Has my builder mucked up plastering our bedroom

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Hi,
We had our bedroom replastered as the plasterwork was terrible. The room had this weird plasticky paint on it and once that was removed and the plaster redone, the (internal) plasterwork on the external wall has damp patches and has refused to dry.

Our builder has said it is due to an ornamental lintel on the outside of the house catching rain and causing it to penetrate and suggests removing the lintel, redoing the rendering and then replastering the internal side of the wall with a cost around £3,000

However, just got another quote and they have said our builder co##ed up and while it is fine to use gypsum plaster on internal walls, the builder should have used a different plaster on the internal side of the external wall: using sand and cement to create a waterproof membrane. Cost £500.

This new builder is saying that our builder should have known this, should have noticed it was wet when he was replastering (at which point they could have asked us what we wanted doing) and that they should rectify it for free.

As I know very little about plaster, I am just wondering if this sounds plausible and whether you really need a different plaster for the internal side of an external wall?

Thanks in advance
 
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Hi,
We had our bedroom replastered as the plasterwork was terrible. The room had this weird plasticky paint on it and once that was removed and the plaster redone, the (internal) plasterwork on the external wall has damp patches and has refused to dry.

Our builder has said it is due to an ornamental lintel on the outside of the house catching rain and causing it to penetrate and suggests removing the lintel, redoing the rendering and then replastering the internal side of the wall with a cost around £3,000

However, just got another quote and they have said our builder co##ed up and while it is fine to use gypsum plaster on internal walls, the builder should have used a different plaster on the internal side of the external wall: using sand and cement to create a waterproof membrane. Cost £500.

This new builder is saying that our builder should have known this, should have noticed it was wet when he was replastering (at which point they could have asked us what we wanted doing) and that they should rectify it for free.

As I know very little about plaster, I am just wondering if this sounds plausible and whether you really need a different plaster for the internal side of an external wall?

Thanks in advance

Never heard of that and can't see the logic. ANY internal wall shouldn't be facing any kind of dampness. So, the first builder might be right. Second builder sounds worse as it's not solving the problem is it? there shouldn't be any damp coming through at all

I'm new to plastering etc so I'm sure a Pro will be along to help but this sounds like common sense to me..
 
It is probably around 100 years old and is just a two up, two down (Gerorgian maybe) terraced house and due to the age I can't imagine it has a cavity wall.
 
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It is probably around 100 years old and is just a two up, two down (Gerorgian maybe) terraced house and due to the age I can't imagine it has a cavity wall.

I've not had to deal with older properties, so this is based on what has come up on this forum before.
Older properties with no cavity were generally done with lime plaster. Lime plaster allows the wall to breathe i.e. allow some moisture movement.
Modern finishes (e.g. gypsum plaster) don't do this and in fact tend to draw moisture through from a damp wall. As you're seeing.

In some ways both builders were correct to some extent.
Builder #1 was trying to reduce the moisture in the external wall with the suggested change outside. This would at least give a gypsum internal finish more chance.
Builder #2 recognises that cement render with a waterproofer in it can reduce moisture transfer. It is usual to fix the source of any damp first, if there is a particular problem e.g. Leaky gutter. It may do the trick, or give you more problem in the long run.
There are also other options too if you don't mind losing a bit of space on the wall.

I would do some reading up and perhaps post some pictures here.
There are some knowledgable pros who can probably offer help too, some pics are usually easier to respond to.
 
Thanks for that, will take some pictures tonight and post them up (not sure why I didn't think to do that in the first place!)
 
What sort of roof have you got?, Can you give us a photo of both sides of the window and an overall picture of the top of that area where the window is situated. It looks like the problem is around that area either from the roof or the wall . As for what plaster/render you have to put internally is not the issue at the moment ,there is damp penertrating the wall and you have got to find out where it is comin' from...
 
Have you got a flat roof and a parapet? And can you get a photo of the roof structure from further back? You can see the "damp" line in the picture of the left hand side of the window..
 
Yes as roy c has said I would investigate the roof. I would consider re-posting this in the building section as a 'damp problem', then if the chief suspect looks like the roof then head to the roofing section! :p
 

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