What's wrong with my render?

[Ozmi]

This render was new 5yrs ago (it's an extension). It directly abuts the concrete drive (which was there first). The drive slopes away reasonably steeply. The render appears to have a network of micro-cracks & some flaking. I think I even saw a fine white fluffy mould on it in places before now. To the left-hand corner is a downpipe that discharges onto the drive. The rust lines are from iron deposits in the new pebbledash - unrelated.

Due to a staircase, the interior of this room is about 18" lower than the drive (in case anyone thinks of airbricks) and the floor inside is concrete.

The pebbledash is fine.

Bumping for the weekend crowd

@Pigletjohn will advise if he is around, but my guess is damp. There is no gap from the end of the render and the ground which there should be. Also, when not damp, paint will flake if the render hasn't been treated with a stabiliser first

My guess would be that there is damp trapped in the wall. Either the render or the concrete are breaching the damp proof and there is nowhere for the wall to breathe to. Is the inside lime plastered?

Crikey, I need to change my glasses…. I read that as “what’s wrong with my reindeer?” 😳

Sorry, OP 😄

the cracking seems to be in the smooth plinth.

the pebbledash does not look cracked, perhaps because the stones break up the surface and discourage crack growth.

it might be that the wall is built of lightweight blocks and they expand and contract at a rate different to the render. it looks like the bottom of the wall will get wet in rain, and (hopefully) dry out in dry weather or sunlight. If the wall was built of bricks they would look better exposed, so probably not.

It's undesirable to have the wall of a partially basement room in contact with the ground and paving, because it will promote damp. Is the inside wall damp? Do you know if steps have been taken to protect against damp?

The cracking pattern suggests the plinth is coming away from the wall in broken pieces like crazy paving. Perhaps the mix was bad or is not adhering properly. If you tap it with your knucles, does it sound hollow? It might also have been loosened by water freezing behind the plinth and pushing it off. I don't see a drip on the bottom of the pebbledash to throw off water, and the plinth actually projects so that water will lie on the ledge and soak in.

scrape the paint off the plinth to encourage evaporation from the surface. When the plinth falls off you can have it done in a plain mix, not painted, you can use white cement and white sand if you want.

p.s.

"white fluffy mould " is probably efflorescence, especially if you are in a hard water area. If you see it again, take more pics. Scrape some into a jar and drip vinegar on it, it will probably fizz. It is not harmful but is the result of damp drying out.

Stand back and take a wider pic to include gutter, downpipe and any drains.

@PigletJohn & thanks

The wall is made of those large grey blocks. It was waterproofed all around with some kind of full-size thick plastic sheeting. There is no damp on the inside. I knocked all over the plinth and it's sound, there's no hollow loose areas. It actually feels rock solid, it's not crumbly, though the paint is definitely peeling. There are no hairline cracks in the Pebble area.

"I don't see a drip on the bottom of the pebbledash to throw off water" - the top of the plinth is angled to shed water.

Two things come to mind. 1) was the plinth made of the correct render mix? and 2) Could it be missing some kind of bonding coat before painting?

Can I do anything over the summer when it's very dry to improve it? (sand, fill, PVA & paint?) Also, should the downpipe be diverted to discharge directly into the drain?

it would certainly be preferable to have the downpipe empty into the drain. There seems to be a nearby gulley. The change should probably start at the top. Post a pic that goes right up to the roof and gutter and shows all the pipes. please also look down and photograph the gully. is it plastic or glazed brown clay like a teapot? how old is the house?

I don't know what sort of plastic sheeting you have. There is (at least) one waterproof lathing made with a key to hold render or plaster but I am not familiar with the technique. If you have any plans they might say.

I wouldn't bother patching up the render. Scrape the paint off to help it dry and keep an eye on it.

@PigletJohn

The drain gully on the left is brown glazed, the house is '20s.
'B' is the bathroom basin waste pipe
'S' is the toilet soil pipe.

From what it looks like I need, there's no tidy way to join the guttering to the drain as both the soil pipe and gas meter are in the way. Now you can see the set-up, how far up the guttering downpipe do you think is the best place to cut into it to direct it to the drain?

A diagonal could run under the little window, it would look rather unsightly. A gutter in the concrete slab would also look bad.

But since you have a glazed clay gulley on a 1920s house, it is pretty sure to be cracked, broken and leaking in the ground. So when you have it dug out and renewed, you could perhaps add a new gulley under the little downpipe.

If you tilted the gutter to slope down to the right, is there a nearby drain on that side?

Update

Oh that's an iron manhole cover?

I thought it was a doormat

Lift it up and see if both the rainwater and foul go into it. This is no longer allowed but used to be done (combined drainage)

If so, the downpipe could connect to it.

It would mean digging up the concrete and you had better find out if a new extension is allowed to connect to old combined drains. Your local water company or council probably has byelaws. I don't know.

If you have to dig up the concrete I would be tempted to take up the whole lot, renew any defective drains, and perhaps put a gap and a French drain or a metal gutter through against the wall with the plinth. 1920s concrete is usually quite thin.

Sorry I am growing the size of the job.

Maybe wait until the concrete cracks or you see wild tomato plants?

If you tilted the gutter to slope down to the right, is there a nearby drain on that side? Immediately to the right is an 18" drop down to the neighbouring driveway.
The gullies beneath the manhole were inspected & passed at the time of the build but also recently by the water company who were inspecting the whole street and they are correct.

I see this could have been better planned but I was unaware of drainage issues at the time of construction. I think I'll create an ugly but purposeful dog-leg in the gutter downpipe & get it directly emptying into the drain. As much as I'd like to replace the drive, I think breaking out all that concrete (Our house is higher than next door) would wreck their new (bonded resin pebble) drive which goes right up to the edge of mine. Many thanks for your thoughts @PigletJohn

Can I ask, is there a specific gradient which is best for channelling water from the gutter to the drain? I suppose as steep as possible is desirable?

gutter slope of half an inch per ten foot is fine

quarter inch may do but perhaps accumulate leaves

too extreme a slope makes the house look like it's leaning.

oh, you mean the downpipe?

The actual diagonal fitting is called a 112.5 degree offset bend or a branch.

downpipes are deliberately made a bit loose so you have a bit of wiggle room (they are not sealed)