Rising damp or condensation?

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The internal plaster has been flaking off a large area of our north facing living for some time now.
This is an extension built before us - maybe 10-20 years old.
The damp is also appearing low down on what would have been the old outside wall but is now the wall edge of an internal fireplace (third pic).
Before winter we did insert those silicon injections ourselves incase it was rising damp. Have also re done any holes in the pointing again as there were quite a few. There was a large hole behind the tv wall (2nd pic) half way up which is now filled in.
I have resealed the French drains as the joints were letting water through to the ground. I have also sealed all the walls outside with breathable wall paint seal.
Is this enough?
Had two plastered around to quote on re plastering . I have asked for breathable plaster. They wasn't sure what would have been causing the damp and we're worried the new plaster would just come off again.
There is no ventilation in the living room and we do get a lot of condensation. Could it be internal condensation reacting with bad plastering and metal beading etc?
I'm not sure where to go from here.
@pigletjohn I know you are an expert if you or anyone else could offer some ideas of what we could do next thank you.

Pics

More pics

This is the outside of the to wall

is it a concrete floor?

can you see the dpc?

have you got a water meter, and a person under 20 with ears in good condition? do you know where the outside stopcock is?

Is it possible that it is the cill that is letting in water under the window? It doesn’t seem to be happening in the wall to the left of the windows. Is it? A very poor cill detail could let in water from the outside.

Otherwise yes possibly riding damp?

When you say French drain do you a mean a trench with a slotted pipe wrapped in a geotextile and filled with a gravel surround? They tend to be used at retaining walls it is actually quite unusual to have them at the edge of a house/wall unless the outside level of the ground is higher than your floor level inside? Is that what you have? That can result in damp issues and the French drain may not be doing it job anymore. The geotextile can get clogged with silt.

I personally don’t think it is condensation from that picture.

the thing in the pic is not a french drain, it is a gutter. it would be interesting to know why a house needs a gutter round it. does the paving slope towards the house, causing rainwater to run to it?

Oops just saw your updated outside photos, an aco channel not a French drain. I would say there might possibly be a leak from the drainage that is causing an issue. The white on the brickwork is minerals leeching out of the brickwork efference (can’t spell sorry) while it is normal to get some due to rain the position of that at the lower level looks like something caused by excessive water at that location. I think the drain might be damaged. It could be a dpc issue either though.

I definitely do not think it is condensation.

Thank you all for replying.
Yes inside is a concrete floor. Outside there seems to be dirt underneath the patio.
Yes the dpc looks in good condition two bricks up.
Have access to the water meter but not sure where the outside stop cock would be?
There shouldn't be any pipes underneath that extension so don't think it's a water leak.
The seal underneath the window looks in good condition and this is starting to happen on the left wall too. Also window seal wouldn't explain behind the wall behind the tv? As no window there.
Unless multiple different issues?
The floor gutter (French drain!) is concrete and assume it was put there when the extension was built.
I have filled in the holes between the 'gutter' joins before winter. It was previously leaking and draining underneath - could this now solve it?
The garden is two levels - I will try to post a picture.

Outside garden picture. Is it all draining into my wall from the grass when it rains?
The patio isn’t particuarly angled to the floor gutter.

A damp meter would be able to tell you exactly the extent of the issue. I think you are best getting a reputable damp specialist in. They will have a damp meter and they will check the moisture levels in the wall inside and out. It is most likely going to be they who you will need to do the work any way do it will be a worthwhile expense. From the outside pictures I don’t think it is a cill issue. It really does look like the drainage channel is causing the issue.

Yes btw if the drain has been adequately repaired it might fix it but it doesn’t look like it has been fixed yet. Is the wall wet to the touch indoors?

Thank you. The gutter doesn't go around the tv wall which is having similar issue. The tv wall is quite far away from the bit that was leaking in the gutter which has now been fixed as it was a join in the concrete gutter underneath the grate.
The wall is cold to touch but not wet at the moment. Did read high on a damp meter last week.
I'm scared of damp specialists ripping us off. Would use an independent one if they exist.

there is a great deal of water in those walls. the efflorescence suggests it is hard water. Is your tapwater hard? Or are you on chalky soil?

you need to find the source of water and rectify it. It might for example be a leaking drain or pipe. Perhaps a rainwater leak, though IMO less likely. Or are you on sloping ground with water running towards the house?

silicone injections will not repair a leaking pipe or drain. nor will plaster, tanking or other concealment methods.

the water seems to extend over a large stretch of wall. It could do this if there was water in or under the floor. concrete floors can hold a lot of water.

Have you found the dpc?

Yes the tap water is very hard but there isn't any water pipes or kitchen/bathroom that end of the house. The radiator pipes don't go under the floors or in the walls that end either.
There is a toilet waste pipe outside but I would assume that doesn't go under there as that would have to run under the whole garden into the garden behind and through their house. I'd assume it would go the opposite way to the front of the house?
I'm guessing we could be on London Clay. Not sure about chalky soil.
The dpc seems in good condition. Is that impossible with this amount of white walls?
I don't think we are on sloping ground - could the different levels in the garden be the cause?
Not sure how we would rectify that if it was?

I expect the water meter has a stopcock built into it. There may be a T-handle fitted to it that you can screw down to stop the flow. If the handle is missing you may be able to buy one from the water company. The ones I have used are blue and push down onto the spindle, but it will vary with region and age.

Look at the meter. You might have to bale out water and wipe the gauge clean with a rag.

as well as the meter and numbers, you might see a glass window with a turning needle, and an air bubble in it that turns all the time water is flowing. Movement of the air bubble is a much more sensitive indicator than the needle or numbers o the meter. Photograph it if you can, and have a look for your water company's website.

I will explain the ears if and when you can operate the stopcock.

here is an example

This is the water meter. Can I turn that handle on the left or do I need a t handle? I can’t see any air bubbles?

Not sure if image is uploading

it looks like you have a grey handle, though something about it makes me think it will be a quarter-turn valve. if you go on your own water co website they probably have a picture showing how to work it.

the round glass window of the meter, possibly has an air bubble in the middle where there is a circle. again the website (or customer help line) will know how yours works.

what you're looking for is movement of the bubble or needle, even when you think no water should be running. the numbers probably count in cubic metres, which is such a lot of water that they would turn very slowly.

on a rainy day, look at your paving and see if water is running towards the house wall. though if it is beneath the dpc, it should not show above it.

if some of your floors are wooden, take up a board and have a look and a sniff for damp. often the boards under the stairs or under the sink are easiest as they may nt be hidden under carpet or laminate.

can you walk down the garden and take a pic that includes the gutters and downpipes, and the drains they empty into. You probably have gullies just next to the house wall, often near a corner.

Thank you so much. I will take pictures in morning and look at the water website.

I’ve taken some pictures from the back of the garden.
all our floors are concrete through the house so no floorboards to lift up.

Some more

can you turn your house up the right way please

one of the pics shows a downpipe going into the gutter, in an internal corner. one wall looks wet and one wall looks dry. is the dry wall the original house, and the wet wall the extension?

where is the gulley that the rainwater drains into?

I can't see any manhole covers, but some of the paving slabs down the side alley look wet and loose.

are all the floors covered with immovable boards, or can you look at any of them?

on the wet wall, can you take a close-up low down, including both the paving and the dpc, so we can see the dpc and the upper and lower wet bricks.