Painting throughout - gypsum plaster & wallpaper

[leyasg]

After the first leak, which (hopefully has now been resolved - thanks Cubist & all who helped!), we are back on track to refurbish the house. The next (supposedly first) task is re-painting internally throughout. There is a lot going on, with damp patches in 3/4 places (not related to the previous leak we had), wall paper and what looks like Gypsum plaster in parts of the house when I thought the whole house had lime render. Images attached.

Questions:

1. Is it definitely Gypsum? Photo attached for one part. Have done the vinegar test and it didn't fizz but wondering if it could be something else? Also am wondering whether I should test it out in every room throughout the house before we paint? This part of the house is more modern (built in 1980s) so it could be an isolated section.
2. Should we just paint over the gypsum with traditional paints? I am guessing there is little point using mineral/clay paints on Gypsum.
3. Is it worth stripping all the gypsum plaster and re-doing it with lime plaster? For the modern portion of the house, there would be no requirement for the building to breathe?
4. Would there have been a reason why the previous owners used plain white wallpaper rather than painting? Just seems absurd to me, unless there are benefits to wall paper I am not aware of?
5. Is there anything I need to be aware of/any specific area I need to be careful when removing wall paper from lime plaster (if there is lime plaster in other parts of the house below the wallpaper)? Any tips/tricks appreciated.

As for the specific paints on where it is lime render, Earthborn has always been positively advertised on the forum. What are the practical advantages and disadvantages of each? We just want plain white ish walls.

As always, help appreciated.

 

[Cubist]

Your absolute top priority needs to be the investigation and identification of the source(s) of the damp patches. Decorating the affected walls without resolving the issue effectively would be pointless and wasteful. Where in the house are you seeing these damp patches? Are they on the ground floor or upper floors? Are they visible on walls that have an outdoor elevation? Do they appear high on the walls or low down near skirtings?

Regarding your queries above;

1. Is it definitely Gypsum? Photo attached for one part. Have done the vinegar test and it didn't fizz but wondering if it could be something else? Also am wondering whether I should test it out in every room throughout the house before we paint? This part of the house is more modern (built in 1980s) so it could be an isolated section.

The colour suggests gypsum but it really does not matter at this stage. The key question is - is it sound and largely undamaged? If it is in good condition then leave it alone. Breathability is important but gypsum plasters are not entirely impermeable and are therefore merely less efficient than lime based plasters. The only tests you need to be concerned with in each of the rooms is for the presence of obvious damp and/or damaged/failed plaster.

2. Should we just paint over the gypsum with traditional paints? I am guessing there is little point using mineral/clay paints on Gypsum.

No. The previous owners did you a favour by papering the walls with a lining paper. This is often used to hide imperfections in plaster AND to avoid patchy finishes when the paint is applied directly to the plaster. Do yourself a favour, remove any damaged, torn or loose or peeling paper and replace it with new and then paint the paper with whatever you like.

3. Is it worth stripping all the gypsum plaster and re-doing it with lime plaster? For the modern portion of the house, there would be no requirement for the building to breathe?

If it's not damaged leave it alone - if it aint broke don't fix it! There is always a need for a house to breathe, its age and type are irrelevant.

4. Would there have been a reason why the previous owners used plain white wallpaper rather than painting? Just seems absurd to me, unless there are benefits to wall paper I am not aware of?

See answer to 2 above.

5. Is there anything I need to be aware of/any specific area I need to be careful when removing wall paper from lime plaster (if there is lime plaster in other parts of the house below the wallpaper)? Any tips/tricks appreciated

A steam wall paper stripper is often ideal but needs careful use - you don't want the plaster to become too wet. Broad bladed scrapers used in conjunction with the steam plate are the most effective hand tool but should always be applied at the shallowest angle of attack. You will need to be careful around electrical outlets for obvious reasons.

As for the specific paints on where it is lime render, Earthborn has always been positively advertised on the forum. What are the practical advantages and disadvantages of each? We just want plain white ish walls.

What are you asking about the exterior render - do you intend to paint that too?

I have no personal experience of the Earthborn paints but others do and may provide some later insights.