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Decomposing Mortar?

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stillscottish

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We built the house 24 years ago and due to planning laws at the time, couldn't build up to the fence line (althougth there's nothing there, just parkland) so we had to have a single garage and I built an (illegal) car port later on the side of it. Carport area was paved with a sheeted roof with a roller door at one end and the other opening on to a fully enclosed patio area.

About 18 months ago, as planning laws have changed, we extended the house roof over the old carport area with a brick and glass brick wall down the side and a properly laid slab. Since then the mortar in the old wall seems to be decomposing; see photos.
The old carport area was weathertight and I didn't notice this in the past.

At the moment I have to vacuum the wall every few weeks.

Any builders out there want to offer a suggestion?

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browndog

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That is a bugger Campbell, I can't think of anything that will stabilise the mortar except possibly a stiff mix of bondcrete to bing the loose stuff up. The only other option I can think of is tuckpointing.

cheers

Browndog
 

raven19

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As per DS's post, what is behind this wall? Source of moisture? Rising salt damp?

Can't replace the mortar without ripping down the wall, so maybe render the wall? (But you would want to find the source of this issue first).
 

bradsbrew

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Is it the mortar breaking down or is it effloresence ( white powder)? Depending on the what is behind the wall, is it brick veneer , cavity is one side exposed to moisture etc. If it is just the mortar breaking down give the wall a wash with diluted hydrochloric acid ( be careful I have seen the results of a bricky getting it in one of his eyes, he is know refered to as the one eyed brickie) as this will both clean the degraded mortar and make the surface porous, then when dry it needs to be sealed, you could go with browndogs idea of the bondcrete wash or use a oil such as solpar oil or a product like acraglaze which is a waterborne clear coat for masonry surfaces or you could go hardcore with a non sacrificial two pack urethane normally used in anti graffitti systems. Do a test brick first with the coating you choose as some will leave a sheen on the surface.

Cheers
 

RdeVjun

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I don't want to sound too negative Campbell and I'm certainly no builder, but that could well be a urban salinity or rising damp issue. If that's the case then I'm afraid the prognosis is not pretty... :( If it is, I'd look first at ensuring adequate drainage in the soil surrounding the slab and wall, that would address the actual root cause.
 

stillscottish

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It's the garage wall. The old mortar looks noticably "sandier" than that in the new wall but there's no noticeable damp in the garage and there never has been. The dampcourse appears to be intact and wasn't bridged by the new slab. As I said, it only started happening after the new build.


The way it was

old_bar.jpg



During the build

DSC_0401.jpg

DSC_0001.JPG



Finished

DSC_0007.JPG
 

Ducatiboy stu

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Usually it is from moister that brings up salts with it. Its the salts that do the damage. Adding the new brickwork may be affecting airflow etc, also it could have been dodgy in the first place. Mortar is supposed to be sacraficial, ie it breaks down before the bricks do., basically all you can do is to chip out the old stuff and re mortar it
 

komodo

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Not a brickie but I have seen similar in the past and was told that its due to the motar which has mostly remained slightly moist completely drying out - ie normally when its exposed it gets moisture which keeps it all bound together but then when you extend it allows it to properly dry out and become brittle and break down.
Not sure if its a sign that things we're right in the past or what I didn't really go into it too much when I saw it and the bloke whos place it was didnt seem to concerned he was just going to get it re-pointed. Not someone I see very often these days so I cant really even ask him for you.
His was pretty much the same though a "lean to" had been built along the side of the garage and then they extended the house into the existing garage and then added some bedrooms the other side. He seemed to indicate the ducted heating affected it?
This was a few years ago now though.
 

spog

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moisture,moisture,moisture,that IS your trouble
moisture/water/vapour is one of ......The main probs with housing.
check that drainage is not being blocked/hindered in anyway.
as a side note it could also be that the brick mortar is not up too standard,if you can push say a piece of wire through it,or rake the mortar out with a stick or such,that will tell you that the job is sub standard,IF you have an odour problem as well,...musty/mouldy then that pionts to a ventalion issue....
i mean no offense,but i see this type of problem so often .been in the building trade 30 + yrs,and will always see it raise its ugly head.....cheers.......spog.........
 

RdeVjun

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There's a few efflorescences on your old brick paving by the looks, so water has been evaporating where there is now a concrete slab. Then the local hydrology changed when permeable brick paving replaced impermeable concrete, now there's only one way out- up that wall and it is acting as a big wick with the smallest breach in the damp course enough for water to flow through.
Its a bummer mate, to start with I'd look at a trench around the slab to intersect any subsurface moisture, see if that has any effect, if so make it permanent.
 

Dave70

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Just taking a guess looking at the photo (2nd from the top), but is that a bathroom / laundry behind the wall?
 

stillscottish

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Garage behind the wall.

There's no efflorescence on the brickwork neither is there any musty/damp smell the other side of the wall in the garage.

I'm inclined to agree with Komodo. Although the old sheet roof was sound, the side was just insect screen which would have let ambient humidity in. There's now a solid wall there plus I would agree that the old mortar is definitely a bit suss, very sandy.
I think it's a job for Bondcrete and a paintbrush.


Cheers

Campbell
 

Goofinder

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http://www.heritage.nsw.gov.au/docs/HVC014...uide_FA_web.pdf

Don't just render over it or replace with harder mortar - that may only make things worse as the bricks may start decaying instead. Work out if there is excess moisture and evaporation causing issues.

I noticed a bit on my house and eventually worked out that when it rained water was draining from a fair way away but ending up next to the house due to unevenness in the pavers which had settled over time. Luckily it is only below the damp course but still I've put in new drainage which has stopped the water flowing there. Now to wait for it to dry out a bit more then rake out the old mortar and replace with new (still softer stuff as I still want it to be sacrificial in case of further issues).
 

browndog

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Garage behind the wall.

There's no efflorescence on the brickwork neither is there any musty/damp smell the other side of the wall in the garage.

I'm inclined to agree with Komodo. Although the old sheet roof was sound, the side was just insect screen which would have let ambient humidity in. There's now a solid wall there plus I would agree that the old mortar is definitely a bit suss, very sandy.
I think it's a job for Bondcrete and a paintbrush.


Cheers

Campbell
Maybe the bricks were laid by a tightarse scottish brickie who was stingy on the cement hey Campbell :D

-BD
 

staggalee

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I thought you were going to burn the boat and trailer, the way you had all those tree branches piled up around it last week :lol:
 

browndog

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I thought you were going to burn the boat and trailer, the way you had all those tree branches piled up around it last week :lol:
Are you talking about my blue and white one Staggalee?
 

staggalee

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Are you talking about my blue and white one Staggalee?
I didn`t note the colour, just the fact that some sort of ancient Viking sacrificial act was in preparation.
What size motor was yours?
 

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