Repair gap between external wall and concrete slab

[Oxbow16]

Hi

 

There are some areas around my house where there's a gap between the concrete slab/path and wall.  In at least one place the water is getting in enough to make the wall wet inside the house.

 

What's the best stuff to use to fill the gaps?  

 

Should I look to fill the gap with on product, and then put in an angle section of concrete to add a second layer of protection and to direct water away?  

 

If I should be using concrete or mortar for the repairs, what mix should I use?  

 

Or am I barking up the wrong tree completely?  

 

Any advice much appreciated.

 

Cheers  

[markc]

You really need a gap between wall and path. Sounds more like a drainage problem. Is this an old house? Outside ground above inside floor level?

[Oxbow16]

The part of the house in question is a 1970s extension.  The house is on a slope, so a metre away from the wall there is a 4-5 foot drop.  So I don't think digging out concrete to create a gap would be the best idea tbh.  Outside is a little lower; I can check by how much when I get home. 

 

I should add that the problem is quite a recent one and coincides with damage to the previous repair on that gap, which makes me think the previous repair was doing it's job until failure?  

 

Cheers

[markc]

Trying to visualise this, a couple of pics would help. 

[joe90]

1 minute ago, markc said:

Trying to visualise this, a couple of pics would help. 

Agreed, sounds like youre path is above the damp course if the wet is entering the house 🤷‍♂️

[Oxbow16]

Yes, sorry. I'm at work and didn't think I had any photos to hand but turns out I have.  None show the context of the slope. But just imagine that in the first photo, the concrete slab continues out of frame to the right, and then drops vertically 4-5 feet.  Does that make sense?  I'll draw a little diagram if not.  Thanks again for the help.

 

PS - I'm presuming the long "crack" parallel to/beneath the pipe and extending beyond it is the DPC? What do you think?

 

 

 

 

 

Edited March 18 by Oxbow16

[Oxbow16]

[joe90]

Well I am guessing but your DPC should be where the render finishes, so in that case the lower section is below the DPC and may well be sucking damp up. Where is the damp showing inside?

[Redbeard]

Looks too hard and too moist.

 

If the crack is the dpc, I would hack off the render just above that level, and also look at 'softening' the horizontal surface. 

 

I take your point:

1 hour ago, Oxbow16 said:

So I don't think digging out concrete to create a gap would be the best idea tbh.

...but somehow you need to try to achieve some 'softening'.

[Oxbow16]

5 minutes ago, joe90 said:

Well I am guessing but youre DPC should be where the render finishes, so in that case the lower section is below the DPC and may well be sucking damp up. Where is the damp showing inside?

 

If the DPC was where the render finishes it would be well above the internal floor level.  Wouldn't that be incorrect? 

 

The damp is at its worse at floor level on the inside, and then forms the rough shape of a pyramid/triangle.  Around a foot and a half high.  It's centred around that crack that can be seen in pic 2; the one that's perpendicular to the wall.  

 

 

5 minutes ago, Redbeard said:

Looks too hard and too moist.

 

 

The you mean the wall, ground, or both?  

 

 

6 minutes ago, Redbeard said:

If the crack is the dpc, I would hack off the render just above that level,

 

How high - up the the roughcast?  And replace with something else or leave it exposed?  And what about the render beneath the crack/DPC?  

 

 

8 minutes ago, Redbeard said:

somehow you need to try to achieve some 'softening'.

 

Could I ask why?  If the concrete directs water away from the wall, what would be the issue?  Not disagreeing, just trying to understand.  I'd be a little scared to mess around with things so close the foundations.  Also, if there was something softer there and the water drained, I'd be concerned about where it is draining to and the possibliity of it being trapped somewhere it should be (as opposed to being able to drain freely away).  

 

 

On top of all that, it's only recently become an issue and we've been in the house over 5 years.  When we moved in there was no sign of a problem there, and that was with kitchen cupboards against the wall.  So it would seem it's a recent development.  I'd guessed it was either the previous repair failing (that peachy coloured stuff that almost looks like plaster!) AND/OR the perpendicular crack in pic 2.  

 

 

Thanks again for the great help, much appreicated.

 

  

[Redbeard]

43 minutes ago, Oxbow16 said:

Could I ask why?  If the concrete directs water away from the wall, what would be the issue?  Not disagreeing, just trying to understand. 

Contrary to what the Building Regs would have you believe (DPC should be min 150 above ext gr level) rain in some parts of the country easily bounces up 300mm, particularly off hard surfaces. If I am 'reading' correctly 300mm is about the level of that waste pipe. I had taken the internal floor level to be below that, but is it? Or is it way up by the stepped-out roughcast?

Edited March 18 by Redbeard

[Redbeard]

45 minutes ago, Oxbow16 said:

 

58 minutes ago, Redbeard said:

If the crack is the dpc, I would hack off the render just above that level,

 

How high - up the the roughcast?  And replace with something else or leave it exposed?  And what about the render beneath the crack/DPC?  

Sorry, I meant 'hack off the render *up to* just above the crack'.

[saveasteading]

3 hours ago, Oxbow16 said:

barking up the wrong tree completely?

It is almost always that the ground is too high. Can you reduce the level?

 

Why a recent worsening? More rain for sure.  Perhaps taking the wetness beyond a passable level.

some splashing from above? A previous patchup has failed?

 

 

[Oxbow16]

Hi

 

Got a few more details to add...  

 

I've measured up and the ground level outside is 230mm lower than inside (including the two layers of tiles on the inside, without those it's more like 170-180mm difference).  

 

The DPC (if it is in fact the DPC) is 160mm above ground level.  

 

 

On 18/03/2024 at 20:02, saveasteading said:

Why a recent worsening? More rain for sure....  A previous patchup has failed?

 

I'm not sure tbh, but I was thinking maybe a bit of both.  It has been ridiculously wet recently and over winter generally.  Locals say it's the wettest they can remember.  But also, as you can see in the photos, the old fillet (is that the right term?) is in quite a bad way and was possibly done in the wrong material to begin with.  There are cracks all of it, some of it is loose.  Plus there are cracks perpendicular and leading up to the wall.  So yes, my thoughts were the abundant rain and the deterioration of the "fillet" were the likely cause.  But replies here seem to suggest otherwise...      

 

Any further thoughts? 

 

Cheers 

[Oxbow16]

Good weather and a BH weekend, so hoping to get something done with this this weekend...

 

If nothing else, I was thinking to remove the existing knackered fillet, repair obvious cracks and defects in the ground-wall join with a concrete repair mastic, followed by a new fillet.  I figured and hoped that if this worked in the past hopefully it will again.   

 

I've no idea what mix of cement to use, whether to use SBR, etc. - so any thoughts on that would be great.  

 

And with the additional info and measurements I added last week, any other thoughts most welcomed too.

 

Many thanks

[Nickfromwales]

I think it’s just the general / overall deterioration of the up-stand and the floor (cracked and now U/S) as these clearly no longer perform their intended task(s). 
I doubt there will be any success in putting a band-aid on this, an instead I would pay to have this up-stand re-rendered and do the job properly. Time = decay, and maintenance & repair is the flea of owning the dog. 
Time to spend some money here methinks, sorry!

I’d only want to do this once too, so I would ask a local builder to disc cut around the perimeter of the concrete path, at around 400mm from the vertical facade, and replace that too. 
 

“Short cuts take 3 times longer and cost 3x more to do”.