Damp wall after extension built - Looking for advice on drainage etc

[seanandruby]

What about ventilation, is there any, are there any air bricks?

[anymach23]

Old part of the house has double glazing.

This room with the damp now opens out into a sunroom with double doors.

Previously it had a solid wall with a large window with a radiator below. With the sunroom, now this area would be more ventialted than before.

There are no air bricks in operation now as the floor is now solid. It was suspended joists before.

I'll post up some more photos later.

Thanks for all the input so far. Loads to think about.

Cheers, Andy

[Mikey_C]

if the wall has ever had a damp problem before (since 1927) the salts left in the wall/plaster will "attract" the water from the works you have had done (concrete, screed, plaster, tile adhesive etc.) as normal salt would if left out in a "damp" environment.

was a specialist plaster used on the that wall or just standard? you could try also a dehumidifier to try and remove some of the moisture from the air, produced by the building works.

[anymach23]

No specialist plaster used. Just bog standard. The building work was completed last January so I suppose that there has been a fair amount of drying time.

Now that there is the possibility of the damp not rising, I'm going to take some measurements from the outside and mark the wall on the inside exactly where the new cavity wall butts up against it. The general problem area is wetter in some parts than in others so I'll maybe be able to spot a pattern.

Cheers, Andy

[digerjones]

fibre board between walls? i would say that is not right, sponge?

have you checked this area

[anymach23]

Ok, here's the latest installment.

I did some more investigating yesterday. I moved a unit at the other side of my fireplace and could see that the damp is pretty bad on that side as well. The vertical chalk lines show where the chimney breast is on the outside.

https://picasaweb.google.com/lh....ectlink

I took the skirting boards off and found the plaster to be very damp at floor level and there is evidence of mould.

https://picasaweb.google.com/lh....ectlink

Seeing the overall pattern makes me think that is more to do with the fireplace area. And maybe there is seconday dampness towards the corner where the new extension starts?

I looked at some old photos of the building work and in this photo I can see a copper pipe coming out from below the old fire. Maybe there is some sort of back boiler in there?

There also appears to be no brick footing beneath the fireplace. Could this be open to the outside ground?

https://picasaweb.google.com/lh....ectlink

Close up beneath fireplace....
https://picasaweb.google.com/lh....ectlink


This photo shows the DPM in place before the concrete subfloor was poured. Maybe the damp is getting in below the fireplace and working up the back of the DPM turn up, and into the new plaster?

It's worth noting that this photo shows evidence of some damp in the wall adjacent to the fireplace, before the concrete was poured.

https://picasaweb.google.com/lh....ectlink

When the old suspended floor was in place there would obviously have been more ventilation here which could have been helping to keep everthing drier.

Moving outside, this photo shows the chimney breast. You can see the word 'floor' written in chalk, low down where the bricks start to get damp looking, indicating inside floor level. Ignore marks above as these were a mistake. The crazy paving came up to this mark.

https://picasaweb.google.com/lh....ectlink

https://picasaweb.google.com/lh....ectlink

The white line of salts on the exterior wall was noticed after the plastering was done and I was thinking that it roughly followed the line where the plaster inside the house taken right back to the brick and 2 layers of plaster added. These areas took ages to dry. The rest of the walls were just skimmed and dried pretty quickly. Just looking at it now, I see that the line of salts is on the ouside of the chimney breast as well. Not sure if that is significant.

There was some repointing done in this area as we had some damp in the front room of the house, also near the chimney breast area. The builder continued the pointing on to include this rear chimney breast. Not sure if the pointing used lime mortar like the original. It looks darker than ordinary mortar.

When I started investigating this 4 months or so ago, I removed the original crazy paving just leaving the quarry dust, that was dug back from the wall. |The crazy paving butted up to the wall about inner floor level. The rubble that is there now was only put there a week or so ago and I haven't got round to clearing it.

Sorry for the length of this, but thought it would be better to give a full picture of what is happening.

Cheers, Andy

[lutonlagerlout]

well 2 things there andy

you have gone from a ventilated timber floor to a solid concrete floor, have you blocked any ventilation to other parts of the house?
also concrete requires a lot of water,as the concrete cures that water must evaporate,where does it go
when we concrete or screed floors inside a house the condensation is phenomenal
screed alone takes 1 week per 10mm of screed to dry out and that is laid quite dry

is the fireplace still vented I.E. is the chimney still open at the top?
it is important for chimney flues to be vented as closed voids are a magnet for dampness

also if you are having a fire you need a 225 by 225 hit and miss vent in that room, gas safe or HETAS engineer will tell you the exact requirement

cheers LLL

[anymach23]

Hi LLL

That's a good call on the concrete drying. That would tie in with the amount of damp in this room.

The only thing conflicting with that theory is that there is no damp like this in the rest of the house. We had the complete groundfloor done. The front room that also faces this outside wall is pretty much ok.

I have a c-cap fitted to the chimney which is designed to vent disused chimney's plus an air brick up near the stack for each flue and a lower level one about chest height outside.

No ventialtion has been blocked off to the rest of the house.

The concrete subfloor was poured in early september 2009. Could the concrete still be drying after all that time?

If its coming from below is there anything I can do except for giving it time to dry out?

Over the next couple of days, I hopefully get a chance to do some investiagion outside in the Chimney breast area.

Cheers, Andy

[henpecked]

Over the next couple of days, I hopefully get a chance to do some investiagion outside in the Chimney breast area.

I know what my monies going on

[lutonlagerlout]

the chimneys seem a focal point for the damp
are there underground vents going to the chimneys?
are the chimneys properly weatherproofed?
try a smoke test and see if they draw
also with the alley way all dug up and rain will get to the lowest point
if the alley was paved water could be drained away from your walls
LLL