Damaged caused by blocked gutters includes
Water that over flows from the gutters can saturate the brickwork, bricks can absorb moisture and become water logged this will make the bricks softer. During periods of freezing weather the moisture within the brickwork can expand a blow the face of the bricks off, this will make the brickwork less weather proof.
Moisture can also be the cause of the mortar between the joints in the brickwork to become loose, holes can start to appear in the pointing, which can cause structural problems.
If the brickwork is constantly damp due to moisture caused by blocked gutters, moss and algae can grow on the brickwork which can look very unsightly.
When a guttering system cannot cope with the volume of water it has to disperse it will over flow. This overflowing water is either absorbed by brickwork or it can quite often find its way behind the brickwork. For building that where built before the introduction of the cavity wall, brickwork can become so water logged that the water can be absorbed right through the wall which can make the plasterwork on the inside of the property damp.
The plaster on the walls inside a property is just as porous as the brickwork it is stuck onto and therefore when it becomes damp the water can be absorbed right though it. Damp plasterwork becomes weak and can become loose on the walls.
Because the emulsion paints that are used to pant over plaster are water based they do not respond well to being damp, the damp plaster can cause the paint to flake off exposing the plaster that it was painted onto.
When blockages in the guttering system prevent the water from flowing more that 5 meters away from a building, pools of water can be absorbed by the ground around the foundations of the building. This moisture can find weak points in the foundations and can be absorbed.
Excess water can also flow below the foundations of a building and undermine them. Damage to the foundations of a building is an extremely serious problem and can be extremely costly to re-pair. If the foundations on a property start to fail large cracks can start to appear on the brickwork, this is one of the first sighs of subsidence. It could cause the building to sink and become misshaped. Allowing water to sit around the foundations of a property should be avoided when ever possible.
When the rainwater is not diverted far enough away from the property it can pool around the property, this water is then generally absorbed by the ground and can pool around the brickwork of a cellar or basement. The water can then get absorbed by the brickwork and if the volumes of water are large enough it can create server damp or even flooding in the basement or cellar.
When the rain water is not directed properly into the drainage system it can leaves the down pipes and end up washing over the paving next to the building. The excess moisture over the paved area can promote moss and algae growth that can become very slippery and dangerous when wet.