Assuming the gutters have the correct slope the main reason for overflows is that the gutters are full of debris and need to be cleaned.
Water leaking between gutter and fascia.
Without looking at the roof it seems that the water is missing the guttering because perhaps the previous owners may have had new fascias overlaid onto the old.
2 the more common reason is where roof sheets are cut too short or they don t overhang far enough into the gutter.
Water leaking between gutter and fascia when there is rain the water is expected to roll down the roof and into the gutters.
But what happens when your roof s gutters become worn out or cracked or clogged.
Have rain water dripping out from between your facia and gutters.
This can be frustrating and also creates a dangerous situation on porch steps during freez.
This then pushes the guttering out from the roof line by 9 17mm.
The gutters then direct the water to a downspout allowing the water to run down until it reaches the ground.
If you re not closely attuned to the behavior of your home s water drainage system you may not notice this occurrence.
It s a common reason water gets between the gutter and fascia.
When water drips between the fascia and the gutters the problem could be a compromised drip edge but it s also possible the gutters are overflowing.
Drip strip is designed to fill the gap between the bottom of the drip edge and the top of the gutter to insure the water will flow into the gutter preventing any damage to your fascia or other parts of your home or landscaping.
Any rainwater or in sparodic areas then simply misses the gutter.
If the gutter fills with water from organics knitting together over your downspout water can spill behind the gutter.
1 your roof sheets have a hole in them or your screws or nails or equivalent are not watertight anymore or.
On some homes water tends to drip behind the gutters down the fascia and soffit and then either down the side of the house or straight to the ground.
Usually this is due to gutter fasteners rusting.