Tanking / waterproofing method

Jamielewis90

New Member
Hello, this is my first time posting in this site after using it for information regularly over the past year, so go easy on me.

I am renovating a 1930s ex council property in South Wales. It’s built with cavity wall bricks and the walls inside are mainly black mortar, but in good enough condition to skim over. Except for the downstairs external walls...

Two of the external walls downstairs are very damp and the previous owner has apparantly had long standing issues with this.There is yellow cavity wall insulation which I removed a small amount from one brick opening and found that it was very wet. There has also been a lot of water penetration coming through the window seals during heavy driving rain. The cavity insulation and the window seals are all being sorted on the weekend so now I want to plan what rendering methods to use to ensure that the problem is completely gone and not coming back, even if it means complete overkill on the damp proof method.

A further note that one of the downstairs rooms adjacent to the damp walls is a suspended floor.

I have currently hacked of all internal render, wire brushed loose mortar dust, and will clean the walls with a salt neutraliser and a bleach solution to eliminate salt and or mould. I am then considering tanking the walls with a tanking slurry, leaving to dry , priming with SBR then rendering with a sand and cement 3:1 mix with SBR 1:1 with water to waterproof the mix aswell.

Can any of the experts here please advise me:

Am I going to cause further problems putting all these new cement based products on a 1930s property?

Is two coats of tanking slurry a good idea and maybe what product is best?

Any other preferred methods to completely waterproof these walls and prevent any future damp?

Many thanks
 

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martinemj

Well-Known Member
Think thats bit too strong 3:1 mix and ABR overkill

If it was me...I would
Once old plaster removed and clean

Give walls coat of sand ..cement. 4 :1 mix
2 coats of tanking slurry.... Using SBR

Instead of sand cement over tanking .....use a renovating plaster such as limelite renovating
Apply limelite finish
Paint with breathable paint.....such as earthborn
 

bobski

Well-Known Member
Hello, this is my first time posting in this site after using it for information regularly over the past year, so go easy on me.

I am renovating a 1930s ex council property in South Wales. It’s built with cavity wall bricks and the walls inside are mainly black mortar, but in good enough condition to skim over. Except for the downstairs external walls...

Two of the external walls downstairs are very damp and the previous owner has apparantly had long standing issues with this.There is yellow cavity wall insulation which I removed a small amount from one brick opening and found that it was very wet. There has also been a lot of water penetration coming through the window seals during heavy driving rain. The cavity insulation and the window seals are all being sorted on the weekend so now I want to plan what rendering methods to use to ensure that the problem is completely gone and not coming back, even if it means complete overkill on the damp proof method.

A further note that one of the downstairs rooms adjacent to the damp walls is a suspended floor.

I have currently hacked of all internal render, wire brushed loose mortar dust, and will clean the walls with a salt neutraliser and a bleach solution to eliminate salt and or mould. I am then considering tanking the walls with a tanking slurry, leaving to dry , priming with SBR then rendering with a sand and cement 3:1 mix with SBR 1:1 with water to waterproof the mix aswell.

Can any of the experts here please advise me:

Am I going to cause further problems putting all these new cement based products on a 1930s property?

Is two coats of tanking slurry a good idea and maybe what product is best?

Any other preferred methods to completely waterproof these walls and prevent any future damp?

Many thanks


1 No probably not.

2 Sika or Ronafix

3 Yep.
 

johniosaif

Private Member
What I did was hack off , apply a 4/1 sbr mix with tri mix and salt neutraliser ,then a coat of triton.tt55 then a 4/1 sand and cement with trimix , on top of this I dabbed on marmox board with tile adhesive and skimmed it
 

Tinytom

Well-Known Member
Think thats bit too strong 3:1 mix and ABR overkill

If it was me...I would
Once old plaster removed and clean

Give walls coat of sand ..cement. 4 :1 mix
2 coats of tanking slurry.... Using SBR

Instead of sand cement over tanking .....use a renovating plaster such as limelite renovating
Apply limelite finish
Paint with breathable paint.....such as earthborn
Isnt it a waste of time using breathable lime lite and paint if you’ve sealed the substrate with tanking slurry and sbr which isn’t breathable (genuine question not a dig)
 

bobski

Well-Known Member
Isnt it a waste of time using breathable lime lite and paint if you’ve sealed the substrate with tanking slurry and sbr which isn’t breathable (genuine question not a dig)

Although it's a breathable product it has other properties.

It would decrease the potential of condensation as it has a thermal property too. Also salt passage.
 
when u say yellow cavity insulation, is it cavity fill? Council pumped this into lots of property's without insulation and subsequently caused damp problems.
 

Jamielewis90

New Member
when u say yellow cavity insulation, is it cavity fill? Council pumped this into lots of property's without insulation and subsequently caused damp problems.
Yellow wool cavity insulation, pumped in in 2004 I think and a remedial company who gave 25 year guarantee called CIGA have accepted that they should remove it (i thin because House is west facing and takes lots of driving rain)

Once it’s out I stil want to make the walls super waterproof just to be safe
 

martinemj

Well-Known Member
Isnt it a waste of time using breathable lime lite and paint if you’ve sealed the substrate with tanking slurry and sbr which isn’t breathable (genuine question not a dig)
Understand where your coming from....and Your right that it won't allow wall to breath

But it does go over slurry well as it's light and doesn't slump like SC
The limelite and paint would be breathable itself though so in a case of any tanking failure
Limelite good at controling salt too after curing

In a case of no or very mild damp You could miss out the slurry and just go breathable
 

Tinytom

Well-Known Member
Understand where your coming from....and Your right that it won't allow wall to breath

But it does go over slurry well as it's light and doesn't slump like SC
The limelite and paint would be breathable itself though so in a case of any tanking failure
Limelite good at controling salt too after curing

In a case of no or very mild damp You could miss out the slurry and just go breathable
Thanks mate
 
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