Could lumpy patches on rendered external walls indicate damp issues?

[Nonstandardsolution]

We’ve been to see a house today and on a few of the external walls there are lumpy areas - is the damp? House is rendered over brick and about 70 years old - ex council house.

Is that internal or external?

Yes, that would be my first guess from your picture.

This is an internal wall between the bathroom and hallway. (Back door is pictured)

This is a zoomed out pic

Either damp or a previous water ingression (a leak from somewhere)

Quite likely a plumbing leak in the bathroom then. Have a look on the other side of the wall. You might have to rip off tiles to get at the origin of the water

That's not what you said in your thread title. Show us the other ones please.

You can buy a damp meter from BandQ and check if you have a second viewing
The slight yellowing suggests damp

It might be but it might be an old leak. You may have to chip it off to see. I had this with an external wall and it wasn't too bad under it all.

Sorry, yes this is an internal wall close to the back door. I’m wondering if moisture is tracking in form the outside

See some further pictures. The one between the hall (back door) has a radiator on the wall in the bathroom on the other side. The other walls in the kitchen are external walls. The EA says the marks on the wall circled are ‘grease’ marks but I can’t see how as it’s not near the cooker. What appliance would leave greasy marks up the wall? A chip fryer maybe?

Is there a down pipe on the other side of that wall next to the window?
That looks like repair work after the plaster has blown due to moisture
Either that or there used to be a wall cupboard there and they’ve done a bad fix

Again if use a damp meter on that to check

Damp meters are only accurate if you use them on wood so take any other readings with a pinch of salt.

We use them as Architects all the time
They are not just for wood and readings are very representative of the damp conditions of walls

@BrownTroutBluesAgain

I may have misunderstood but i thought most damp meters just measure electrical conductance? I think conductance should go up when there is more damp and down when there is less damp but wouldnt be able to distinguish between damp inside the wall and condensation. This sort of device would also struggle if there were things like high salt levels in the plaster and wouldnt be able to mesure the dampness of the wall at all if it were painted in some sort of damp blocking paint.
Are you using different meters or have i totally misunderstood how they work?

I can spot attempts at hiding damp with sealants a mile off 🤣

Using prongs to test the walls it’s easy to bypass any disrupters. Obviously if owners have gone hell for leather with multiple layers you won’t get accurate readings ( but the wall will become progressively flakey or/ and coloured if the source problem hasn't been fixed )

Yes salts in plaster can disrupt readings making them artificially high but the presence of salts highlights an historical problem with damp.
So if you get a high reading questions need to be asked

So they are representative if you have an understanding of the things which could throw them off? But basically all high readings should be investigated.

Looks like a damp problem to me. Sometimes houses have cavity wall insulation that has got wet trapping moisture inside the walls, or wicking moisture from outside to inside. It could be the render itself not allowing the property to breathe. At the least I think you would need specialist advice on the cause of the issues and the fix.

Edit to say that the place looks reasonably recently decorated so you wouldn't expect these problem areas if there were no issues. Ignore the estate agent - they will say anything to get a sale.

Looks like attempts to fix / hide damp on the walls to me: if it's a traditionally built house that used to have lime plaster and they've gypsumed over it, and they had a stone floor that they've concreted or tiled over: recipe for damp. When modern materials go over traditional ones it's a moisture magnet.