- Setting out the falls
- Outlet positions
- Bracket spacing
- Joints and the eaves detail
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Fitting Trimline Steel Guttering
Guttering looks like the simple part of a roof and is the part most often got wrong. Almost every overflowing gutter we are asked about comes back to one of three things: not enough outlets, no fall, or the roof sheets discharging behind the gutter instead of into it.
Work through the setting out on the ground before anything is fixed to the building. It is far quicker than adjusting brackets at height.
1. Fix the outlet positions first
Outlets, not gutter size, do most of the work. A gutter fills from the far end towards the outlet, so a long run with a single outlet carries the whole volume at its downstream end.
Set the outlets out first and let the brackets follow. Adding a second outlet is usually more effective than going up a gutter size.
2. Set the falls
Run a line from the high point to each outlet and set the brackets to it. A consistent fall towards the outlet is what stops water standing.
A level gutter holds water, which collects debris, accelerates corrosion and freezes. The fall is worth setting out properly.
3. Brackets
Fix brackets at the spacing specified for the system and keep them to the line you have set. Add a bracket close to each side of a joint and each side of an outlet, where the load and the movement are concentrated.
Check the line again once all the brackets are on and before any gutter goes in. A dip between two brackets will hold water for the life of the building.
4. Joints
Make joints up cleanly, with the surfaces dry and free of swarf and dust. A joint made onto a dirty surface will seal on the day and weep within a season.
Allow for thermal movement. A long steel gutter run in full sun moves, and a run pinned rigidly at both ends has nowhere to go.
5. The eaves detail
This is the one to get right. The roof sheets must discharge into the gutter, not behind it. Check the sheet overhang along the whole run, not just at one end, because a sheet that overhangs correctly at the gable can be short in the middle.
The eaves detail should also stop wind-driven rain tracking back under the sheet. Our flashings and trims are made to suit the profiles we supply.
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6. Downpipes
Take the downpipe to a drain or a soakaway, not to the base of the wall. Water discharging against a building is how ground floors get damp, and it is entirely avoidable at this stage.
Fix the pipe back to the wall at the specified centres so it does not move in the wind and work the joints loose.
7. Before you finish
Pour water in at the far end of each run and watch where it goes. It should reach the outlet without ponding anywhere, and nothing should weep at a joint. Five minutes with a bucket now saves a return visit in the first heavy rain.
Finally, think about how the gutter will be cleared in future. A gutter that cannot be reached will not be maintained, and that is usually what kills it. Our article on choosing the right steel guttering system covers the design side in more detail.
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