Remove cement render?

[january29]

Looking for advice on the start of my damp journey in our Edwardian home. Survey suggested walls are damp with ‘high readings’ and there’s one patch which is damp as plaster is blistering. So starting to look outside would it be best to remove this cement render around the base of the bricks?

i'm no expert but I would think that is bridging the damp proof course, and therefore enabling damp in the ground to rise up into the walls. Most rendering I've seen is higher up and stops below the top level of the rendering in your photos ie the opposite of what you have.
I've also read somewhere that when you remove render it can take the outer surface of the brick with it.
I would try and get a few expert opinions and then proceed on the advice of who seems most trustworthy - there are some odd treatments for damp being sold that appear to be useless, apart from making money for charlatans.

Thank you that was my first thought! @pigletjohn do you have any wise words?

The render should have a bell lip for the water to run off. It shouldn’t go down to the ground. Find the DPC. Re render to stop above that with a lip. Expose the bricks underneath. Clean them off and repair.

the aitbricks look to me like modern additions.

the cement plinth was probaby intended to hide (it does nor repair) damp.

Look for the orifinal damp course. Probablt two layers of slate in a fat mortar bed, nine inches above where the ground used to be when the house was built. It may be visible under or beside a doorway opening. Follow it along the wall with a chalk line. It will usually be at the same height all round the house. Is it below, above, or covered by the plinth?

can you see any damp patches? Are they close to drains?

p.s.

all the shrubs I can see in that strip of recently-dug earth next to the house look new. It might be that somebody has recently done some work and hidden it. If they have removed old concrete or paving, it would have shown sinking or cracks where the ground has gone down around a drain leak (which is very probable in a house of that age, and a common source of damp patches).

Please photograph the inside and outside of your damp paches, and any drains, downpipes, leaking gutters, and especially gullies close to them.

Thanks @PigletJohn so I’ve been out and there’s only one place further round the house where there’s possible evidence of original damp course following this line around all the rest would be covered by the cement.

Here are further pics of the damp inside and outside

Inside

So in your dampcourse pic, is it at the top of the plinth?

Run some chalk along to make it show better.

Some of the plinth looks like it was applied with a spoon, so probably covering up damage.

I would suspect that gulley has had brickwork added round it. Get your trowel out and see if the ground near it is wet or has red worms in it. If it is leaking it will usually have sunk into the ground and you may see attempts to use the surround to get nearer to the downpipe.

The wet near your electrical socket, what is on the outside at that exact point? Is it a concrete floor or wood?

Dampcourse with chalk, I’ve found two possible damp courses, one just at the top of the plinth and one higher above. If I follow the lower one it would be covered over by cement as it went round, the higher one would be clear of it but I can’t see any evidence of the higher one further round the house.

This is the wet wall, the socket is below the window, it’s part of an extension some point I believe as the floor is concrete.

Feeling a little confused with it all! I also have found documents to suggest over 30 years ago rent o kil have ‘helped’ but again I can’t see evidence of where they have been.

The wall under the window looks dark. It might be the brickwork is damp, or it might be that the sill protected it from the weather. Could the gutter above be dripping?

When you have a damp patch at the bottom of a wall with a concrete floor, the damp may be in the floor, often when an old pipe is leaking. Have a look under the carpet. Lie a piece of clear plastic on the concrete, and in a week or so, look to see if water has accumulated under it, as it cannot evaporate away.

I'm very interested in the gulley and the downpipe, as they are delivering water nearby, and there may be a leak into the ground.

Can you do closeup pics of your dpc? Use a stiff brush to clean away dust and loose mortar.

Rentokil might have added those new-looking airbricks, or possibly done chemical injections. Airbricks are very good for drying underfloor voids, but no help with concrete floors.

I’ve been out watching the rain and discovered the gutter is a couple of inches short and therefore dripping at the end. I’ve replaced so hoping that may help.

I’ve laid some plastic on the floor so will report back.

How would it be best to figure out if the pipes are leaking underground? I can see no obvious above ground evidence. I’m also still concerned the cement render bridges the line of the dpc so am thinking about removing a small section.

Someone’s added cement so this is closest dpc pic I could take.

Also I’ve now discovers both fireplaces have evidence of damp at the bases. But I’m thinking that’s a different issue?!

Fireplaces need to be ventilated top and bottom.

However, if the slab is damp, there is probably water in the ground. The slab does not usually have a DPM and lies on mixed rubble and earth.

Your photo is of a double slate bed which is very effective, but has been bridged by the mortar plinth that was probably applied to hide long-term wet brickwork.

Look at nearby drains especially clay gullies.

Fixing the gutter may make a big difference. Chalk round the boundaries of the wet mark, photograph it with flash, and again at intervals, see if it gets smaller. You may find white lime bloom forms as it dries out, this is the time of year for it. If you look at sunny walls in your town this week you may see other cases, especially on garden walls and new builds.

To detect a water supply pipe that is leaking, first find your external stopcock or water meter. It will probably be near where the front gate used to be when the house was built, and in a straight line to where the kitchen sink used to be when the house was built. There may be a small iron lid over it, or a tile, or some idiot may have laid concrete over it. Dig out the mud, slugs and newts.

Put a young person with good hearing in the kitchen late at night when all is quiet .

Turn the external stopcock on and off repeatedly.

The noise of a leak is faint white noise and you will not notice it. But you will notice if it stops and starts.

@PigletJohn PigletJohn still working on my damp issues! So I’ve not got the right tools to start removing the outside cement render plinth. I have taken of a section that was hollow/not properly attached. The bricks began drying out in minutes. Now my question is should I remove the render below the damp proof course or just focus on removing so I can see the dpc?

remove anything bridging the DPC most urgently. It is usual to remove the render above the DPC as your second priority, so the bricks can dry out.

I personally would also remove the render below the DPC, but this part is "allowed" to be damp, and the bricks may have spalled due to frost, so they may look unsightly when bare. I don't know if a lime mortar render below DPC would be acceptable. I will see if I can find an example locally. I don't remember seeing one.

IME water will only rise about two courses of clean, bare brickwork, above ground level. But there might be plaster on the inside face, or a cavity filled with damp rubble, which will encorage water to move by capillarity.

What tool are you using?

A bolster and a club hammer are the simplest and cheapest tools. Wear substantial gloves and choose a bolster with a protective collar. You will hit your hand.

bolsters
you can get bolsters up to about 150mm wide. 75mm is a good start, because you can also use it for electrical backboxes later

It is absolutely ESSENTIAL to wear eye protection, and I strongly recommend ear protectors.

Club Hammers. If you are a bit weedy, get a lighter one.

p.s.

when using a club hammer, try not to grip it, or the bolster, with great tightness or to bash hard and fast. This leads to Golfers Elbow or Tennis Elbow. Take rests. I should think a 1kg hammer will suit you.