Hello all, Any advice on what this could be? It’s 1930s house and on outside walls. Only thoughts are a damp or grease patch.
The roof and gutting are in good shape, with minor repairs done a couple weeks back. First thought was water coming in to the cavity. There are no cracks on the outside render but some parts still appear wet (according to moisture tester). Weather has been good, some parts may have tried out but difficult to say.
Tried zinsser bin primer but still coming through!
Hi lc1986, Most likely to be cracks in the render close to opposite where the damp is appearing. Once a rendered wall gets internally damp it can take a long time to dry out. Check the falls on the gutter and the condition of the underslaters felt above the damp area. Regards S
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