dot and dab over soot on bricks

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Jonathand

New Member
hi all

i've removed a chimney breast upstairs and down and have soot deposits on the walls. im dotting and dabbing the whole house so want to do the same on these walls, because i can do it quite well and i'm terrible at plastering otherwise and it's cheaper for me to D&D and then have it skimmed then have a plasterer do it all.
downstairs wall.jpg
upstairs wall.jpg


i will mechanically remove as much of the soot as possible and then...

ive read up quite a bit on line, both on this site and others and it seems my options are:
1. batten the wall - i don't want to do this as the bricks are hollow and drilling and fixing is a nightmare.
2. D&D Gypsum MF10 metal channels to the wall and screw board to these
3. render the area +300mm either side and then D&D over this

the plasterer that will be skimming to me to get some soot inhibitor, but no idea what he's talking about and can't find anything of this description online.

the MF10 channel would be easy to do but a bit pricey at £50 for 10 lengths.

where it gets tricky for me is the various suggestions for rendering i've read and knowing which i should do. coats of SBR first, slurry or no slurry, render with SBR in, Render with lime in, one coat of render or two etc. i'm a bit at sea with it all! and there are so many products out there that seem to do the same thing in terms of tanking or waterproofing.

can anyone give me some clear advice on the steps i would need to take to seal the wall via rendering prior to D&D to stop damp and staining coming through? the surface is very uneven where the tied-in bricks have been cut through, as per photos. It's a party wall, if this is relevant. the whole wall on each floor is 2.5m high and 3.1m wide. the chimney breast was 1.1m wide.

thanks in advance.
 

ChrispyUK

Well-Known Member
hi all

i've removed a chimney breast upstairs and down and have soot deposits on the walls. im dotting and dabbing the whole house so want to do the same on these walls, because i can do it quite well and i'm terrible at plastering otherwise and it's cheaper for me to D&D and then have it skimmed then have a plasterer do it all. View attachment 49929 View attachment 49930

i will mechanically remove as much of the soot as possible and then...

ive read up quite a bit on line, both on this site and others and it seems my options are:
1. batten the wall - i don't want to do this as the bricks are hollow and drilling and fixing is a nightmare.
2. D&D Gypsum MF10 metal channels to the wall and screw board to these
3. render the area +300mm either side and then D&D over this

the plasterer that will be skimming to me to get some soot inhibitor, but no idea what he's talking about and can't find anything of this description online.

the MF10 channel would be easy to do but a bit pricey at £50 for 10 lengths.

where it gets tricky for me is the various suggestions for rendering i've read and knowing which i should do. coats of SBR first, slurry or no slurry, render with SBR in, Render with lime in, one coat of render or two etc. i'm a bit at sea with it all! and there are so many products out there that seem to do the same thing in terms of tanking or waterproofing.

can anyone give me some clear advice on the steps i would need to take to seal the wall via rendering prior to D&D to stop damp and staining coming through? the surface is very uneven where the tied-in bricks have been cut through, as per photos. It's a party wall, if this is relevant. the whole wall on each floor is 2.5m high and 3.1m wide. the chimney breast was 1.1m wide.

thanks in advance.

Squirt of water on the wall and crack on. Don't think what little bit is left will cause you a problem.

Btw, are you an engineer?
 

Wayners

Well-Known Member
I'd grind off soot as best I could within reason. Maybe use wire brush. Zinsser cover stain over the soot area. Leave for 24h then dot and dab as normal
 
Last edited:

Monkey Boy

Well-Known Member
What Wagner’s said if your worried about staining coming through
What bof said if your worried about a chemical key fail

Or - Insta stik foam the boards up and let me know if foam alone stops staining coming through
 

ChrispyUK

Well-Known Member
I may be wrong and will happily be corrected, but how is soot getting through a dot and dabbed PB?
 

Monkey Boy

Well-Known Member
I may be wrong and will happily be corrected, but how is soot getting through a dot and dabbed PB?
Black carbon in soot is very fine particulate mater that can work its way in or through substrate but there needs to be a driving force. It don’t just walk.
Where a wall will breathe that can drive it
Me thinks?
 

bof

Well-Known Member
The question might be

Will contaminates from fired bricked have potential problems with the dab and it's fixing

The other question is

I've just soaked 10 Afghan hash type seeds and one blueberry kush ( for the novelty )
Drained them to sprout on tissue paper , one stuck to my finger and dropped on the gravel floor , on inspection it's the novelty seed lol
Do I water the area with a blanket on top for a few days to see if it sprouts or have a lye in and pretend I'm ringing Wickes and bnq for customers in search of multi
 

ChrispyUK

Well-Known Member
The question might be

Will contaminates from fired bricked have potential problems with the dab and it's fixing

The other question is

I've just soaked 10 Afghan hash type seeds and one blueberry kush ( for the novelty )
Drained them to sprout on tissue paper , one stuck to my finger and dropped on the gravel floor , on inspection it's the novelty seed lol
Do I water the area with a blanket on top for a few days to see if it sprouts or have a lye in and pretend I'm ringing Wickes and bnq for customers in search of multi

The latter.
 
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The Hobo

Well-Known Member
Cow s**t good on soot
The question might be

Will contaminates from fired bricked have potential problems with the dab and it's fixing

The other question is

I've just soaked 10 Afghan hash type seeds and one blueberry kush ( for the novelty )
Drained them to sprout on tissue paper , one stuck to my finger and dropped on the gravel floor , on inspection it's the novelty seed lol
Do I water the area with a blanket on top for a few days to see if it sprouts or have a lye in and pretend I'm ringing Wickes and bnq for customers in search of multi
ask monty don on the gardeners forum
 
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Reactions: bof

Jonathand

New Member
I'd grind off soot as best I could within reason. Maybe use wire brush. Zinsser cover stain over the soot area. Leave for 24h then dot and dab as normal
I emailed zissner about using the stain block for blocking soot. Their reply was B-I-N is more suitable but it can't prevent salts coming through.
 

Jonathand

New Member
I may be wrong and will happily be corrected, but how is soot getting through a dot and dabbed PB?
Soot contains high levels of salts that are hygroscopic. They will absorb moisture from the air, which will then travel through the dabs to the plastered surface and produce a brown/yellow stain. Just the same as when there's been rising damp, but different salts.
 

ChrispyUK

Well-Known Member
Soot contains high levels of salts that are hygroscopic. They will absorb moisture from the air, which will then travel through the dabs to the plastered surface and produce a brown/yellow stain. Just the same as when there's been rising damp, but different salts.

I’m aware of that, but wasn’t sure if they’ll travel through a layer of plasterboard.
what about a coat of S + C with waterproofer in or a spread of rapidset tile adhesive just over the sooty areas.
 

Jonathand

New Member
I’m aware of that, but wasn’t sure if they’ll travel through a layer of plasterboard.
what about a coat of S + C with waterproofer in or a spread of rapidset tile adhesive just over the sooty areas.
The moisture will go into the dabs and plasterboard loves water, will soak it all up. What's S+C?
 

Vincey

Private Member
I’d float the wall anyway and the guy is right cow shot to remove the soot believe it or not
 

John j

Mono Don
Good brush
Then water or week pva.


Anyone used this.builder gave me it to use so I could dot on to gloss paint. Let you know Thursday if he was righy
IMG-20201018-WA0005.jpeg
 
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