What construction method does this wall have? (troubleshooting damp)

[dobson156]

Hi,

I am trying to determine what the method of construction is of this exterior facing wall, so I can then figure out what the possible causes of damp on the inside is.

The building is an 1980's extension to a much older stone built detached property. The extension has stone on the front but on the not so visible side and rear is rendered.

At the bottom of the wall for the first 8" or so there is block work, there is a metal lip, and the render starts.

The has perviously been a leaking guttering, which has been leaking for a number of years, I have now rectified this issue. I want to know whether this leaking gutter was the sole cause of damp on this wall. I don't want to replaster and decorate the interior for the damp issues to persist.

What I'd like to know, is from this description can anyone identify what the construction method is and what, if any, damp proofing it should have.

My guess is that above the block work is breeze blocks, sitting on top of a DPC. But that is just a guess.

Here are some pictures of the transition from the blocks to the render, and the guttering before I fixed it.

 

[KenGMac]

dobson156, good evening.

OK, the "Block work" in the images posted is a man made concrete block work.

The horizontal DPC should be at the same level as the "metal lip" [a bell cast render bead]

Where in the property is the damp area you are chasing down??

Yes there is a small missing area of external render + there is a lot of Moss [in the same image] on the man made concrete block?

Sorry no definitive answer, just some questions??

Ken.

 

[dobson156]

Sorry no definitive answer, just some questions??

No, that's very helpful, thanks for your reply.

So presumably the concrete blocks are there for a reason vs using breeze blocks, or is it just an aesthetic thing?

Where in the property is the damp area you are chasing down??

The damage is on the interior side of the same wall. But there seems to be evidence of damp for a 6 meters or so. Roughly 3 meters either side of that guttering - I am not sure whether damage like that could spread out that much?

The damp and timbre survey I got when I bought the property suggested the ground level was too high relative to the DPC - but I also have suspicions about how good the survey is.

Yes there is a small missing area of external render + there is a lot of Moss [in the same image] on the man made concrete block?

You mean in the section at the top of the discolour section (discolouration is from the rusting of the fixing screws for the gutter clips)? Do you think I can get away with patching this section or do I need to strip it back (maybe let it dry out) and then rerender?

Thanks again.

 

[bobasd]

do you have pics of the internal damp?

splash from the gutter is the cause of the green algae and moss - watch the gutter in the rain to be certain the leaks are fixed.
your down pipe should be extended to end just above the gulley grill.
both gullies need stone guards.
why not reach down and clean out the gullies?

is the floor behind the wall solid?
the metal edge to the render is a Bellcast.

i dont see any airbricks venting any internal, suspended floors?
is the wall cavity or solid?

 

[dobson156]

watch the gutter in the rain to be certain the leaks are fixed ... why not reach down and clean out the gullies?

I'll do both of these.

is the floor behind the wall solid?

The interior floor is concrete.

i dont see any airbricks venting any internal

There are none low down below or at the floor level, there is a like a vent/grill on the outside at about knee cap level - it looks like sort of like a boiler exhaust - but there is no boiler or appliance on the inside at that point. The exterior of this vent has been bent up but looks like it should sort of work. Can get this replaces ASAP if needs be. See photo.

is the wall cavity or solid?

This I am not sure about, I was sort of hoping someone with more experience would just be able to tell by looking and the age (1982).

both gullies need stone guards.

This sort of thing:

https://www.screwfix.com/p/floplast-drain-guard-305mm-black/78832

do you have pics of the internal damp?

Picture of plaster / decor damaged behind some stone shelving.

Plaster board a few meters away

Picture of damaged grill/vent at knee cap height.

 

[bobasd]

please, more clearer photos.

hack off the damaged plaster, and look for a DPC in the wall.

could you post pics after pulling the stone shelf out, and removing any skirtings from on that wall - what i'm looking for is any signs of a DPM membrane at the floor/wall abutment.

you appear to have signs of penetrating or rising damp.
the outside brickwork pointing is perished and the bricks/stones dont look too healthy.
perhaps the render is bridging the DPC, and allowing rising damp to bypass the DPC?
you dont need air bricks in for a solid floor.

if it is a 1982 build then its a cavity wall?
but to determine the wall thickness then measure the wall at any convenient opening. 9" wall solid, 11" wall cavity.

the damaged flue terminal need checking by a GASAFE.
photos showing the rendered elevation up to gutter/eaves might help?

 

[dobson156]

Thanks again for your help.

please, more clearer photos.

I will get you those, I should be able to hack off some of the plaster and render and get you those photos this weekend.

the outside brickwork pointing is perished and the bricks/stones dont look too healthy.

The pointing is indeed very soft around the drain. The blocks are cold but won't they dry in time now the leak has been repaired or not?

but to determine the wall thickness then measure the wall at any convenient opening. 9" wall solid, 11" wall cavity.

Ok I've found a gap in the wall. It's 11 inches deep and it does have a cavity.

the damaged flue terminal need checking by a GASAFE.

Out of interest, what do you think this terminal is for? There is no appliance or boiler on the corresponding location in the interior. And yes I'll get someone to look at it.

 

[bobasd]

it might be that the gullies need building up a little around the edges to stop strong water discharge from shooting out?
the Bellcast is rusty - rust expands.

"the blocks are cold" what do you mean?
all the visible pointing probably needs raking out and re-doing.

cavities should prevent mosture penetrating but sometimes cavity insulation bridges the cavity for transmission of damp.
and sometimes the bottom of the cavity is blocked with debris, and that too will bridge any DPC. you would have to remove a few internal bricks to check on the cavity.

remove the flue terminal - fill the hole both sides, and match up the render/plaster as best as possible. no GASAFE needed. or the hole could be used for an extractor, if one is needed?

 

[dobson156]

Thanks for the reply.

Bellcast is rusty - rust expands

Well the render is patchy and discoloured in those areas, so I guess I'll strip that back, in that area, replace the bellcast and re-render. Would I need to leave the block work exposed for it to dry out fully when I take the old render off, or should I be okay just rendering it straight away?

it might be that the gullies need building up a little around the edges to stop strong water discharge from shooting out?

Should that just be done with cement?

"the blocks are cold" what do you mean?

Probably not a lot, haha, the area around that drain all just seem very damp, but then again it does just rain a lot here so that doesn't say a whole lot.

all the visible pointing probably needs raking out and re-doing.

Got it, should this be done ASAP, or am I better waiting until spring?

fill the hole both sides

The other side is covered with a battened plaster board (the picture with the ripped wall paper) so I don't know whether it goes all the way though, do you suspect that was the flue from an old gas fire or something?

I'll probably be replastering that section, so I'll remove that flue when I do.

Do you think once all that's addressed this wall should start to dry out and be damp free?

 

[bobasd]

the galvanised Bellcast will be rusty wherever its installed.
the Bellcast could be left alone until it begins to blow the render.
use a new plastic Bellcast if you do change it.

forget gulley perimeter "walls" just cut holes in the grids and lead the pipes just below the grid so that all discharge is going down the gulley.

point at any time.

probably from an old boiler.

i've no idea. the cause or causes of your damp difficulties is still unknown.

 

[dobson156]

the Bellcast could be left alone until it begins to blow the render.

Ok that's good to know. The area of render around the gutter is pretty discolour and patchy, so I'll probably do that then.

point at any time.

ok great, can I use any mortar for that, or should it be lime?

 

[dobson156]

Right,

So this weekend I managed to hack back the plaster on the interior.

On the right hand side of the pillar, that was behind the now removed stone shelves, the wall has direct plaster onto to the breeze block.

We noted that there is a a vey clear and evident line of salt, after hacking back that plater this line of salt runs along the top of a breeze block, so moisture was probably rising through that block and the getting blocked at the cement and being forced out through the plaster.

The pillar itself holds a joist up, and after hacking back the plaster we expose red engineering brick.

To the left of the pillar is plaster board, held on with dot & dab.

This section is directly behind the guttering and flue shown in the above pictures, all of the bonding to the breeze block on the lower sections had absolutely deteriorated into a sandy mud with no strength. Bit of a shame to remove this as top plaster work was actually very good.

On removal we saw that the breeze blocks were soaking wet, and eventually we got to where the flue on the outside came through the wall. To my horror, the old gas fire had just been removed and the flue pipe was just sticking though the wall with very little really sealing it in, there is a massive gaping hole into the cavity and quite a bit off rubble in the cavity itself. Who ever did this job is an absolute conman.

You can see here the lower bricks are soaking wet, and the two bricks below the pipe are both wet too.

My next steps are to remove the flue pipe, clean out the rubble, try and establish how the is constructed, replace all of the damaged breezeblock. Replace plaster board with batten wall (rather than dot and dab).

Does that sound like, the correct course of action?

 

[bobasd]

i dont see any signs of a DPM or a DPC - the lack of them allows moisture to rise up and present as rising damp in the wall and the floor.
open up the blocks around the hole and clear the cavity.
remove all the D&D and knock off the adhesive snots.
hack off all solid plaster to a height 300mm above the last damp signs.
hack saw the angle beads before attempting to remove pieces.
preumably the brick nib is carrying a lintel bearing?
determine if the Cu microbore gas pipe (?) is safely redundant - where's your cooker point located in the kitchen?

the wall in the pics has return walls at the left and the right - have you examined them for damp?

while you are doing this damp work use the chance to consider any re-arranging of units or appliances or elec or gas outlets etc. but Regs must be followed for all pipe and cable runs.

there are no breeze blocks in your walls - the inner skin looks like Thermolite block, the outer skin seems to be stone or cast stone.

 

[dobson156]

determine if the Cu microbore gas pipe (?) is safely redundant - where's your cooker point located in the kitchen?

The cooker is (unfortunately) electric, for now. This is where an old gas fire was. I have a plumber coming .. whenever they reply to me .. so I'll get them to inspect it then. I'd prefer it if they just took it out. The long term plan is to get a log burner put in, so I don't think there is much need for it now or ever.

preumably the brick nib is carrying a lintel bearing?

Yes

> while you are doing this damp work use the chance to consider any re-arranging of units or appliances or elec or gas outlets etc. but Regs must be followed for all pipe and cable runs.

Yep, I am going to be installing a radiator roughly where that flue pipe is, so will take the opportunity to do that. I am also consider replacing the plasterboard with insulated plasterboard. Although i am not sure how great the benefit would be if it's only one of the 3 walls in the room.

My final question for now is how is how long do I need to wait before constructing the batten wall?

I've done some looking around online and seem it it anything from a few days to 6months!

 

[bobasd]

i asked about the cooker position because it might show where the gas fire supply branched off.

you dont seem to have understood what's been posted - you major concern should be dealing with the cause(s) of damp along that wall.

there's no set time for leaving the surface "open" - its your call.

rendering with a 3:1 sand and lime mix is good practice for Remedial work.