DIY Doctor UK DIY Forums

I have a new build house (2 years old) a damp patch has been present for about 6-8 months (see pictures)

there are no obvious holes in the brick work, the window ledge seems sealed well enough.

The builders Wheeldon Brothers say our two year warranty is up so they wont do anything and NHBC say unless it is coming in internally they wont do anything.

Has anyone seen this before? If I leave it will it rot/corrode the cement and brick work?

Any advice is welcome thank you.

that's unusual, I would say a pipe was leaking, causing that amount of damp.
You can hire a borescope from your local hire shop, drill a hole in the cavity and check for the cause

Hi
If not pipe it might be salt contamination. By mistake one of the sand bag was with unwashed sand?
Hard to say