TLDR
- Choose 5 or 6 in
- 2 × 3 downspout per 600 ft² roof min
- 3 × 4 downspout per 1,200 ft² roof min
- Downspout every 20 – 80 ft; upsize or add downspouts to suit
- Gutter guards
Overview
K-style style gutters are common in the US. The name comes from the shape of the gutter in cross-section and it's based on the Roman ogee shape, meant to replicate crown moulding profiles. Many installers can make 5" or 6" troughs and will install 2x3" downspouts or 3x4" downspouts. Often we treat the smaller sizes as more appropriate for residential use, and larger for commercial use but they can be mixed and matched.
Half-round profiles appear on historic or high-design projects but follow the same layout rules. Subcontractors roll-form continuous troughs on site, leaving the general contractor responsible for sizing, location decisions, and quality checks.
Prerequisites
- Fascia boards and drip edge installed and painted (if required) before gutter crew arrives.
- Measure roof-plan areas to confirm gutter/downspout sizing (see TLDR figures).
- Confirm discharge path—splash block, kick-out, or underground drain (verify daylight outlet).
- Decide with client on guard need and style (optional).
- Schedule gutter sub after roofing and any fascia paint touch-ups are complete.
Materials / Tools Needed
- 6 ft or longer level (quick pitch check)
- Hidden hangers (K-style) or wrap-around/bracket sets (half-round)
- Strip miters, end-caps, sealant rated for aluminum
- Stainless/self-piercing fasteners (interior—color not critical)
- Splash guards for inside corners; 10-ft splash blocks or elbows for discharge
- Optional guard panels & matching hardware
Process
- Layout & size. Using roof measurements, plan one 2 × 3 downspout per ≤ 600 ft² or one 3 × 4 per ≤ 1,200 ft² roof area.
- Mark downspout locations. The general contractor should mark up elevation drawings or photos of the project with troughs and downspouts. Coordinate with grade, walks, and aesthetics; space 20 – 80 ft apart and add extra or larger spouts where runs or valleys concentrate water.
- Color. Choose a color to coordinate with fascia, corner trim, or another detail on the home.
- Set high end & pitch trough. The installer will hang the trough targeting 1/4" of drop for ever 10 ft with hangers 24" O.C.
- Install downspouts. Strap every 6–8 ft and kick out away from the foundation or connect to drains.
- Add optional guards. Gutter guards can be added.
- Maintenance. Gutters should be cleaned regularly, at least once per year and up to 2 or 3 times depending on overhanging trees. Even homes with gutter guards need to have their gutters cleaned periodically.
Inspections
No separate inspection in many jurisdictions. In Michigan the GC must meet 2015 MRC R903.4 requirement for “controlled roof drainage.”
Client Interaction / Communication Notes
- Obtain approval on gutter size (5 in vs 6 in), downspout placement, color, and guard option before ordering.
- Explain routine cleaning: twice-yearly scooping or flush if un-guarded; debris sweep on guard tops each fall.
Common Issues & How to Avoid Them
- Size mismatch. Often the roll forming machine is installed in the back of a box truck or trailer. The installer will push you to install all troughs the same size so they don't have to mobilize two separate install crews for one project, or they will charge more to install a mix. They also need to know what size downspout to send because those are usually pre-made and not made on site.
- Overflow at inside corners. Install splash guard or add a downspout near the valley.
- Sagging trough. Increase hanger frequency to 18 in o.c. under heavy snow load.
- Ice-dam pull-off. Fasten hangers through fascia into rafter tails.
- Debris clogging. Specify appropriate guard or schedule regular cleaning.
Half-Round Gutter Considerations
- Commonly specified in galvanized steel, copper, or painted aluminum
- Half round are more expensive than K-style.
- Use fascia-mount or roof-strap brackets ≤ 24 in o.c.
- Same ¼ in per 10 ft pitch; 3 × 4 downspouts recommended for capacity.
