Guttering, downpipes & stormwater

Every gutter system needs somewhere for water to go when the storm exceeds what it was designed for, and that place must be outside the building. Eaves gutters are generally designed to spill over the front edge, which is why the front of a gutter should sit lower than the back. Get that backwards and the overflow direction is into the fascia, the eaves and the ceiling.

Box gutters are the serious version of this. They sit inside the roof line, usually between two roof planes or behind a parapet, so a blockage or an undersized outlet has nowhere to spill except into the building. They require sumps or rainheads, correctly sized outlets, a minimum fall along their length, and a dedicated overflow that discharges visibly outside. Box gutter failures are among the most expensive water damage events a building can have, and they are nearly always a design or maintenance failure rather than bad luck.

Quad is the standard domestic gutter and does most of suburban Melbourne. High-front quad carries more and is a straightforward upgrade where capacity is marginal. Half-round suits period homes and sheds water well. Square-line and fascia gutters suit contemporary builds. Slotted variants let water escape the back of the gutter deliberately in some designs.

Fascia cover is worth mentioning because it is often where the rot is. On older homes the timber fascia behind the gutter has frequently been wet for years. Capping over rotten timber hides it rather than fixing it, and the gutter brackets end up fixed to something that will not hold them.

A gutter is only as good as the downpipes taking water out of it, and the connection into the stormwater system below. Downpipes that discharge onto the ground beside a footing, or into a stormwater line that was blocked with roots years ago, will back up the whole system in a storm regardless of how good the guttering is.

Where a system keeps surcharging, the answer is to look underground rather than to keep replacing what is visible. A camera down the stormwater line usually finds the cracked or root-filled section that has been causing it.

Under overhanging trees, gutter guard earns its money. It stops the repeated cleaning cycle and, more importantly, stops wet leaf litter sitting against the steel, which is what kills guttering early on the shaded side of a house.

On an open block with nothing overhanging, it is usually money better spent elsewhere. Guard is also not maintenance-free; it moves the debris from inside the gutter to on top of it, and on a valley or a low-pitch roof it still needs looking at.