Can anyone explain a building technique used in my house and most of the
properties in my area which were built between 1910 and 1930
The houses are built of brick, and have a render "skirting" of less than a
inch thickness that goes all the way around the property up to a foot or so
above ground level, with a 45 degree angle at the top taking it down to the
brickwork. Some houses are double wall, others solid wall.
My question is: what, if anything, is underneath the render ? ( I don't want
to hack off to find out)
Typically, did they install a vertical DPC such as coats of asphalt, or is
it just a coat of render?
Reason I ask, is that I have been reading that render should not be allowed
to bridge the horizontal damp course - which I assume is underneath it
somewhere. - Or were properties from this period (1910-1930) not usually
built with damp courses??
If anyone out there has ever hacked off their render "skirting" and can give
me some clues, I'd be grateful
Are these skirts outside or inside?
If they are inside, do they go below the floor? I don't believe they had
damp courses in those days but used air bricks with a space under the
If they go around the outside, then obviously they serve as watersheds.
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They are external "skirts" ( dunno if that is the right term)
What I don't get is if the are supposed to be effective, won't they need to
be waterproofed somehow ? If they are a lime mortar, and don't have an
internal vertical seal, won't they be of limited benefit ?? And if there is
a physical dpc, won't they bridge it in exactly the way we are told you
When moisture is absorbed into lime render, I'm told it is only drawn
into the first 2mm, so if the skirt is thicker then that then it
should help. 2mm seems very little to me, but who am I to argue with
~~ Anna Kettle, Suffolk, England
|""""| ~ Lime plasterwork, plaster conservation
/ ^^ \ // Freehand modelling and pargeting
|____| www.kettlenet.co.uk 07976 649862
I saw some recommendations for building materials for houses
on flood planes somewhere on one of the government websites
a year or so back. One of the comments there was to suggest
the use of lime plaster, as it apparently is much less likely
to need replacing after being submerged.
This image of lime mortar like a sponge isn't right and in practice
lime mortar doesn't absorb damp all the way through. I've removed
soaking wet lime mortar and a little below the surface it is dry as a
bone. I suspect that water soaks into the surface and the clogged
pores then act as a buffer inhibiting more water from getting in.
Almost certainly an attempt to counteract 'ground splash' - if you look at
walls in heavy rain, the lower 6" or so gets wet from rain splashing up from
the surrounding ground surface. Failing that explanation it COULD just be
decorative, or perhaps repairs to spalled brickwork caused by the ground
splash or rising damp below a DPC followed by frost. I did have a house a
few years ago (built 1898 iirc) that hade standard sized roof slates
embedded in a plinth such as you describe, but wether it was original or a
later attempt at damp control was a matter of conjecture.
Houses in the period you mention will pretty certainly have some form of
dpc - earlier ones being slate and later ones bitumin ( though my 1903 house
breaks that rule by having bitumin). Both fail over the years from slight
movement of the structure.
In the case of my 1903 Edwardian house, again rather unusually, the
foundations are mass poured concrete, BUT the original DPC was put in AT
ground level directly on the footing concrete, and not at the more usual 6"
above ground level.
But don't bet on having a damp proof course, my 1906 house, as originally
built, had no damp proof course, suspended wooden floors (and no air brick)
and the foundations are just a widening of the wall to about double width
(becoming 18 inches) but only six inches deep, Oh and the other half of the
house has flint foundations. (I'm only 2 feet above the winter ground water
I would suggest you don't have a DPC as that wouldn't work with the render
The render foot is common around here to prevent water splashing as
previously noted , it is often tarred, as well to increase the proofing.
I am 99% certain the plinths /skirtings here are original, as every house
around here has them and they seem to be identical between properties.
I have seen horizontal damp courses which use offset layers of slates
between two courses of bricks. I wasn't clear, did your 1898 house have
this, or did it ( also) have slates embedded *vertically* in the plinth to
give protection from damp entering horizontally????
> Houses in the period you mention will pretty certainly have some form of
Reason I am asking is not purely academic. I have inherited a small property
(not the house with the render skirtings) which had no dpc - and which
suffered from rising damp. However, I understand that the external render
( no skirt, just flush) , if restored, will bridge the chemical dpc I had
injected, and I was wondering if the use of a skirting with embedded slates
/ bitumen layers was a recognised technique I could apply. The alternative I
believe suggested by the dpc company was a "bell drip", but this will still
result in a layer of render bridging the dpc underneath the drip, if I am
not mistaken. Putting a waterproofer in the render would invalidate the dpc
guarantee, I am told, so I was wondering if there was a physical technique.
It's a heck of a long time ago to remember ( 29 years !) BUT IIRC in the
1898 house there was a slate dpc as well as the slate vertically in the
plinth - however it had failed (heavy clay soils hence movement) and had
been supeceeded by an injected DPC in every brick of one course.
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