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

[KenGMac]

dobson156, good evening, again.

Suggest you consider getting a De-Humidifier + fan

Check out cost of a weekly hire of a "decent" De-hum + a "big" fan

Caution! the Thermalite blocks will dry out faster than breeze and a load faster than brick or masonry.

The above will dry out the walls far faster than just waiting and opening a window or two when it is dry outside??

Ken

 

[dobson156]

Thanks for the reply.

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.

Oh no, I get that completely.

I think the cause was the flue pipe bodge job and the guttering. I've fixed the guttering and I am taking the flue out and replacing the brick work around it tomorrow.

I can't see anything obviously wrong in the vacinity. When I take the bricks out tomorrow, I'll of course be able to give the cavity a much better inspection.

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

So that'd contain no cement?

 

[dobson156]

dobson156, good evening, again.

Suggest you consider getting a De-Humidifier + fan

Good evening! Yep I've got a relatively small dehumidier on it now, I'll try and get a bigger one.

And good point out the fan, I've got a fairly powerful one I could uses.

Caution! the Thermalite blocks will dry out faster than breeze and a load faster than brick or masonry.

Good point.

The above will dry out the walls far faster than just waiting and opening a window or two when it is dry outside??

When is it ever dry outside?

 

[KenGMac]

dobson156, good evening, again.

Fans are the key to passing as much air past a damp surface to encourage the moisture trapped to be drawn out.

In an insurance claims situation the fans used are [best described as ] industrial about 750.mm when circular ones employed and a wee bit noisy !

Beg borrow and place fans firing them at the wall, and indeed towards the flue??

Ken.

 

[dobson156]

Ok, wall opened up.

And wow, so much debris bridging the cavity.

I can definitely confirm that both the outer wall has a DPC (a black layer which I can see for the exterior, and the interior wall is built onto of the concrete slab which has it's own transparent plastic layer which then "folds over" and that's what the interior wall is built on top of.

There was a slight "lip" where the interior wall is inset on the slab, and debris has got trapped on there above the DPC.

I have remove all of the bridging debris and some of the debris below the level of the concrete slab but access is incredibly tight and awkward I tried to suck as much I as could up with henry.

I think that's going to "have to do" - all the remaining debris is below the DPC and there is SO much less than both and the stuff I pulled out was soaking wet so I am confident that it was part and parcel of the problem.

I have drawn a picture or where I am at now.

• Orange is interior wall
• Blue is exterior wall
• Blue dots are DPM
• Red is the debris I really can remove
• Green is all the debris I have removed.
• You can see the sight lip that is formed by the concrete slab and the interior wall that all of the larger green debris was getting trapped on.

 

[KenGMac]

dobson156.

If you can leave the opening in the internal wall open for as long as possible, depends on your time scales for using the room.

To assist dry out of the internal areas of the cavity wall [within the cavity] suggest you get a fan to blow air into the cavity.

In insurance claims for failed retro filled cavity insulation, once the failed insulation is removed forced air is fed into the cavity, thispeeds up drying immensely.

Ken.

 

[dobson156]

Noted.

I don't really NEED the room for a few more weeks - but the room does contain contents which can not easily be removed so I am weary about turning a fan on too high and blowing dust everywhere.

That said on a lower setting + fan heater + dehumidifier is very doable. I might be able to tend the opening and then can run the fan at a higher speed.

Thanks for you input!

 

[bobasd]

take pics of the opening you have created in the inner wall.
and take pics inside the cavity in various directions, including above - use a light.
photo the DPC on the outer skin.
and a standing back pic of that whole kitchen wall
you can buy from, say s/f an inspection mirror - they come with various length handle's and adjustable mirror heads.

there's no signs of any DPM peeping out in the wall and floor abutment pics?

 

[dobson156]

take pics of the opening you have created in the inner wall.

After A LOT of cleaning

and take pics inside the cavity in various directions, including above - use a light.

Best I could do.

Straight down

To the right

To the left (you can just about make out that void, below the lip, get a lot deeper here).

photo the DPC on the outer skin.

This is a pic of the black DPM from the exterior wall as view from inside the cavity. It is higher than than the DPM of the interior wall - by about 2/3s of concrete block.

 

[bobasd]

thanks for the prompt pics.

it will pay you to open similar access holes along the wall so that you can deal with all the cavity debris and the bridging snots the length of the wall.
i can see the crumpled up membrane material in one area directly below but not in another on the right hand side?
anywhere the membrane is touching the outside skin then its bridging damp across the cavity - only wall ties should cross the cavity.
membrane dangling down in the cavity could be wicking up moisture - that moisture could present as rising damp.

on the outside skin i can see the DPC - where does that DPC show in any pic of the outside face of that wall. can you point out the bed?

like your inner skin, the outside skin has been built with thermalite blocks - for me, this is wrong because these blocks shouldn't be used as an outside skin neither should they be rendered over on the outside. they are for inside work.

 

[dobson156]

thanks for the prompt pics.

No problem, I really appreciate your help with this.

it will pay you to open similar access holes along the wall so that you can deal with all the cavity debris and the bridging snots the length of the wall.

Does it only matter if they're above the DPC? As I said, I am really going to struggle to get any access even with a vacuum below slab.

I think it'd take a month of sundays to do that for the whole room? I think that big lump you can see in the left facing pic is concrete on a wall tie - I can probably reach in and clean that up.

i can see the crumpled up membrane material in one area directly below but not in another on the right hand side?

The crumpled up bit I think is a join between two sheets, and they've folded the end of one over.

The pic to the right that is only just out of frame, and you can see it's much neater and more orderly. I am going to get some DPM tape and tuck the crumple away neatly to reduce the the chance of bridging and any future debris getting caught on it.

on the outside skin i can see the DPC - where does that DPC show in any pic of the outside face of that wall. can you point out the bed?

If I refer back to this photo, then the DPC is on the top of the 2nd exposed brick - exactly where it meets the bell cast render bead. It's quite hard to photograph but I can try in the morning when the sun is up.

like your inner skin, the outside skin has been built with thermalite blocks - for me, this is wrong because these blocks shouldn't be used as an outside skin neither should they be rendered over on the outside. they are for inside work.

Damn, not much I can do about that :/

I've got solid concrete blocks for the repair of the exterior wall. I'll make sure I keep on top of the render - best I think I can do.

Anyway, thanks again, you've been a big help!

 

[bobasd]

the outside ground level is much higher than the inside FFL - you will have to clean out the full length of the cavity or the whole damp process will begin again.
look at a pic of a flat bar - make yourself something with that kind of hook on the end and securely attach it to a pole or stick.
where's the pics for looking up?
you dont have to empty the whole depth of the cavity just the rubble thats affecting the inner skin or bridging snots.

 

[dobson156]

Hi again.

> the outside ground level is much higher than the inside FFL

I took some measurements, the top of the internal concrete floor (and top of the DPM) is 2" (50mm) higher than external ground level. The DPM on the external wall is 7" (170-180mm) above the ground level.

I drew a diagram.

where's the pics for looking up?

voila

I looked around, there is no bridging other than the wall ties.

 

[bobasd]

OK, thats great - i must have misunderstood your earlier posts/pics.

i noticed your continuation post on the Plastering forum - its better to keep all your posts on same subject on the same page.

 

[dobson156]

OK, thats great - i must have misunderstood your earlier posts/pics.

So you reckon I can get this cavity as clean as I can, so any crap is below the DPM and we're good to seal it back up?

i noticed your continuation post on the Plastering forum - its better to keep all your posts on same subject on the same page.

Oh sorry, wasn't trying to game the system or anything, I just didn't want to distract from this post - but wanted to start preparing and getting the materials for the end of the job!