We have a house with two pathways either side. The pathways are 14m x 0.85m. Some of the slabs are uneven and angled towards the house and after heavy rain or excess waterflow from loft tank, the water then sits in a pool by the house brickwork. Then eventually goes down. Can this cause damage to the foundation? Also there are small gravel gutter areas between paving and house, are these pointless and should I replace the mud in there with gravel? If so, what size?
A large amount of water, like a burst pipe, an overflow, etc could wash away soil etc from foundations. It depends on the situation. But rainwater would not usually cause a problem, unless it's a drainage point from a large catchment area. Is it a gutter, or a French drain. A gutter would take water away to a drainage point. A French drain would allow water to drain directly to the soil, percolating slowly through the gravel. Either way, it's not working properly if it's full of mud. If it's a gutter, it doesn't need anything in there. if it's a French drain, it ought to have a permeable layer stopping the gravel and mud mixing, and the gravel could be pea-gravel or chippings (about 10mm to 40mm) as used in concrete, but not ballast. Pea-gravel is more decorative.
I believe you are confusing the original use of the term “ French drain “ with its current UK usage which incorporates slotted or perforated drainage pipes in the trench, and only pea gravel not chippings to prevent the geotextile membrane being punctured. Just saying
I believe its just a gutter. Weirdly half of it is cemented and the other half is pea gravel and mud underneath. My main concern is whether my neighbour's overflow issue which resulted in gallons of water in our pathway would do anything to our house foundation?