removal of concrete render and repair of brickwork

[abinath]

Hi
On a 9 inch brick wall of a 1919 house, on the ground floor, I have some penetrating damp coming inside due to water getting behind damaged render. I intend to cut the render horizontally 6 feet above the ground, and remove the lower 6 foot of it.
The brickwork is likely to be damaged. I will dub up any damage to bricks with a concrete mix, and repoint as necessary, and finally apply a water-repelling breathable paint.
My concerns are:

- Given that I cannot work continuously, the wall may be exposed to rain (its facing SW hence takes rain head-on) for a few weeks. Should I be concerned about rain soaking into the wall (and penetrating to the inside) before I can apply the paint ? - should I attempt to protect the exposed lower section of wall from rain, and whats the best way ?

- Is there any breathable water repellant compound that can be used on damaged non-smooth brickwork ?

- Is there any particular mix most suited to dubbing out damaged bricks ?

- Should I be particular about the mortar used when pointing ? (given that the original mortar was probably lime based?)

- Should I think of applying a bead to the bottom edge of the remaining render in an attempt to deflect rain from the wall below ?

Thanks

 

[tireetim]

I'm not the man to answer your questions but I have a similar problem and would be interested to hear the answers. Has the render bridged the DPC causing the water to soak up between the render and the bricks? This has happend on mine and I've been advised to cut the render away to above the DPC and put in a stainless steel bell cast.

 

[abinath]

Hi Tireetim

Yes it seems you have a similar issue.
I am planning to take an angle grinder to do a horizontal cut 6 foot above the ground, then remove the render below that level.
Hope the brickwork is not badly damaged.
I will then dub out any damaged bricks and repoint as necessary.
I then need to decide whether to apply a water-repellant breathable paint, OR render with k-rend.

Can private messages be sent on this forum ?

Regards

 

[tireetim]

You can send pm's but only to people you are friends with. I've sent you a request if you want to pm.
What is the reason for taking the render back so high? Is it to fix damaged bricks? I was only planning to go to just above the dpc. Below the render line on my house the bricks are painted in what I'm assuming is (or was) a waterproof paint. It's a sort of teraacotta colour. All the houses in this area are the same and it's also used on some of the houses to cover the steel lintels above the windows. I was going to try and find something similar and re-paint it once I have re-pointed all the exposed brick work.

 

[cotswoldbuilders]

Id treat the walls with an sbr slurry mix, ( follow instructions on container ) prior to a scratch coat then float coat.
Don't forget to add some water proofer to the mix.

 

[tireetim]

thanks cotswoldbuilders. Can you just add more SBR to the scratch coat instead of a waterproofer? I bought some SBR for a different render job and I'm sure the instructions were to paint on a slurry mix then first coat with SBR included. Haven't got around to doing that yet but would be good to know from somebody with experience !

 

[abinath]

Hi Tireetim
I need to remove around the bottom 6 foot because below this the concrete render has blown and is clearly letting water in. When its off, I need to decide whether to paint with a breathable paint or render with k-rend. No doubt there will be some repairs to do first. I will have a gable end with k-rend on the lower 6 foot and concrete render above but I can live with that. Dont want to put concrete back on.

Cotswoldbuilder - I have been advised not to apply any kind of paint or water-repellant to the walls before rendering, because the render would then fall away. Is SBR an exception to this ? Does it colour the bricks or is it transparent ?

 

[tireetim]

OK, didn't realise the render was so bad !
SBR is mixed with cement and painted onto the walls (really thin) to act as a bonding for the render. They call it a slurry mix. It's also waterproof. You then mix SBR into the render mix to make the render waterproof and it also strengthens it. Not sure how different this would then be to k-rend as never used it but it sounds like if you wanted to keep the gable end uniform you could use the SBR method instead of the k-rend. Please bear in mind this is only what I have read and information that I have got from builders. I have never used either product myself !

 

[abinath]

This is interesting thankyou Tireetim.
So is SBR / concrete mix truly an alternative to rendering or painting ? It would have to be coloured or opaque if any bricks had been dubbed out, otherwise the wall would look a mess.
I was wanting to have whatever covering I did apply to be breathable, hence the k-rend. However if there is a waterproof coat that is reliable and robust, perhaps that is the way to go. The SBR / slurry mix appears to be such that you can render over it at a later date if you wish (unlike paints or limewash say which wont accept render) but if I am looking for a breathable render that wouldn't make sense because the SBR / concrete mix won't be breathable.