Advice on rendering????????

No probs - add a waterproofing admix to the render.

 

Don't think that's quite acceptable......



Mr. HandyAndy - really

 

render shouldn't be above floor level in this application because it will jump the dpc causing damp!!

 

the thing is it hard to know where the dpc will be , because you inject into the brick and not the bed so you don't know where to put a bell bead . so you have just got to guess or just render down and put the required waterproofer in

 

Why is not acceptable?? do you no a way to do
it???????


You MUST keep the separation of the damp course intact.

You compromise it if your render below it and above it, effectively rendering(pun intended) the dpc useless.

A-
'A' way to do it is this.


Render up to(or very slightly below) the damp course, finishing with a 25° slope down and outwards from the dpc.

Apply a bitumen or Pitch Epoxy coating from the outer edge of your 'slope' all over the existing dpc and up the wall 150mm. This is your 'drip-tray' separating the above and below dpc areas.

Now render the above and right down level and flush to your original 'outer edge of slope'.

Dpc intact.

If you search hard enough, you can find coloured pitch epoxy and, I believe, clear, so your join can be hardly noticable.

Hope that helps.




Mr. HandyAndy - really

 

Disagree - even if the render 'causes damp', (render WILL NOT cause damp - retention of water causes damp), where is the ephemeral damp going to go?
Is it going to miraculously leap across the cavity as well as jumping the DPC?
Provided that the cavity work is constructed properly, eg not bridged (usually caused by incompetant bricklayers not cleaning the cavity), if there is water present against the outer leaf, the outer leaf will get wet, (perhaps similar to whrn it rains), and when the water goes, the outer leaf will dry out again.

 

Oh dear. So all these years they've been putting a dpc in the outer leaf about floor level and it's all been a waste of time and money ? And all those renews of damp courses. All a waste of money ?



Mr. HandyAndy - really

 

The external dpc does not go about floor level ,it goes 6" above ground level your dpc should not be 8 bricks high. Make sure your render stops about 2 bricks up and you should be OK

 

Yorkshire boy. You're wrong.


Mr. HandyAndy - really

 

Oh dear. So all these years they've been putting a
dpc in the outer leaf about floor level and it's all
been a waste of time and money ? And all those renews
of damp courses. All a waste of money ?



Mr. HandyAndy - really


Tell me, then, how a damp external wall makes an internal wall as damp?

 

Oh dear. So all these years they've been putting a
dpc in the outer leaf about floor level and it's
all
been a waste of time and money ? And all those
renews
of damp courses. All a waste of money ?



Mr. HandyAndy - really


Tell me, then, how a damp external wall makes an
internal wall as damp?



The damp external wall make the insulation damp and the damp insulation makes the internal wall damp. It's called bridging the cavity.

Under normal circumstances, the rain is assumed to hit the outer wall and have enough time to dry out before getting through the brickwork.

Rising damp on the other hand(the reason for dpc) stays damp and increases in damp all the time, therefore damp rising above the dpc on the outer leaf will be damp for a long time and increasing so has a good chance of dampening the insulation and therefore the inner wall.

If rising damp rises up from ground level on rendering, it will rise up above the dpc, stay damp/increase in damp an take longer to dry out(the render acting as a barrier to the brickwork and keeping damp in), hence the need for a dpc in the rendering, if the rendering goes down to below dpc level.



Mr. HandyAndy - really

 

The area in question is 8 bricks below the floor level so there won't be any insulation, there will be a clear cavity.
The only cavity insulation which would wick damp through would be the old granular stuff .Handyandy you seem to persist in posting detailed answers about situations you appear to have no practical experience of.I try but I don't allways have time to correct you....

 

The area in question is 8 bricks below the floor
level so there won't be any insulation, there will be
a clear cavity.
The only cavity insulation which would wick damp
through would be the old granular stuff .Handyandy
you seem to persist in posting detailed answers about
situations you appear to have no practical experience
of.I try but I don't allways have time to correct
you....



So, 1, if you fill a cavity with insulation(post-build), it doesn't go below floor level because something stops it ?

And 2, the area in question is 8 courses below floor level, and by your reckoning the dpc will be 6 courses below floor level.


Balderdash.



Mr. HandyAndy - really

 

could you just go over that again lads .

cheers jj

 

The damp external wall make the insulation damp and
the damp insulation makes the internal wall damp.
It's called bridging the cavity.

You are, of course, making the enormous assumption that the cavity is fully filled..............you are also assuming that any insulation present is 'wettable', eg capable of absorbing and retaining moisture into it's structure rather than the moisture just lying on the surface of the insulation fibres which would not cause wicking.

 

You can render below dpc perfectly well without fear of the slightest problems, 70,80,000 Irish homes are built annually, the vast majority rendered IN FULL as they are block built, I have done more of theese than can be shook a s*ty stick at. My own home included. Jules is spot on Handyman sorry, you are wrong wrong wrong!!!