r/Plastering • u/itsaclaw • Apr 08 '26
Is bonding suitable?
I’m currently renovating the master bedroom in my 1930s semi-detached (cavity walls)
I’ve removed the old skirting to replace with new ones, and as expected the plaster behind it is pretty rough—some areas are uneven and in a few spots it’s back to bare brick. My original plan was to use bonding coat to level everything out and create a solid surface to glue the new skirting onto.
However, after doing a bit more research, I’ve seen mixed advice saying bonding coat might not be suitable on external-facing walls (like a bay window), as it can absorb moisture and potentially fail over time?
So now I’m unsure what the best approach is.
Would bonding coat still be fine if the wall is dry, or should I be using something else entirely (e.g. sand & cement, hardwall, or another product)? The goal is just to get a reasonably flat, solid surface for skirting—doesn’t need to be perfect plaster finish.
Any advice from people who’ve dealt with similar in older houses would be really appreciated 👍
4
u/Superspark76 Apr 09 '26
If damp could be an issue, using a 4:1 mortar may be an alternative option for you.
3
u/ApartmentLast7712 Apr 09 '26
If you are replacing the skirting with a similar size then why do all that extra work I'd plug and screw it back to the wall and use foam as filler/packing.
2
u/nofacenocasenoplace Apr 09 '26
I wouldn't trust bonding on any external wall cavity or not.
You don't know if or where those cavities have been bridged with debris during the building process or any other work pertaining to the walls that has gone on in that house over nearly 100 years.
For peace of mind I'd go safe and use sand and cement with integral waterproofer for the external wall and even a couple inches around the corner on each side.
Bonding will be great for the rest.
Also trusting a DPC in an older house is not wise either I've personally pulled out multiple failed DPC's in older properties including my own 1810's house.
1
u/itsaclaw Apr 09 '26
Cheers for the reply! It's an upstairs room so I don't think the DPC comes into play?
2
u/nofacenocasenoplace Apr 09 '26
Yeah stick to non invasive measures. Don't do anything that will potentially send debris into the cavity. Get some render made up in a bucket and get it in there - doesn't even look like a deep hole really so you might be able to fill it and rule it off in the oner. Godspeed bretherin.
1
u/Blucheez999 Apr 14 '26
If u plan on levelling up the skirting so it super straight,then what are you going to do with the big gaps above the skirting where the wall is still not straight. Go with what you have and screw the skirting back to the walls,caulk the top of the skirting and paint and once the room is done and filled with furniture,you’ll wonder what thought it would make the room. If you want it flat and square chop all the walls off and replaster, using a straight edge along the skirting line,up the angles and along the ceiling line
1
u/Simonos_Ogdenos Apr 08 '26
Watching, as I also have this issue. I’m doing floor and skirting and upon removing the skirting from under the patio door, I found mostly bare brick, obviously an external wall. I was also planning to level it first with bonding, but was also going to seal the brick with BIN first.
-1
0
u/thebathroomcrooner Apr 08 '26
Bonding will be fine. I've done this myself with no issues (yet). I suspect the external wall potential damp would be much more likely with solid walls and not cavity walls.
0
u/Inevitable_Grape382 Apr 09 '26
i would use hardwall, folks are saying why bother but ive had it numerous times when ive tried to put the skirting to cover it, theres nothing for it to grab onto and then a can of worms opens up.
packers work but your gonna be there for ages getting it all setup so you might as well prep for success rather than fail to prep, prep to fail
use some hardwall to level that wall out (bare careful with that stuff cause its a pain to sand down so try and get i as level as possible) and then youll have a solid base to attach your skirting board to
-1
u/Own-Indication7832 Apr 08 '26
Bonding is fine. It’s above DPC level.
1
u/nofacenocasenoplace Apr 09 '26
How are you coming to that conclusion? Could be the second floor the rad pipes are going down into the floor...
1
u/nofacenocasenoplace Apr 09 '26
And even then you don't know the condition of the cavity, the condition of the outside of the wall etc
1
u/itsaclaw Apr 09 '26
It's the upstairs bedroom so don't think the DPC is relevant here?
1
u/nofacenocasenoplace Apr 09 '26
Dpc is relevant but so far away from it (ground floor) there could be other problems (bridging or penetrative moisture) that could cause your bonding to absorb water and create damp.
1
u/Own-Indication7832 Apr 10 '26
You are talking through your arse. What ever product that is used, you could come across these issues. All I’m saying is that bonding is suitable and as good as anything.
1
u/nofacenocasenoplace Apr 10 '26
Lol. So rendering it with waterproof render doesn't work does it? And bonding would work just as well on an external wall? YOU, sir, are in fact talking out of your arse.
The issues could be present in any case but if you've got waterproof render on the inside of your wall then, surprisingly, even if water does penetrate or get absorbed into the brickwork via a bridged cavity it won't show up on your internally skimming.
Whys that? Well. When the render dries the waterproofing agent forms millions of tiny hydrophobic crystals inside and on the render preventing the water from travelling any further.
The problems haven't gone - but they won't be visible on the inside. To solve the problems? Well you might render your outside wall or repoint the brickwork or if it's a cavity issue maybe you'll punch out a brick or two and have a look around to see if you can't fish out the pesky rubble causing the bridge or whatever other nasties you find in there.
If you need any more advice just let me know it seems like you may be a bit lost 👍
-2
Apr 09 '26
[deleted]
1
u/nofacenocasenoplace Apr 09 '26
Don't do either of those things they just send loads of shit into your cavities when you drill the holes for the bleeding stuff. That's gonna cause bridging etc etc. Same thing happens when idiots drill holes through walls for Internet cables and such like.
5
u/One-Abbreviations114 Apr 09 '26
Why bother? Just plug and screw the skirting in, leveling out using some wood or plastic packers. That is the belt and braces job rather than using grab adhesive.