Downspout Installation & Roof Drainage

A gutter only collects water – the downspouts decide where it goes. Too few downspouts, or downspouts that dump water right next to the house, are among the most common causes of overflowing gutters, eroded flower beds and wet basements and crawl spaces.

Downspout basics

• A common rule of thumb is one downspout for every 30 to 40 feet of gutter, more on steep roofs and in heavy-rain regions
• 2x3-inch downspouts are standard on 5-inch gutters; 3x4-inch downspouts carry much more water
• Extensions or splash blocks should move water several feet away from the foundation
• Underground drain lines can carry water to a safe discharge point in the yard

Typical costs

Item	Typical range*
Downspout, installed (per linear foot)	$5 – $16
Downspout, installed (each)	$50 – $240
Upgrade to oversized 6-inch gutter (per foot)	+$3 – $5

*General US ranges compiled from 2026 cost guides (Angi, HomeGuide, This Old House), for orientation only. Local installers set their own prices.

Common drainage mistakes

• Downspouts that end right at the foundation wall
• Upper-roof downspouts dumping onto a lower roof without a diverter
• Long gutter runs with a single downspout at one end
• Buried drain pipes that are crushed or clogged and back up into the gutter

When you get connected, mention any water problems around your home. The installer can plan downspout locations and extensions as part of your new gutter system.