The gutter is the cheapest part of the roof and the part most often sized by eye. Illustrative photo.
Short answer: a new gutter supplied and installed runs roughly ₱450–₱700 per metre in uPVC and ₱550–₱900 per metre in pre-painted GI, with downspouts on top at about ₱350–₱650 per metre of height (AEDO 2026 estimates). A typical bungalow with two 12 m eaves lands somewhere around ₱15,000–₱30,000. The price matters less than the size, though. The Revised National Plumbing Code already tells you how much roof one downspout can drain (Table 11-1) and how big the gutter has to be at a given slope (Table 11-3). Most overflowing gutters we see were never checked against either.
The calculator below takes your roof's plan size, the rainfall you design for and the downspouts you want, then gives the code gutter size, the minimum downspout count, the gutter length and a cost band.
Sizes come from NPC Table 11-1 (downspouts) and Tables 11-3a/11-3b (semicircular gutters). Peso figures are AEDO 2026 estimates, anchored on retailer prices checked 18 Sep 2026.
Chapter 11 of the Revised National Plumbing Code of the Philippines covers storm drainage, and its tables work the same way for a bungalow as for a warehouse. Every table is read off the horizontal projected roof area, the roof as seen from above, and a rainfall intensity in mm per hour. Roof pitch doesn't enter into it. A steep roof and a flat one with the same footprint catch the same rain.
| NPC table | What it sizes | Example reading |
|---|---|---|
| Table 11-1 | Roof drains and downspouts (leaders), 51–178 mm, at 25.4 to 305 mm/hr | At 102 mm/hr a 76 mm downspout drains up to 204.4 m² |
| Table 11-2a/b/c | Horizontal rainwater piping at 10.4, 20.9 and 41.7 mm/m fall (§1104.3) | At 102 mm/hr and 10.4 mm/m, a 101.6 mm pipe takes 174.7 m² |
| Table 11-3a/b/c/d | Semicircular-bottom gutters, 76–254 mm, at 5.2, 10.4, 20.9 and 41.7 mm/m fall | At 102 mm/hr and 5.2 mm/m, a 127 mm gutter takes 58.1 m² |
Here is the part of Table 11-1 a homeowner actually uses, roof area in square metres that one downspout can drain:
| Rainfall (mm/hr) | 51 mm | 76 mm | 102 mm | 127 mm |
|---|---|---|---|---|
| 76 | 89.2 | 272.2 | 569.5 | 1,071.1 |
| 102 | 66.9 | 204.4 | 427.3 | 803.6 |
| 127 | 53.4 | 163.5 | 341.8 | 642.9 |
| 152.4 | 44.6 | 136.6 | 285.2 | 535.6 |
| 178 | 38.1 | 117.1 | 244.3 | 459.4 |
| 203 | 33.4 | 102.2 | 213.7 | 401.8 |
And Table 11-3a, gutters laid at 5.2 mm of fall per metre, the flattest slope in the table:
| Gutter (mm) | 76 mm/hr | 102 mm/hr | 127 mm/hr | 152 mm/hr |
|---|---|---|---|---|
| 102 (4") | 44.6 | 33.4 | 26.8 | 22.3 |
| 127 (5") | 77.5 | 58.1 | 46.5 | 38.7 |
| 152 (6") | 119.1 | 89.2 | 71.4 | 59.5 |
| 178 (7") | 170.9 | 128.2 | 102.2 | 85.3 |
| 203 (8") | 246.7 | 184.9 | 147.7 | 123.1 |
Compare the two tables and the lesson is obvious. The downspout is rarely the bottleneck. The gutter is. A 76 mm downspout at 127 mm/hr handles 163.5 m², but a 127 mm gutter at the same rain only carries 46.5 m² to it. You fix that with more outlets, a bigger gutter, or more fall, and more outlets is usually cheapest.
The code gives exactly one figure. A note under Table 11-1 says that for Manila and environs, a rainfall intensity of 102 mm per hour is used. It says nothing about Dumaguete, Bacolod, Davao or anywhere else. For those, the proper source is PAGASA's rainfall intensity-duration-frequency (RIDF) analysis for the nearest station. PAGASA releases it per station on request, through its data request channel and the eFOI portal, and it isn't something we can look up for you on a public page.
Without station data, the calculator defaults to the 127 mm/hr row, one step above the code's Manila figure. That's our engineering judgement, not a code value, and we label it that way. If you have RIDF data, enter it. Anything above 152.4 mm/hr goes beyond the gutter table's last column; the calculator then scales the roof area by the intensity ratio, which is how the table itself behaves (every column is roughly the same area-times-intensity product).
The common hardware-store downpipe is rectangular, sold as 76.2 × 50.8 mm. A footnote to Table 11-1 says round, square or rectangular rainwater pipe counts as equivalent when it encloses an inscribed circle equal to the leader diameter. The biggest circle that fits in a 76.2 × 50.8 mm section is 50.8 mm across. So for sizing, that "3-inch" downpipe is a 51 mm leader: 53.4 m² at 127 mm/hr, not 163.5 m². On a typical bungalow that's the difference between two downspouts and four.
Take a gable bungalow, 12 m along the eave and 9 m eave to eave including overhangs: 108 m² of plan area, gutters on both long sides, 127 mm/hr design rain. These are the calculator's defaults, so you can check each step.
Two eaves of 12 m is 24 m of gutter. At ₱550–₱900 per metre in pre-painted GI plus two 3 m downspouts, that's about ₱15,000 to ₱25,000 before any fascia repair.
Two retail listings anchor the material side, both checked on 18 September 2026: Wilcon Depot lists a P.Tech K-style uPVC gutter (2.45 m, 203 mm) at ₱496 per piece, about ₱202 per metre, and the matching 76.2 × 50.8 mm uPVC downpipe (2.45 m) at ₱464 per piece. Metalink lists a pre-painted box gutter, 24" × 8 ft, 0.40 to 0.60 mm, at ₱744.13 per piece, about ₱305 per metre of material. Installed rates below add brackets, outlets, end caps, sealant, fasteners, scaffolding and labour, and they're AEDO estimates:
| Gutter type | Installed, ₱ per m (AEDO est.) | Good for | Watch out for |
|---|---|---|---|
| uPVC (K-style) | 450–700 | Houses, low cost, no rust | Joints and end caps rely on solvent or rubber seals; sun-aging; brackets must be close enough to stop sag |
| Pre-painted GI box gutter | 550–900 | Matches long-span roofs; can be formed to a larger girth | Rust starts at cut edges, rivets and screw holes; needs sealed laps |
| Stainless steel | 1,500–3,000 | Coastal sites, commercial, long service life | Fabricator-made; get a quote per job, prices vary widely |
| Cast concrete gutter | 1,800–3,500 | Built with the roof beam or slab edge | Leaks through cold joints and cracks unless waterproofed; hard to resize later |
| Downspouts | 350–650 per m of height | — | Count by the inscribed circle, not the label |
Labour sits inside those rates. For a sense check, AEDO's labour rates guide puts skilled trades at roughly ₱650–₱1,200 a day and helpers at ₱500–₱700. Replacement adds removal and disposal of the old gutter, which the calculator prices at ₱80–₱150 per metre (AEDO estimate). These bands sit inside the ₱450–₱900 per metre gutter-and-downspout share used in our rainwater harvesting guide, and they're what the "flashing, ridge, gutters" line in our roofing cost guide is paying for.
Overflow that runs back behind the gutter gets into the fascia and eaves and shows up inside as a ceiling stain nowhere near the gutter. Our roof leak checker helps tell a gutter overflow from a flashing or sheet leak. Downspouts should discharge to a storm drain, a catch basin or a rainwater tank, not onto the foundation line, and the pipe that carries it away underground is sized from NPC Table 11-2, next door to the sanitary drain sizing in Chapter 7.
AEDO's role on a gutter or storm drainage job. Nationwide, AEDO designs the storm drainage as part of a plumbing and roof design: gutter and downspout sizes checked against NPC Chapter 11, downspout layout, and the underground run to the drain or tank. In Negros Oriental, AEDO also supplies and installs it, including replacing a failed system.
All gutter and downspout capacities, the 102 mm/hr Manila note and the inscribed-circle rule are read from the scanned pages of the Revised National Plumbing Code of the Philippines, Chapter 11 (Tables 11-1, 11-2a to 11-2c, 11-3a to 11-3d and their footnotes, and §1104.3). Material prices are retailer listings checked on 18 September 2026. Installed rates, the removal allowance, the 127 mm/hr default and the 600 mm bracket spacing are AEDO estimates or practice, labelled as such. One printed value in Table 11-3c (254 mm gutter at 51 mm/hr, shown as 133.8 m²) is plainly a misprint, since the 203 mm gutter above it reads 739.5 m²; the calculator doesn't use that table.
How much does a roof gutter cost per metre in the Philippines?
On AEDO's 2026 estimates, supplied and installed: about ₱450–₱700 per metre for uPVC, ₱550–₱900 for pre-painted GI box gutter, ₱1,500–₱3,000 for stainless, and ₱1,800–₱3,500 for a cast concrete gutter with waterproofing. Downspouts add roughly ₱350–₱650 per metre of height. For reference, Wilcon Depot listed a uPVC K-style gutter at ₱496 per 2.45 m piece and Metalink a pre-painted box gutter at ₱744.13 per 8 ft piece when we checked on 18 September 2026, material only.
What size downspout do I need?
NPC Table 11-1 gives the roof plan area each leader size can drain. At 102 mm/hr, the value the table's note uses for Manila and environs, a 51 mm downspout drains up to 66.9 m², a 76 mm downspout 204.4 m² and a 102 mm downspout 427.3 m². At 127 mm/hr those fall to 53.4, 163.5 and 341.8 m². Divide your roof's plan area by the capacity of the size you want for the minimum count.
Does a rectangular 3 × 2 inch downpipe count as a 3 inch downspout?
No. The Table 11-1 footnote treats round, square and rectangular pipe as equivalent when it encloses an inscribed circle equal to the leader diameter. The largest circle inside a 76.2 × 50.8 mm section is 50.8 mm, so it sizes as a 51 mm leader.
How much slope should a gutter have?
NPC Table 11-3 gives capacities at 5.2, 10.4, 20.9 and 41.7 mm of fall per metre. Flatter means less capacity: a 127 mm semicircular gutter at 102 mm/hr drains 58.1 m² at 5.2 mm/m and 81.8 m² at 10.4 mm/m. Pick the slope, then read the size from the matching table.
Why does my gutter leak or overflow?
Usually aged sealant at joints and end caps, rust at cut edges and fastener holes in GI, a clogged outlet, sag between brackets, or a gutter and downspout that are too small for the roof they serve. The last one is a design problem that no sealant fixes, so check it against NPC Tables 11-1 and 11-3 before re-installing the same size.
Plumbing code provisions, PAGASA data access, retailer prices and AEDO references used in this guide.
Installed per-metre rates, the downspout rate, the removal allowance, the 127 mm/hr calculator default and the 600 mm bracket spacing are AEDO's own estimates and practice. Stainless and concrete gutter rates have no public retail benchmark; get a fabricator or contractor quote for your job. Retail prices change; check the listing before you buy.
Size it once, from the code, and stop paying for the same gutter twice.
