Should a felted roof be water tight ?

[Terry lambert]

Hi fellas

I wouldn't normally scrutinise someone's work this much but the builder doing my extension has made some howlers.

The roof had been felted and battened, I've been led to believe by some that this should be watertight as if a tile cracks or problem with the ridge the it is a second level of protection.

I've read elsewhere roofers saying no, that's not its purpose and if you get a cracked tile, then you replace the tile.

What's correct ?

With a bit of rain tonight it's coming into the extension ( not tiled yet) it's coming in around the Veluxs

Many thanks

 

[datarebal]

Tiles do the weathering.. Cracked tile then change it.. In this case Your guy needs to re visit the way he has weathered the underlay to the velux, Just mention it to him that it leaked.
Keep in mind not all breathable membranes are Waterproof.. some just water Resistant If you get heavy rain over a period of time then you can get drips. Depending on product used

 

[^woody^]

The tile underlay is (should be) water tight when the tiles are covering it and flashing fitted - ie will deal with any rain that gets past the tiles.

But without the tiles above, the underlay is prone to any driven rain, and penetration at its junction with walls or at edges (like around veluxes) where flashing would be otherwise be fitted.