Short answer: put a hidden gutter hanger every 18 to 24 inches along the run. Go tighter than that on long unsupported spans and anywhere that carries real snow load. Almost every sagging gutter we get asked about is spaced wider than 24 inches, or is hung on spikes that have worked loose.
Why 18 to 24 inches
A gutter full of water is heavier than people expect. A 5-inch K-style run carries roughly a gallon of water per foot when it is flowing full, and a gallon weighs about eight pounds. Add wet leaves, ice, or a ladder leaned in the wrong place, and the load between two hangers is what decides whether the run stays straight.
Spacing at 18 to 24 inches keeps the unsupported span short enough that the gutter lip cannot flex and start to oil-can between brackets. Once a run develops a low spot it holds standing water, and standing water makes the low spot worse. Spacing is the cheapest insurance against that, because hangers cost far less than re-hanging a run.
When to go tighter than 18 inches
- Snow country. Ice loads are the real test. If your area gets ice dams, work at 16 to 18 inches.
- Long straight runs. A 40-foot side with nothing but hangers holding it needs more of them than a short run broken up by corners.
- Above a door or walkway. Anywhere a failure would drop water on somebody, tighten it up.
- 6-inch gutters. A wider trough holds more water, so the load per foot is higher. Stay at the tight end of the range.
Where to add one regardless of spacing
Put a hanger within about 12 inches of each end of a run, on both sides of every seam, and near any inside or outside corner. Those are the points that move first. The regular spacing then fills in between them.
How to check spacing on a gutter that is already up
You do not need to get on the ladder to do the first check. Stand back and sight along the length of the run against the roof line. A correctly hung gutter reads as one straight line. If you can see a dip, the hangers on either side of it are either too far apart or not driven into anything solid.
Then get up and measure. Hook a tape on one hanger and read across to the next. If you are finding gaps of 30 or 36 inches, that is the problem, and adding hangers between the existing ones will usually pull the run back to line without taking anything down.
What the hanger is screwed into matters more than the spacing
This is the part that gets missed. Spacing only helps if each hanger is anchored in something that can carry load. The screw needs to pass through the back of the gutter, through the fascia board, and into the rafter end behind it. Fascia board on its own is a piece of trim. It will not hold a full gutter for long, no matter how many hangers you put in it.
If the fascia is soft or rotted, no hanger and no spacing will fix it. Replace the board first. A hanger is only as good as what it is screwed into.
Working out how many you need
Divide your total run in feet by 1.5 for 18-inch spacing, or by 2 for 24-inch spacing, then add a few spare for the corners and ends. A 120-foot house at 18 inches comes out around 80 hangers, so a 100 pack covers it with sensible margin.
We wrote that out properly, with worked examples, in how many gutter hangers do I need. If you already know your number, shop by pack size lists every pack from 10 up to 500.
Getting them in
BULDER hidden hangers ship with the screw already fitted in the bracket, so there is no loose hardware to line up one-handed at the top of a ladder. One 1/4-inch nut driver does the whole job. The full sequence is on our installation guide.
They fit K-style profiles in aluminum, and vinyl and plastic too. Pick the size that matches your gutter: 5 inch or 6 inch. If you are not certain which you have, here is how to tell them apart.
Still not sure about a particular run? Call us on (732) 730-7334. We answer the phone, and we would rather talk it through before you are up the ladder than after.
Common questions
Is 18 to 24 inches a rule or a recommendation?
It is our recommendation. The wider industry range is commonly published as 24 to 32 inches, with 36 inches as a maximum. We recommend tighter because more support points mean more margin before anything sags, and hangers are the cheapest part of the job.
Does spacing change for vinyl or plastic gutters?
No. Spacing is decided by the load the run carries, not by what the trough is made of. Our hangers are made for aluminum K-style gutters and fit vinyl and plastic K-style too. On vinyl, support the section while you drive the screw so the lip does not deform.
Do gutter guards change the spacing?
Work at the tight end of the range. Guards add weight of their own and hold snow on top of the run instead of letting it drop through, so the load between hangers goes up.
Can I just add hangers between the existing ones?
Usually, yes. If the trough itself is straight and the fascia is sound, adding hangers between the existing ones will pull most runs back to line without taking anything down.