Damp under upstairs window. Porous sill?

[Meoww]

It sounds like you're on the right track if you've sealed the cill. The chances of it being porous are quite remote and if it is, you could probably cure this with a water repellant.

It's difficult to envisage exactly what you've got but if you've removed the plasterwork from the inside, you should be able to see if there's a dpc there or not. However, if you can't see it, it could be quite a major job to put one in and you're probably better going along the sealing it all route.

Make sure water can't blow in from underneath and from the sides and that's about all you can do. I presume you're making good these seals with mastic?

From your description of where the wall is wet it certainly looks like the culprit is the cill and not the wall.

Just don't re-plaster internally with a waterproof mix. Browning and skim will do quite nicely for inside. If you haven't cured the problem at least you'll be able to see its manifestations and not run the risk of wet/dry rot further down! You may get effloresence until it all dries out but wiping this off is easy and it'll stop when the brickwork is dry.

Don't suppose you can post a photograph?

Cheers

Patrick

[Phil Addison]

Thanks Andrew for clearing that up. I haven't been able to get up there on a ladder yet to have a closer look, but last time the sill material looked pretty recent.

If it IS rendered like yours!

I understand why you can't use these if it is permanently damp, but do you mean you can't use them if there is still residual damp that is expected to dry out through the plaster. In other words must it be completely dry before using plaster as scratch coat?

Is that why cement render often seem to be used after damp treatment, so that it can be applied straightaway to the still wet brickwork?

Are you saying if it is not totally dry I should use that sand and cement mix rather than bonding plaster as the scratch coat? What is the problem if it is too wet; won't stick I suppose?

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[Phil Addison]

Ahh, yes. See what you mean.

That would make it prime candidate then - cheap, easy to apply and durable then. Is your preference for body filler because of its better adhesion to the sill? I must say I would not relish working with the latter if an easier alternative would do the job.

Thanks, found Pliolite here

> By 'any solvent based paint' is that as in ordinary gloss

The adjacent walls are rendered in a yellowish spar, so a light colour would be OK. Think I prefer the idea of a specialist paint for longer life though.

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[Ian Middleton]

[Pete C]

Hi,

Probably best to put it on with a spreader and brush it out. Have a look for epoxy concrete or driveway sealers for some examples. If it's a concrete sealer it will need to have UV inhibitors.

Also it's better to seal around the window after the cill has been sealed, most sealants stick better to a non porous surface, and if the sealant starts to come away there's less chance of water getting into the cill.

cheers, Pete.

[Andrew Gabriel]

So does mine;-)

OK, or cracks in the casting;-)

The problem is if it takes weeks to dry out, as it well might. That's long enough to damage the plaster. You end up with the finish coat looking permanently dark (like it was wet), and the rear turns to powder. You'll probably also get white powder salts growing on the surface as the water carries salts to the surface and evaporates leaving them behind (looks like white mold), but that just brushes off. If the wall is decorated, it doesn't come off so easily, and left in the decorations, I've heard it said it can have a hygroscopic effect, keeping the area slightly damp.

More likely is that because damp treatment usually doesn't work because it's wrongly diagnosed, you have to make the finish waterproof to hide the damp. Most damp treatment companies seem to only have equipment for injecting a damp proof course, so the only thing they're likely to diagnose is rising damp, which mostly isn't the cause. The sand and cement render will project against damp wall (unless it's soaking wet), without injecting it.

Another factor may be to prevent the plaster bridging the new injected damp course. Sand and cement should be OK for this (as always, assuming it has waterproofer added). It may not be possible to inject low enough to avoid bridging by internal finishes due to outside conditions.

I haven't tried when its very wet, but that might be an issue. The suction might be non-existant, and the PVA coat might not soak in to the brickwork (could dilute it less perhaps and hope it mixes with the moisture at the surface).

[Phil Addison]

Not sure about 'sealed', but I hope so. I sprayed them twice with stuff sold for treating penetration problems in walls. Can't recall the name at the moment.

Can't see it so far.

That is possible. I didn't put a bead under the sill or at the vertical edge. Perhaps that would be a good idea. I used Unibond silicone from B&Q, about £7 a tube.

I like the 'when' :-)

Hi everyone. Hope these photos are useful. I took them yesterday.

This is the inside wall

these are some shots of the sill taken with camera poked through the upper opener, and through the glass can see the wall construction is a bit odd (in the tall edge-on photo). The top 3 courses are not flush with the rest and protrude about

1/2" into the room. The 4th course from the top protrudes about 1/4". That, and the different colour of the top 3 courses makes me suspect the original sash went lower that the recent uPVC frame. The darker brick at the top are also the dampest, but I think they might be getting slightly drier now they have been exposed a few days. Heavy rain tonight should be interesting but I don't expect to be able to get round there again before the weekend.

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[Phil Addison]

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[Phil Addison]

Hmmm... I've just realised that everyone seems to be assuming that the sill is still porous. Don't forget I have given a very generous sloshing with silicone fluid. I WAS hoping you'd all say that should be OK, but the only comment on is from Andy saying his only helped a bit. Is it the case you all think that stuff was a waste of time?

Pete, I did put the new silicone bead seal around AFTER treating the sill. Guess it will have to come off again if I DO need to paint/spread/skim with some other stuff as well.

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[Phil Addison]

;-)

I meant I'm not convinced it is that construction, but I haven't had a chance to test it further for brick innards.

Oh aren't we cynics here :-). My daughter had two quotes from builders before I got volunteered to look at it. First guy said to hack off the plaster, and render it with sand/cement. He didn't notice apparently that it was already done and the plaster skim so thin in places you could actually eyeball the cement!! Second guy was sure it just needed silicone fluid treatment outside.

True. I suppose there are some outside conditions that can't be rectified, but on here we would rectify them and not need the injection.

I see. I'm now thinking of leaving it open for a few weeks or till its obviously drying before doing more.

Thanks again everyone for such excellent details.

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[stuart noble]

Body filler is also cheap if you get it from a car paint trade outlet. Around a tenner for 3.5 kgs IIRC. It does have better adhesion and has the advantage of being waterproof without being tacky. However it is a bitch to use in this sort of situation. I find loads of hardboard scraps useful. Use them as a base for mixing and as an applicator, and chuck them for each mix. Only mix what you can apply in, say, 2 minutes (which isn't a lot for detailed work). A basic resin without filler (fibreglass resin) is very easy to use and has the same benefits.

Johnstones had Magnolia on special offer recently ("Stormguard"), which made it virtually the same price as standard masonry paint. As an aside, it occurs to me that those cheap paving slabs are "concrete", yet water goes straight through them.

[stuart noble]

'Fraid so. These products are usually siloxanes which, unlike silicone, don't form a continuous film. They cure as microscopic pellets of grease/rubber which can be dislodged by (although not soluble in) water. Same stuff they use for dpc injection I think.

[N. Thornton]

Hi

If the builder rendered the whole place that is something of a caution sign. You dont generally render without good reason - although unfortunately some fools do. Walls are often rendered when its too much work to fix problems with them.

You could just water proof them. I'm doubtful this would be achieved with silicone fluid. Tarred surfaces stay waterproof far longer than oil based paints and so on. You cant easily paint over tar though.

Any waterproof paint would do for a while, but really you want something with good long life, as water penetration again would do a lot of damage.

And ideally use internal plaster that lets any dampness dry, like lime plaster. But only once the wall's properly dried.

many are rather gullible unfortunately.

I wouldnt expect either to solve the problem.

no

Penetration is liable to be patchy.

There arent by any chance cracks spreading out from some of the corners of the windows are there? If so, this picture might start adding right up. 1890s, soft brick, rendered, cracks at window corners, brickwork in poor condition under the render and wet: classic.

If that is the deal, a possible explanation may be:

1. Mortar between bricks in such poor state that the wall begins to move and crack
2. Bad mortar also allows driving rain to penetrate easily
3. Cracks start appearing in wall
4. Quick bodge fix for all of the above is to apply render.

The solution to this is to repair all the pointing - but there are important caveats with that. If that is your situation do get some more input before pulling render off, which may cause serious damage.

Any water penetration anywhere can be expected to freeze and slowly disintegrate whatever its freezing in.

Sounds questionable to me.

try toolstation.com, something like 1.50 IIRC

Good luck.

Regards, NT

[Meoww]

I'll taken even money you've cured it!

Another potential culprit was the actual seal of the window with the cill but it looks like you've done that one too!

If your rain today was like our rain today, you'll know pretty soon

0))

Keep us posted

Patrick

p.s. do you do weddings too - excellent photos ;-)

[Pete C]

Hi,

Make a little 'dam' of blu tack on the cill, fill it with water and see what happens.

Also might be worth pouring some water on the sill and checking any runoff doesn't flow round onto the render beneath. Could be worth treating those areas with silicone if you haven't done already.

Another possibility is that water is getting into the render next to the window and soaking down past the edge of the cil, so it could be worth treating those areas too.

Finally, if you've treated the cill itself with silicone you might have a job getting anything else to stick to it :(

cheers, Pete.

[Phil Addison]

On Wed, 23 Jun 2004 12:29:39 +0100, "stuart noble" >sill is still porous. Don't forget I have given a very generous sloshing

Had a look at it after some rain and was pleased to see droplets rolling around on the sill. I appreciate it may not last very long though (any estimates?)

Are you sure? I'm no chemist but once talked to the chemi-lab of the makers of Solignum when I was injecting it as a dpc. They told me that the stuff is not intended (indeed does not) fill up the pores of the bricks, but coats the internal surfaces of the pores with a very thin layer which changes the surface tension so that water does not rise past it. The upshot of this is that you can repeat the treatment if the first was inadequate.

See

[e-mail] for 1997 post.

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[Phil Addison]

That's what I like to hear - fingers crossed eh?

Had a look at it after some rain and was pleased to see droplets rolling around on the sill. I appreciate it may not last very long though (any estimates?)

No, I wouldn't dare. (*blush*)

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[Phil Addison]

I like that idea - very neat. I've got a packet of plasticine left from the 'glass-slip' condensation vs damp test. Wonder if that'll stick well enough. If not I'll buy a pack of blutak (hate the stuff normally - wrecks the wallpaper when the family get their hands on it!).

Yep, did all that, sprayed pretty much everything in site. The spray that got on the glass was a bugger to get off though. Meths and lots of elbow grease shifted it in the end. White spirit might have been better but didn't have any on site.

Doh... You mean like blutak or plasticene!!!

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[Phil Addison]

Eeek. I'll do some exploratory drilling to check the extent of this. Must say the brickwork under the patch I exposed is pretty ropey. I was going to repoint it before plastering, ut maybe I should render it (with no waterproofer additive) as well after all to bind it all together? OTOH, it only has a few courses to self support just there.

Had a look at it after some rain and was pleased to see droplets rolling around on the sill. I appreciate it may not last very long though (any estimates?)

I wasn't reckoning on tarring it - don't think my daughter would appreciate that.

any idea how long. As I say, it is done now with silicone, but I anticipate having to redo it unless I put an overcoat of something on, such as one of those recommended in this thread.

What is lime plaster?

OK, have given up that idea.

Well, there are some cracks around. I have already had to tie in the gable end wall (not where these windows are) that was found to be leaning out a bit when the loft conversion was done. I'll have a closer look at the corners next week, but I don't think we are in this scary scenario.

May well be, but with spar outside and *if* it is all rendered inside, difficult to be sure.

Absolutely. I have no intention of getting into that (I hope!).

Right. So a dpc under the sill is not the answer, so the sill must be waterproofed.

Just have to wait and see if it dries out, or the 'blutak dam' tells me anything.

Thanks. Noted for next time.

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[stuart noble]

IME 6 months or so.

I'm no chemist either but

might give you some ideas.