Soil in Mortar Joints

[oursurveysaid]

My old 1880s victorian terrace has the usual rear addition kitchen with bathroom above. The London stock bricks have been painted about halfway up the wall by previous owners. They used a non-breathable paint, so the solid walls are cold and damp. Plaster work inside has blown and the kitchen cupboards stink.

Having removed some of the paint, I've uncovered empty mortar joints everywhere and bricks with no faces left which look pretty porous. There are quite a lot of woodlice and even a few worms and millipede-looking things living in the walls, and it seems they have carried soil in between the bricks, replacing whatever mortar was used originally.

I'm planning on having a side return extension next summer, but would still like to fix the wall in the meantime in case I don't end up extending, and to solve the damp issue.

From what I've learnt so far, I need to remove the paint and repoint it in lime mortar. I've had moderate success with PeelAway 7 from the test kit, so would people recommend using that, followed by a wire brush attachment on a drill? Are the porous bricks likely to be a problem, or do they not matter?

Regarding the correct mortar to use, would 6:1:1 or 5:1:1 be better than a 3:1 lime mortar? I've read conflicting opinions and would like to hear a few more! I'm keen to repoint it myself, but does the soil between the bricks pose a more serious problem? Should I rake it out a brick at a time and repoint? I'm assuming I shouldn't do much in one go as the wall might fall down.

Look forward to hearing your ideas.
Joe

 

[Newboy]

1. What ever you be, be gentle!
2. Don't use wire brushes - far to harsh and will damaged the brick faces. Don't try high pressure water or grit/sand/bead blasting either.
3. I'd be inclined to give the masonry some time to dry out
3. Rake out to around twice the depth of the mortar bed
4. Point using lime mortar

All that said, the condition of the bricks may be so bad that the exposed faces may be damaged beyond repair

 

[roboughton]

All that said, the condition of the bricks may be so bad that the exposed faces may be damaged beyond repair

Looking at them it maybe better to look at having it rendered over to save you a lot of time, especially if you are having and extension where they would become internal and covered by plaster anyway.

my 2pence worth.

 

[theprinceofdarkness]

The earth is not adding any strength and will hold the water as mud. As said, its best to try and get as much out dry. I use a 6mm striking iron and a variety of home made tools based on stainless steel table knives. A thin long bristled brush would be extremely useful. I bought 10 polypropolene ones from Carrefour in Calais some years ago. when you are about to point use a pump garden spray to wash the remainder out and dampen the bricks. Start at top right and work along towards the left.
As for the mix, only use sharp sand. I have used 1:1:3 on a Victorian garden wall and 30 years later it has not changed at all except it has all evaporated from in between the top course of decorative bricks where the joints face upwards. On my rock and rubble cottage, I use 1:2 1/2 NHL 5 lime and it seems to remain wet all year round, so am not going to recccomend it.
You will need a dot board or "hawk", again I made my own as the full size one I find too large, but as my rock'n rubble pointing is extremely irregular, it takes about 3 or 4 times longer to do. Take some time with your lash up of tools and mortar bucket, you will be using them for a long time so make it easy for your self. Such as stand on a high stool and hang the mortar from a hook on your ladder.
Frank

 

[^woody^]

Jet wash it, rake out the joints repoint.

3:1 lime or 4:1 cement, never use cement in a lime mix. One or the other.

 

[theprinceofdarkness]

Woody, for a cement mix you use Hydrated lime, this is not the same as the lime you use for lime mortar.
Frank

 

[^woody^]

Woody, for a cement mix you use Hydrated lime, this is not the same as the lime you use for lime mortar.
Frank

Yes that's OK as a plasticiser in a cement mix, might be useful as a plasticiser in a cement pointing mix, but if the OP has lime mortar and needs a lime mix then he should not be using any cement in it at all.

A lime mortar should use hydraulic lime (aka slaked lime) and not the hydrated lime in bags from the merchants

 

[vinn]

joehood, you are wasting your time and money attempting any kind of temporary, almost cosmetic, repairs. The re-pointing and paint removal will work to a degree but the brickwork will again become sodden and moisture will still enter into the kitchen interior surfaces and units.

 

[oursurveysaid]

Thanks folks. I think I'll look for all the problem areas where there's no mortar and patch up with a lime mortar as suggested.
The extension involves knocking down all of the problem walls, so all will be fine when I get around to having that done.

 

[vinn]

joehood, Why? What for? How do you imagine that patch pointing is going to help you forward?


I'd suggest that all the painted/rendered brickwork is a problem area.
To possibly gain a little time you could hack off all the render/paintwork including the plinth at the base of the wall and any returns above the concrete step and the other outside corner.
Rake out to 22mm and point up with L&S or S&C.

The steps might be bridging any DPC and allowing moisture to endanger your suspended floor/joists.

 

[oursurveysaid]

Just to stop it from getting any worse, in case my circumstances change regarding the extension.

The steps don't come up as far as the DPC. The slate is in line with (or even slightly above) the kitchen floor level, which is solid concrete, so no joists to worry about.

The upper half of the wall is still bare brick, and is warm and dry. No damp patches upstairs. It's only downstairs that's a problem, where it's painted over and much colder to the touch.

 

[vinn]

I wont go on but your reply doesn't make that much practical sense? Pointing wont stop moisture penetration, and at some future stage you will have to almost, at the least, re-build the walls in question.
Why, presumably a previous owner scheduled a solid floor with the walls in that state ( & probably the cause of a need for a concrete floor) to be installed before doing any remedial work on the walls is ...?
So, is that dark line in the bed two courses above the step the slate DPC?
Given that your kitchen FFL is perhaps about 600mm above ground level there's quite a bit of backfill hardcore. Hopefully you have an installed membrane( a DPM)?