render replacement on terrace and pavement join

[steve_]

Hi,
After reading lots of posts and got some great info I had a couple of questions that perhaps someone more experienced in this sort of stuff could suggest . We have just purchased a nice Georgian townhouse that is in a terrace. It is also directly on the street with no front garden/separation and has a large basement.
The render on the front of the house (looks like concrete) is shot on the ground floor and needs replacing/patching. Damp is coming into the basement on the wall adjoining the street and looks to be either coming through the render where it is cracked and tracking downwards/and or is penetrating at the join of the current render and the pavement.

After lots of reading I sort of want to replace the front render, ideally with Lime render. So being a novice I have a couple of questions.

1. If the houses on either side are concrete render (as I suspect) is it possible to merge in the Lime at the house boundaries with the existing render on either side. Or will they get issues with moisture tracking behind their own render from the lime?
3. There is a natural ledge divide at the first floor, so is it possible to render from the ground the ledge with Lime and keep the sound cement temporarily above it (sounds like a bad idea perhaps)
3. At the street level what is the best way to Waterproof the join against splashback/run off. I thought about a trench drain round the base of the house covered with a slim grill (will need permission to alter the street surface), or perhaps bitumin type footings, or maybe a limecrete to act as the pointing at the point where the concrete slabs adjoin the house?

Any useful pointers welcome.

 

[Gothichome]

I may not be the best person to offer a solution, but a bit of lead flashing at the street level came to mind. Under your new render and folding on the side walk might do the trick. It only has to extend onto the walk by a few inches. It will not help if water is pooling against your wall but it should be enough to shed the splashing back on to the walk.
The up side is you probably don't need to get the council involved.

 

[george2019]

1. If the houses on either side are concrete render (as I suspect) is it possible to merge in the Lime at the house boundaries with the existing render on either side. Or will they get issues with moisture tracking behind their own render from the lime?
3. There is a natural ledge divide at the first floor, so is it possible to render from the ground the ledge with Lime and keep the sound cement temporarily above it (sounds like a bad idea perhaps)
3. At the street level what is the best way to Waterproof the join against splashback/run off. I thought about a trench drain round the base of the house covered with a slim grill (will need permission to alter the street surface), or perhaps bitumin type footings, or maybe a limecrete to act as the pointing at the point where the concrete slabs adjoin the house?

1. I think trim the cement render and run a stop bead vertically and use a sealant (brickwork movement joint style - polysulphide for exterior use) for the interface would give the best join. A lime to cement render will always be vulnerable to cracking at the interface. Moisture tracking will happen regardless, but the lime will allow for it to leave again.

2. Possible but you'd forever be chasing your tail. A large proportion of the cost (and effort) is access and getting the workers on site. Double the area won't (shouldn't) cost twice the price.

3. I'd have a good look at what other houses have done. If it's tarmac at the moment, that is hard to beat for waterproofing exterior surfaces so ingress of water may be other reasons. If water is flowing towards your houses then that's definitely something you should raise with highways but unsure what remedial actions they would take - they get a bit precious about highway drainage so they wouldn't want a trench drain going back into their system, at least not officially.
Because basements are usually damp places, if you want to make it habitable I've generally recommended internal drained cavities. Even on new builds with tanked outer walls and 'waterproof' concrete, long term, the internal cavity is gives 100% certainty that it'll be a dry space.