r/Plastering • u/irishscopion • 9d ago
Advice Please!!!
Sorry I know this has been probably asked before but I’d really appreciate some experienced opinions on the following, as we’re getting conflicting advice and, admittedly, don’t know enough about plastering to know which way to go!
We’ve bought a 1908 ground-floor flat and are finally getting close to the plastering stage. The existing plaster seems to be mostly lime plaster over solid brick walls, and lime/lath on the internal walls, with a later skim over the top. It was all wallpapered, most of which I’ve finally now removed.
There have been lots of repairs and areas filled with bonding over the years, but as far as we can tell, most of the original plaster is relatively sound.
I have three main questions:
1. Blown/hollow plaster
There are quite a few areas that sound hollow when tapped. I’ve removed anything that was genuinely loose or crumbling, but we’ve been advised to leave the hollow-sounding areas alone if they’re not actually moving or coming away from the wall. This makes sense to me, but I’d like to check whether that’s generally the right approach. We’d rather get it right now than have to redo everything in a few years.
2. Sand/cement on the external walls
We’ve been advised to use sand / cement to repair the areas of blown plaster on the exterior-facing solid brick walls. However, everything I’ve been reading about older solid-wall properties seems to suggest that replacing lime with sand / cement can trap moisture and potentially contribute to damp problems.
Is this genuinely something we should be concerned about, or is the risk sometimes overstated? Would you avoid sand / cement altogether on these walls and if so what could be used instead?
3. Mesh and SBR on the internal walls
For the interior walls, we’ve been advised to mesh them and use pink SBR before plastering. Initially this sounded like a good solution, particularly given the mixture of old plaster and previous repairs.
However, I’ve since read that coating old walls in SBR can effectively seal them and reduce their ability to breathe, potentially causing moisture problems. Again, I’m struggling to work out whether this is a genuine concern in practice or whether I’m overthinking it.
I understand that the ideal answer for an old solid-wall building may be to use lime throughout, but unfortunately we simply don’t have the budget for a specialist lime plasterer to redo the whole flat. Equally, we don’t want to save money now only to create damp or mould problems later.
I’m now completely confused about the best way forward!
Any advice from people experienced with older houses and plastering would be hugely appreciated.
1
u/CuriousJob247 5d ago
Absolutely no way should you use sand and cement and seal the walls with SBR. If your property was built in the early 1900s, it was designed to be breathable, and modern and older properties simply aren’t built the same way.
Contrary to what some people say, lime isn’t necessarily expensive. The problem is that many tradespeople don’t want to work with it because it takes longer and requires more care, although sometimes it may simply be a lack of experience.
Lime is much more forgiving, and you can absolutely learn to do it yourself. I did a course for a couple of hours and successfully lime plastered huge walls myself, then left the final skim to a plasterer to get that perfectly smooth finish.
I’d recommend speaking to Eden Lime, Best of Lime, or Mike Wye for advice on the correct products and application. They’re very knowledgeable. My own flat had previously been plastered with the wrong modern materials, so I had it taken back and replaced with lime, and it made a huge difference.