Treatment of old brick wall below ground - bitumen?

[AMc]

What do you all reckon about having a non-breathable coating on the walls to above ground level, then switching to the breathable system? He's not recommended non-breathable materials anywhere else in the building, but feels that where the wall is below ground, the risk of ingress of ground water is more significant that the drying afforded by the breathable finishes.

Any views?

Is there any reason to use bitumen on the bricks as opposed to laying a plastic DPM against them and back filling below ground?
At least that would be reversible and would (probably) provide a more water tight barrier than a painted finish which I doubt will ever be 100% impermeable.
I may have misunderstood what is being proposed but I figured I'd make the suggestion.

 

[JoceAndChris]

If an "expert" told me to paint underground bricks with bitumen I'd ask them to jump down into the vaulted rainwater chamber and take a good look at those walls, painted 25 years ago. The bitumen fails and the water seeps where it wants to seep. What was the point of painting them?
Zebra, I'm not with you on your exterior wall insulation plan but it's your house and totally up to you. But I'd be going for French drains, lime render, limewash and more thermals and fleeces in your wardrobe.

Just had guests here - Mum, plus her little protege - the neighbour's child. I specifically asked that he be sent in many warm layers and they sent him in a T shirt, so I've had to put fan heaters on all day. Grrrrr. It makes me seethe. Old houses are cold and should be cold, money should be spent on better things than heating. There ought to be a law against T shirt temperature in winter, I'm with Biff on this, it's inter-generational injustice or whatever they call it.


Grr, rant over, and I accept all charges of being a boring old purist.

 

[Lime]

Send the child up the chimney.
That'll soon warm them up.

 

[LadyArowana]

If an "expert" told me to paint underground bricks with bitumen I'd ask them to jump down into the vaulted rainwater chamber and take a good look at those walls, painted 25 years ago. The bitumen fails and the water seeps where it wants to seep. What was the point of painting them?
Zebra, I'm not with you on your exterior wall insulation plan but it's your house and totally up to you. But I'd be going for French drains, lime render, limewash and more thermals and fleeces in your wardrobe.

Just had guests here - Mum, plus her little protege - the neighbour's child. I specifically asked that he be sent in many warm layers and they sent him in a T shirt, so I've had to put fan heaters on all day. Grrrrr. It makes me seethe. Old houses are cold and should be cold, money should be spent on better things than heating. There ought to be a law against T shirt temperature in winter, I'm with Biff on this, it's inter-generational injustice or whatever they call it.


Grr, rant over, and I accept all charges of being a boring old purist.

T shirt in UK in December? What was his mother thinking. I thought it was obligatory for littlies to be told to wrap up warm, whether visiting a period property or not. I wear lots and lots of layers ( but still need the heating on or I get all cold and wrinkly ) and run about, but have still managed to catch a nasty Japanese cold bug.

 

[JoceAndChris]

Poor LadyA. I understand it's pretty nippy in Japan in winter and many houses aren't particularly adapted to that. I remember my Japanese ladies would stick those heating pad things up their backs and on their tummies, I thought them excellent but probably not very green. Get well soon.

I like the idea of sticking the boy up the chimney; children are far too spoilt and useless these days.

 

[Flyfisher]

T shirt in UK in December? What was his mother thinking.

Having given the advice to wrap the little darlings up warm, perhaps that's what their Mother did?

FF junior seems quite happy in a Tee during winter but finds hot weather rather more uncomfortable than I would say is normal. I put it down to years of whitewater kayaking having messed up his thermostat. He's quite happy to break the ice to get into a river and the first thing that most kayakers seem to do after launching into the water is to do a full roll, no matter the temperature. Icicles in the hair are not unusual during extreme weather.

Joce should have switched off the fan-heaters and just made them run around the fields in their Tee shirts.
A chimney would be good second choice though. :wink:

 

[Feltwell]

Kids don't tend to feel the cold unless they're tired, or at least mine don't.

Taking my 7 year old daughter as an example - who has no "natural insulation" at all, she's very slender - she'll quite happily wander around the house barefoot in a t-shirt and leggings, when I'm far more wrapped up. Ask her if she's cold and most times you get "I'm fine, thanks" as an answer.

One of my childhood memories is my mother, who has always felt the cold, nagging me to wear a vest and wrap up when actually I was fine and was far too warm if I dressed as she wanted. She gave up nagging in the end!

 

[Zebra]

What do you all reckon about having a non-breathable coating on the walls to above ground level, then switching to the breathable system? He's not recommended non-breathable materials anywhere else in the building, but feels that where the wall is below ground, the risk of ingress of ground water is more significant that the drying afforded by the breathable finishes.

Is there any reason to use bitumen on the bricks as opposed to laying a plastic DPM against them and back filling below ground?
At least that would be reversible and would (probably) provide a more water tight barrier than a painted finish which I doubt will ever be 100% impermeable.
I may have misunderstood what is being proposed but I figured I'd make the suggestion.

That's a very good point AMc. I'll put that to the architect and see what he says.
Or I wonder what would be the effect of having no barrier at all. I'm not sure I agree with the architect that the effect of penetrating ground water would be significant enough to warrant a barrier - even though the bottom 300mm of the wall is below ground level, there shouldn't be any penetrating ground water, that's what the French drain is for..

Zebra, I'm not with you on your exterior wall insulation plan but it's your house and totally up to you. But I'd be going for French drains, lime render, limewash and more thermals and fleeces in your wardrobe.

I hear you J&C, I know it's not traditional, and perhaps I should just be putting back its traditional laths and lime render... :?

 

[MdB]

I've never quite understood the idea of putting a sheet of plastic up against a buried wall (the same would apply to a coating of bitumen), a previous owner had done that here. All that occurs is that the moisture goes underneath the bottom edge of the sheeting with the moisture content ending up very similar to if there was no sheeting there at all.

 

[middi]

I've never quite understood the idea of putting a sheet of plastic up against a buried wall (the same would apply to a coating of bitumen), a previous owner had done that here. All that occurs is that the moisture goes underneath the bottom edge of the sheeting with the moisture content ending up very similar to if there was no sheeting there at all.

Absolutely right, MdB.

A solid plastic sheating resting against an exterior wall below grond level will achieve absolutely nothing, and only marginally better if a " corrugated" stiff plastic sheating is used in a similar way ( due to the ventilation factor achieved by the corrugated segments ). This latest application is a favourite on the continent to " repair" cronic rising damp in older ( and sometimes new !!!) properties , it is used in conjunction with a french drain.

Middi

 

[Lime]

Or I wonder what would be the effect of having no barrier at all. I'm not sure I agree with the architect that the effect of penetrating ground water would be significant enough to warrant a barrier - even though the bottom 300mm of the wall is below ground level, there shouldn't be any penetrating ground water, that's what the French drain is for..

Yes exactly.
The only benefit a waterproof membrane of any sort may have when on or against a subterranean wall is to repel inundation.
Otherwise all it will do is hold water in the wall all the time and prevent it coming out.

 

[AMc]

My understanding was this was to repel water coming in from above/beside not rising from below?
I would imagine that if the wall is drier and more porous than the soil stacked against it then moisture would migrate from the soil into the brick more readily than the other way around, but I'm still not convinced this is any reason to do it.
My suggestion was simply the bitumen would be irreversible and would be even less likely to work in the way the architect thinks it will, than a single impermeable sheet of plastic. A sheet of DPM would also be much cheaper given how long it takes to paint exposed brick.

 

[Zebra]

AMc you are right in that the architects suggestion was that the waterproof layer on the brickwork below ground was to repel water coming in from the ground beside or above. (He suggested an injected dpc to prevent rising damp, but let's not get into that...). However,there isn't soil stacked against the wall. I have a French drain against this wall, which takes the water away, and is filled with gravel, to the depth of the foundations, which is a course or two below internal ground level. So my point of view was that the French drain should be taking away any water coming from the side and I wouldn't need a barrier...
His view was that below ground and behind a layer of gravel, the effect of penetrating rainwater would nevertheless be greater than the evaporation rate, therefore the wall would be getting wetter not drier if there were no barrier.
If I don't have the injected dpc, then I think the barrier will be doing more harm than good. So I reckon I'm against it, whether bitumen or polythene.
But I do take your point AMc that polythene would be removable whereas bitumen wouldn't.....

 

[Matt Green]

A tricky one. You are effectively changing the water management strategy of the wall from breathable to non-breathable by installing the external insulation, I can see why the architect would want to go for a fairly thorough water exclusion strategy. As long as the wall is dry and entirely likely to stay dry, there should be no problem with lining the external side of the wall below ground level with a DPM. If it ever gets wet, it's going to cause you problems though.

Matt

 

[Lime]

A tricky one. You are effectively changing the water management strategy of the wall from breathable to non-breathable by installing the external insulation, I can see why the architect would want to go for a fairly thorough water exclusion strategy. As long as the wall is dry and entirely likely to stay dry, there should be no problem with lining the external side of the wall below ground level with a DPM. If it ever gets wet, it's going to cause you problems though.

Matt

But is IS going to get wet, isn't it?

 

[Zebra]

You are effectively changing the water management strategy of the wall from breathable to non-breathable by installing the external insulation

Well, yes and no. The woodfibre external wall insulation will be breathable, it is only the bottom part of the wall (up to 300mm above external ground level / 600mm above internal ground level) which won't be if I use the bitumen.
I suppose they want, as you say, a thorough exclusion strategy, because woodfibre external wall insulation doesn't work very well if the wall is wet.