Is this damp in external wall?

[seasider]

Hi, we have this external wall and the mortar is discolouring and becoming slightly flakey (more so in the bottom right of the picture). It is a Victorian terraced but the previous owners rebuilt this wall (some reason used smaller bricks and massive mortar joints). Anyway, we want to render the wall but want to address this issue first. Internally there are kitchen units and a plastic damp membrane so no issues with damp inside. But not sure what trade we need in (we rang a damp company we’ve used before but they say they only deal internally). Is it a builder? And do you know the remedy so we sort of know what to ask about to get them to come round for a quote.

I can’t see a DPC or any DPI holes. If needs a DPC can these bit fitted retrospectively? I wondered if it could be the drain leaking but the older bricks and mortar round the corner look fine. There are no air bricks on this length of wall too, but there are 3 that run along the other kitchen wall (the corner with the 3rd pic)

Cheers
John

 

[^woody^]

Problem may be with the pointing. The joints are too big and as the face is shot, they absorb and retain rainwater.

Repoint

 

[seasider]

If we were getting it rendered, would it need pointing?

 

[tell80]

No, no pointing for rendering is needed. The "flaky mortar could be raked out & re-pointed.

From the evidence of the pics you appear to be complaining about some minor efflorescence in the newish brickwork, & a damp discoloring - given you have cavity walls I doubt that its anything but an unsightly problem.
Do you know if you have plastic DPC in either wall?
Cavity debris can bridge any DPC - to examine a cavity you will have to remove some external bricks.

During dry weather it can be dry brushed off.

The lack of air bricks is a concern if you have suspended floors?

Historic Injection holes can be seen on the old brickwork - indicating there was an historic damp problem.
You need to pic & post the interior walls esp at the tanking and skirting.
Do you have CWI?

Pic and post the gulley with the cover off - where does that gulley drain to?

 

[^woody^]

If we were getting it rendered, would it need pointing?

Sort of.

You should not render onto soft sandy mortar, as this will fail and be prone to the same high water absorption - leading to pattern staining through the render.

Still rake out 25mm and gob it up with better mortar or part of the render scratch coat.

If you are going to render, then for completeness, you may as well remove a couple of bricks to investigate the cavity.

 

[seasider]

Hi @tell80 , thanks for the reply. Our main concern was getting it rendered but it being compromised so wasting money.

I can’t see evidence of a DPC. There is an airbrick round the corner but I think this part of the kitchen is solid floor (an old extension long before we moved in - like an out house knocked through). Further along it is suspended floor and more air bricks.

The gully should lead round the corner and connect with the other pipe work. I know we had a gully at the front and the clay pipe collar was cracked. So I could dig and look (but the old bricks look ok the other side of the gully except a patch of efflorescence further along ).

There is no CWI that I know of. The inside has all kitchen units where the wall looks worse so hard to get a pic. One pic is under the plinth towards the gully. The other is a bit of wall space, but no evidence of damp there.

I’ve rung a couple local builders so hoping they’ll come and have a look,

thanks for the advice

 

[seasider]

Cheers for the advice @^woody^ .

As well as a couple builders, I’ve asked some renderers to look so hopefully amongst them I’ll get it sorted. Thanks for the advice

 

[^woody^]

Under the units, up the wall looks like a membrane from a wall tanking system

 

[seasider]

Under the units, up the wall looks like a membrane from a wall tanking system

Yeah when we bought it and done up initially back in 2007, we had damp work done in kitchen, with membrane internally and a DPI externally. The latter never got done as builder went out of business.

 

[tell80]

Definitely dont do any rendering, for one you still dont know the cause or causes of the damp, & by rendering you might be making things worse (at further expense).

The under unit pic shows the wall Tanking that you mentioned in your opening post,
If the solid floor is Victorian then typically no floor membrane would have been used.
So the internal damp that was treated with tanking could be associated with the lack of a floor DPM? And/or, as previously mentioned: a blocked cavity?