planned clearance and a removable face.	Confirm there is room to inspect the pipe and remove the panel.
Offset near a wall or corner	Widen the enclosure around the largest elbow or fitting.	Make sure the offset and its connection remain visible and reachable.
Cleanout or service joint behind the proposed face	Place a removable panel at that point, or revise the chase layout.	Confirm the opening exposes the full service area, not just the pipe beside it.
Outlet close to the ground	End the chase above or around the outlet without restricting discharge.	Run water and verify it leaves by the intended route.
Chase meets siding or trim	Detail the top and wall edge to shed water away from the building.	Check for water paths behind cladding and a way for incidental moisture to escape.

For example, a straight run may appear easy to cover until an elbow sits behind a narrow panel. In that situation, the widest fitting sets the enclosure size. A second common planning challenge is an outlet close to the ground: the cover must not reduce the opening or send water toward the foundation.

Common Questions About Decorative Downpipe Chases

These answers cover the choices homeowners most often face when planning a metal enclosure. Local code and product instructions still control where they apply. If the pipe serves a complex roof-drainage system, ask a qualified installer to confirm the route before concealing it.

How much space should I leave around the pipe?
As a design allowance, provide at least 1 inch (25 mm) of clear space where practical. Add room for fittings, straps, movement, and repair access. It is not a universal code minimum.

Can I attach the chase to the downpipe?
Do not use the pipe as the chase’s structural support. Anchor the enclosure to suitable structure and keep it from clamping or loading the pipe.

Does a metal chase need ventilation?
There is no general prescribed airflow rate for this type of chase. Avoid trapping water, and provide access and a path for incidental moisture to escape.

Should the access panel cover the entire face?
Not always. It must expose the joints, cleanouts, or other service points that need inspection and repair. A larger removable face can be useful when smaller openings would block access.

Can I cover the downpipe outlet?
Do not obstruct it. Keep the outlet and any required overflow or secondary drain open, and preserve the designed discharge route.

What does G90 galvanized steel mean?
G90 identifies a total zinc coating of 0.90 ounces per square foot (275 grams per square meter) across both sheet faces. It does not specify the sheet thickness.

How do I check that the chase still drains properly?
Run water through the roof-drainage system. Watch the joints and outlet, and check for leaks, ponding, or water entering the chase.

What grading rule applies near the foundation?
IRC Section R401.3 gives a general benchmark of 6 inches (152 mm) of fall in the first 10 feet (3.05 m), subject to exceptions. Confirm the locally adopted edition and its application to your site.

Final Planning Check

A well-designed metal chase hides the downpipe without concealing the parts that matter. Measure around the largest fitting, keep the service face removable, support the enclosure independently, and protect the wall and discharge path from unwanted water.

Before finishing, run water through the system and inspect the joints and outlet. If the chase blocks access or changes where water goes, revise it before treating the job as complete.

(This article was written by one of our staff writers, David Sinclair. Visit our Meet the Team page.)