Damp under upstairs window. Porous sill?

[N. Thornton]

I cant think how drilling would tell you whats going on. If theyre not cracked externally I'd leave well alone in most cases.

The interior leaf of Victorian walls is normally rough. Yours looked fairly OK, though I couldnt see it too well in the pic, so I might be wrong. If the wall starts to collapse when exposed then its time to worry. It does happen. If its nothing but a pile of loose rubble, again attention needed. Yours looked serviceable, at least from this distance.

Ideally both, but mostly people just render. Many Vic houses are a bit borderline structurally, so maximising wall strength can matter on some of them. Do use the right mix on Vic bricks, the wrong mix can end up doing more damage.

It would be black. Some tar based paints can just be painted on like any other paint.

only for vague ballparks, gloss tends to have fallen off in 2-3 yrs, pliolite maybe 10 years+. But YMMV significantly.

plaster made from lime :) Most plaster is gypsum based. Lime plastering costs more, but may be easier to diy since you get more time to work on it.

right

yup.

doubtful, penetration is liable to be uneven.

screwfix price about the same too.

Regards, NT

[Phil Addison]

I was thinking of a 1/4" drill just through the plaster to see if it hit render or brick. To see if the whole wall/s is rendered or just the damp bits.

By 'both' you mean repoint + render, or render + plaster? I suppose the former. The right mix is...?

So it'll be pliolite for this job then (or the similar magnolia mentioned earlier).

I like the sound of that. I take it you buy it by the bag ready mixed?

Oh well, I'll try it anyway. If the level doesn't go down it will be encouraging. Will have to shield it from wind and sun though.

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[Phil Addison]

On Sat, 26 Jun 2004 13:01:50 +0100, "stuart noble" >> grease/rubber which can be dislodged by (although not soluble in) water.

That's both of us then.

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[N. Thornton]

That wont really tell you anything about the condition of the wall. It is external rendering that is the caution sign, not internal. And drilling wont tell you anything useful.

repoint and render. For repointing Vic bricks I use 1:1:6, thats cement:hydrated lime:sand by volume. However I'm not going to state that would automatically be correct in your case, it probably is but its upto you to confirm.

I think Anna said Jewsons do it - you can search. I've not used it yet, so cant give you much info there. G'luck.

Regards, NT

[Phil Addison]

OK, I thought you meant internal. I'm not touching the external rendering.

Well, it's only a small area and not supporting anything much. No idea how to confirm that other than asking on here. It goes without saying that any advise given here is taken at ones own risk.

I'll take a look at Anna's posts. Thanks for all the advice.

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[Phil Addison]

After getting thoroughly confused about whether to point and render, with what mix, or to just point then go straight for browning, or bonding, onto the brickwork, I have opted to point and render, so have bought a bag of lime, one of Ordinary Portland Cement, and a couple of bags of sand. I propose to mix 1:1:6 by volume (OPC:Lime:Sand) with no waterproof additive.

I'll use this to point and then go straight on to a render scratch coat, and finish off next day (or maybe the one after) with a skim of Thistle Finish if I can find some, otherwise multi-finish. The standard bags of lime and cement are, I am pretty sure, far more than i need for this 4x2 patch, though it is quite deep in places, up to 1.5".

Does that sound OK? That's tomorrow's plan, so please shout quick if it needs modifying!

Further sill treatment with w/p paint will come later.

I'll update the photos with the result if I'm not too ashamed of it - my plastering is still in the learning phase!

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[Pete C]

Did it absorb any water in the end? Might be worth cleaning it with silicone eater if you need to paint it.

cheers, Pete.

[N. Thornton]

sounds like an excellent set of choices. The only thing I'm uncertain about is what mix would be best for the internal rendering. I've asked people here about it, on ukdiy, so will see what they say. Last time I did something similar I put a thin layer of 1:1:6 on then filled the rest in with 1:1:4. That way the bricks see soft mortar so they dont get admaged later, and you still get a lot of the wall and surface strength of a stronger mix. And I believe the lime content has limited crack healing ability.

BTW the pointing can be done extremely quickly by putting on a glove and just smearing handfuls of mortar along and into the joints. Since its about to be rendered over it doesnt matter a monkeys what it looks like.

Lol, I've got that to look forward to here too :( G'luck.

Regards, NT

[Phil Addison]

Oh well, it's done now with just one coat of 1:1:6. At least I aimed for

1:1:6 but the finished surface looks quite brown so I hope I haven't got too much sand in it. It went on ok though, and stuck ok, so hopefully it is ok.

I made a tool to level it consisting of a long straight batten that reaches the sound wall on either side. To that I nailed a strip of ply protruding 4mm, and length slightly less than the width of the cavity. The idea being that this would scrape the render flat and leave 4mm clear for a plaster skim. That worked out quite well.

I have scratched the surface and left it to go off overnight. How long does it normally take to go off enough to plaster, or should I wait till it is dry (Andrew said to skim after 24hrs but I think that was on a bonding scratch coat) - I suppose it is about the same. Anyway I finished about 8pm tonight so plan to start the skim Friday morning.

One worry I have is that I tested the brickwork to see how much it had dried out, and according to my squawking detector, it hadn't dried out much at all. However my window sill has droplets on it from light rain so I reckon that is reasonably silicone proofed, and I am hoping the squawk from the detector is due to residual salts in the bricks, along with some moisture.

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[Phil Addison]

I'm leaving that test till later and concentrating on finishing the interior work. This is to be a nursery and baby is due in 10 weeks so my daughter is understandably anxious to have it finished. FWIW there are water droplets on the sill after rain so it seems to be proofed so far.

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[N. Thornton]

should be fine in that respect.

Oh, I'd assumed you'd let it dry first. I'm unclear how its going to dry out.

Those compounds get rid of the surface tension, hence the droplet formation, but that does not block the pores. It makes less water soak through rather than none. The thing needs proper waterproofing.

At this point I have some reservations. Maybe someone else will chip in here.

Regards, NT

[Andrew Gabriel]

I use 1:1:6. The render isn't the facing surface indoors anyway (I assume you will skim it afterwards).

Lime acts as a plasticiser and makes the mix easier to handle. I doubt if you are going to get much in the way of tollerance to movement unless you take the cement out. I also use a waterproofer (actually combined waterproofer and plasticiser, so I end up with a lovely creamy/smooth mix to handle).

It's silly to point if you're about to render. The unpointed surface will provide a much better key for the render, and if you are applying the right pressure, the gaps will be filled anyway. Do remember to PVA the brick.

[Jerry Built]

To late now, except for discussion, but why no waterproofer?

If damp penetrates your internal render, you will gey problems with the plaster. Damp and gypsum plasters don't mix!

J.B.

[N. Thornton]

I've done some 1:1:6 rendering now, and I have to agree with you there, its plenty strong enough.

In lime mortar, lime reacts with CO2 to grow a crystal across the crack, and this self healing provides some movement tolerance. I'm not sure if there may still be a bit of this action with a lime cement mix, but the lime can still meet the CO2, as the plaster would crack at the same time, so it seems quite likely, unless perhaps you know about all this in greater depth.

First it depends on the depth of the gaps and how much pressure is applied when rendering. Second it literally takes about 2 minutes to repoint quite a big area with a glove. Its just a way to ensure you get max strength there. It doesnt always matter, often doesnt in fact, but Victorian buildings are sometimes marginal and those ones need any strength they can get. With those ones filling the mortar gaps fully does matter, so I think its worth 2 minutes to avoid a risk.

Regards, NT

[Phil Addison]

Yes, it dried out hard enough (and didn't fall off overnight - hooray!), but the surface had lots of loose sand from the scratches, which I brushed off before skimming. I had a 'test sample' of mix left over and that seems hard enough to do the job though you can dig into it with a screwdriver blade.

Can't wait for it to dry out any more - pregnant daughter needs the room decorated as a nursery. My hope is that the remaining dampness in the wall will dry through the non-waterproofed render and the skim. If it all goes pear-shaped, at least this render is very weak and will hack off easier that the rock hard stuff that was on before.

I hear what you say and intend to apply some Pliolite type paint as belt and braces when I can find my round tuits. However, my understanding is that Solignum works by coating the inside of each pore such that the capillary attraction required for porosity is negated. As I said earlier, their lab told me it is not intended to block the pores, and I suspect that would be impossible to achieve in practice. The evidence of my eyes in seeing perfectly spherical raindrops sitting on the treated sill tells me that those drops are not penetrating it. I'm not saying this is how it works, it's just what they told me, but I am inclined to believe it.

Err.. ?

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[Phil Addison]

Very true, skimmed it today.

To let the damp bricks dry out via it (hopefully!).

I am working on the assumption that I have cured the on-going water penetration and there is a limited quantity of damp left in the 11" wall that needs to breath its way out. I may be wrong, in which case I could be doing it all again next summer :-(

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[Phil Addison]

It was not so much pointing, more just filling the crevices before spreading on the render coat. A couple of the bricks were actually loose so I wanted to stabilise them. Didn't know about the glove trick, but as it was all to be covered I just offered up a blade of muck and shoved it in the gaps with a small trowel. It didn't take any significant time.

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[Phil Addison]

Yes, done now with Thistle Finish.

The bag I got said it wouldn't 'work' unless you used cement as well (as sand presumably), and said it is better still to mix it up as a lime-putty and let it marinade for 24 hrs. Didn't do that, but without digging out the actual words again, I got the impression it had some strengthening effect as well as plasticising - in fact it didn't mention plasticising, though I know from previous use that what you say is right. And yes, it was pretty easy to handle.

Oh dear ,I didn't, is it doomed? :-(

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[N. Thornton]

not at all. Brushing the wall with water is another way to do it: yours is already wet.

Regards, NT

[N. Thornton]

Lets just hope your idea's right. :)

Regards, NT