Block on Flat Retaining Wall - External Render Problem

[tododo]

Hi all
I few years ago I went halves with the neighbour to sort out a retaining wall that was in a bad shape....Its sorted structurally but the render is in a bit of a state. Mainly because there is earth up against the wall. The render while not comming away or anything is just green, paint peels off and it just looks a bit of a state etc. So as its us that facing the wall I was thinking of getting some of that split faced tile .......all down the length of wall to hopefully sort it out for a good while at least. It would look smarter

The root cause is just dampness but theres not much that can be done about that now. The only think I can think of is tanking the wall in its entirity first and then tiling to give a nice finish??? Would that work do you think - I will get good flexible adhesive. I dont fancy slate as that cant be difficult getting a good bond but something that just sticks and stays there

Ill have to ask if its OK to do as technically its their wall but I dont mind doing their side either as not mcuh wall showing above their ground level

Any tips and advice appreciated

 

[freddiemercurystwin]

Some bozo suggested an idea for preventing blown render on retaining walls at the end of this thread: https://www.diynot.com/diy/threads/...-block-k-rend-and-cavity.544486/#post-4625014

 

[tododo]

Yeh - definately cant do anything on the earthy side of the retaining wall (if that makse sense) and I dont actually want render now either...just want to tile over it essentially. Is this still "the way" even for tile? Thanks though been thinking a somethng long those lines too but nice to see in a drawing

 

[23vc]

I tiled my (dense block) retaining wall, knew it was a gamble, SBR primed the heck out of it, used decent quality adhesive etc, and although most of its fine, I’ve had a couple of issues where the adhesive has just completely popped off the substrate. So I’d say it’s too risky, and would go for the FMT separation approach. Just make sure the battens are always going to be totally protected.

 

[tododo]

So battens on plastic sheet, the cement board and then tile then........will have a think, will add to the cost but its worth doing right....how far apart are the battens do you think as I know those cement boards are heavy, plus the tile so 600mm you think is enough???

 

[23vc]

More like 400mm centres

 

[Ivor Windybottom]

Treated battens will rot if exposed to running water. There's only so much that deadly chemicals can prevent before it gets rinsed away. It's wood, nature wants to eat it as it's food.

IMO the mistake was painting it. You've put something waterproof over something damp, so it was bound to get pushed off. I'd just leave it, hopefully the damp will eventually strip it all or you could help it with a powerwasher.

Besides that, is there some gravel behind it on the retained side, and some sort of drainage path - e.g. holes through the walls or a route downhill away from it? If not then it could be added with some spadework on your neighbour's side.

 

[tododo]

Yes we should have had some sort of drainage and I kinda knew it would be an issue - its a better structure than we had before for sure. It was just some sort of coal dust mixed with something to make a render from the 1930s before.....not much strength to it at all

Now the low wall is fine its just the render is a mess. I did look at drainage before we got people in and they actually recommended the block on flat.....but if we wanted to sort out properly that meant digging into next doors drive which just wasnt going to happen as they had literrally just moved in when we asked them to sort the wall out

Ive been pricing up plastic battens so we can get a gap beweteen the wall and then sheet onto that - plastic battens arnt cheap at all. 3 x the price of wood. Would anyone recommend buying plastic over wood for behind the concrete sheet - or will treated battens on DPM be OK do you think??

I got that pricing wrong for the plastic battens they costs roughly £150 for what we need and the wooden treated battens cost less than £20!!! I think bitumen the battens would offer just as much protection?

Thanks

 

[Ivor Windybottom]

Bitumen will cost most of the £150 anyway, especially if you include your time. And you'll end up with a gooey black slick under when it erodes away. Then the wood would still rot anyway.

£150 for the plastic battens sounds like good value. Use stainless steel screws and washers throughout, they cost more but you'd regret using anything else - all plated steel coatings give up and rust eventually.

 

[Ivor Windybottom]

Honestly though I'd just powerwash it and do nothing else.

 

[tododo]

If I powerwash it - I wouldnt be surprised if a lot of the render would just fall off anyway in certain areas. Was hoping to get away with wood but your are right!

 

[tododo]

Just a quick one hopefully - trying to source stainless steel cement board screws......but there are none that ive found yet....would you recommend using non stainless steel (specific for the job) cement board screws outdoors (zinc coated) or would it just be better to use standard stainless (non cement board) screws instead. I think im leaning to the latter to be honest.

 

[Ivor Windybottom]

Use stainless insulation board washers together with stainless countersunk head woodscrews.

E.g.

Buy TIMco MID36SS Stainless Steel Metal Insulation Disc Washers 36mm

Large diameter disc insulation washers, for use with screws to hold insulation materials to battens. They can also be used for cracked ceiling repairs. These insulation washers have a 5.5mm diameter hole in the centre. They do not come supplied with screws, meaning you can use the desired length...

www.tcfixings.co.uk

Lots available all over the place. Avoid galvanised (rusty) or plastic (too thick) ones.

 

[tododo]

arh those things - brilliant thanks again