Pebble-dash causing damp?

benssson

Apologies for the delay in getting back - been super busy doing internal work to the bungalow.

We've decided to completely remove the cement plinth, hopefully that will help improve things.

benssson

Doozergirl wrote: »

Two 'damp specialists' with completely different ideas.

The black render is not a DPC, in fact, it's possibly the problem. The DPC is horizontal, between brick courses. The front of it and the areas around it need to be kept clear, otherwise water can travel vertically up the render, straight past the horizontal DPC and into the bricks above.

The picture isn't good, but one wouldn't usually render below the DPC. You stop the pebbledashing just above DPC and use a bell bead to kick it out slightly at the bottom, allowing water to drip away from, not down, the wall.

Below DPC you leave the brick/block uncovered. If you do render it then it's imperative it stops before the DPC and that there is a clear break.

You shouldn't have paving right up against the wall either as water can run towards the wall and settle there. There should be 150mm of clear air between DPC and the ground, and sensibly, paving should be around a foot away from the house. Lots of people fill the space between paving and wall with gravel, which allows better drainage.

What is actually happening inside the house and where though?

My poor explanation of what the second damp expert told me is pretty much what you are saying. Hopefully removing the plinth will help matters.

Inside the bungalow the room (that currently is by the plinth - to the right of the photo) has noticeably wet walls. The rest of the rooms seem fine.

ed110220

benssson wrote: »

Hi,

We've recently bought a 1970s bungalow and noticed the front bedroom seems to have a damp issue. We contacted a firm to come and take a look and he reckons its the pebble-dash letting rain soak in.

He said the pebble dash was "destoning" in that when he rubbed his had against it some of the pebbles would fall off. He then did a "test" where he poured some water over the pebble-dash and watched the quantity of water that dripped off the bottom (probably about 10-20%) to show how the pebble-dash wasn't working effectively. His recommendation is to replace the pebble-dash with a new render.

This is setting off all sorts of alarm bells and seems very "scammy" to me. The pebble-dash doesn't have any obvious cracks or sections where there are no pebbles. My gut feeling is that its a condensation issue rather than anything to do with the outside render.

Am I right to be wary?

Thanks in advance!!

Pouring water on an exterior wall as some sort of "demonstration" would set off alarm bells for me. Usually walls are designed to have some permeability so this is a bad test. Pebbles coming off sounds like a cosmetic problem.

Where is the damp inside? That might give a clue to the source. If it's high up on the wall, it's unlikely to be anything to do with a damp proof course at the bottom of the wall. Also when does it appear? If it's mainly during cold weather in winter, that would suggest condensation. Often condensation is quite obvious as it forms as a layer of water droplets on top of the paint etc.

As for the plinth, if the house has a concrete ground floor, that may be the floor slab itself, with the damp proof course directly below the render. That is how my house is and is nothing to worry about.