Garden wall tied into house wall, removal?

[ted456]

robodelfy,
Post #12 above will maybe help you understand why its a good idea to leave a gap below a BellCast?
Moisture rising from the ground is known as rising damp and will find its way up in the beds and perps, and sometimes through the brickwork until it meets the stop barrier of the DPC - thats why we have DPC's.
Moisture thats wicked up in the render will bridge or by-pass the DPC.

What your insulation installer was talking about i dont know - for a start good practice for external insulation mostly requires a clean, smooth brickwork background, definitely not a blown (Tyrolean) failing render with uncertain brickwork behind.
Your brickwork (a solid wall probably?) looks like it needs beds and perps hacking out and pointing and all the failing render removed.

 

[robodelfy]

I appreciate everyone's responses, although I'm quite confused now.

Why would render 'wick' up damp any more than brickwork?

The external wall insulation people said that it's not a bad idea to get off the really loose render but there is no need to get it all off if its stuck remotely well, as they mechanically fix the EWI and with adhesive. So not much can happen underneath. They also said little cracks here and there don't matter unless of course they are structurally unsound.

The company I'm going with seem to be one of the biggest and best in the south west, and have a lot of good reviews, seemed very knowledgeable.

 

[KenGMac]

robodelfy, good evening again.

OK Confused? not surprised.

First, "wicking" refers to the ability of ground water and any ponding water to percolate up behind the applied render, below the DPC and bell-cast, the water can / does by a form of capillary attraction rise up the interface of the render and the brick below the DPC.

As for "no render" below the DPC? the render may??? have been retro applied to "hide" poor or spalling brick [again] below the DPC, the brick work below the DPC is adversely affected by several things and water can "Get At" these bricks in various ways.
1/. Water rising from the ground.
2/ Direct rain.
3/. Rain splashing up from the ground, especially if the rain water gutter at roof level is leaking.
4/. And up here the action of Frost and freezing conditions can cause spalling to the face of the bricks below DPC.

So, the brick below DPC has a really hard time, and it is only because of the DPC that the wall above the DPC does not slowly become saturated, as happens to the bricks below the DPC.

So, on to loose render, and what to do with it prior to the installation of the insulation?
There are lines of consideration here, the external insulation, [it is claimed] can ??? trap any moisture that is present in the wall to be "trapped" inside the external wall. Where does this "trapped" water evaporate to? into the house, it cannot escape past the external retro-applied insulation.

I must admit, I am skeptical about such external applications, OK it is a good looking option and the advantages of not loosing internal space is good, combined with no mess internally is very appealing.

Getting back to loose or areas of render not adhering to the wall, such areas of render can / will allow rain water to get behind the render and start to make the wall wet, Any areas of such render should be removed and the wall allowed to dry naturally.

Ken.

 

[dontbelieveawordofit]

f@ck me! all he asked was . “shall i leave it until the ewi blokes turn up”
answer = yes.
he didn’t ask for a confused mixed up science physics biology college plastering tutorial more often containing bu!!**** answer to questions that dont exist.
bob is most defo in the room.

 

[JohnD]

Why would render 'wick' up damp any more than brickwork?

because the "wicking" is water moving up a porous material by capillarity.

if the material has the same size (small) pores the water can rise a long way

It will not readily move from small pores to large.

So, because, in clean, well-built brickwork, the pores in the bricks are not the same size as the pores in the mortar, water cannot easily rise more than a couple of courses

But if the wall is rendered or plastered, then it can.

Worse still, the render can bridge over the DPC, which should form an impermeable barrier to water.

This is why hacking off the render at the bottom will reduce damp in a wall.

Also, the water can evaporate off the bare brick, which also helps it to dry. The damp will stop at the point where the rising water (which is reduced by hacking off the render) is less than the rate of water evaporating off the bricks (which is increased by hacking off the render).

This is also why removing heaped up earth, or builders rubble, or sand and mortar inside a cavity wall, or improving ventilation under a floor, will all combat damp.

And not a single chemical needing to be injected.

Sorry, but you did ask the question.

 

[denso13]

Are you claiming that on the properties you've seen

I managed their construction.

Or are you claiming that the BellCast is installed but, for whatever reason, a smooth render is then spread below the BellCast?

It was a requirement of the Local Authority for homes built in the countryside. All still standing and no damp.

 

[denso13]

Here's one. Smooth render base course to ground level. The garage is the same and has 100mm block work walls with piers, therefore easy to see internally and no damp.

 

[ted456]

If you were the manager then why did you first claim you had seen loads of them as though you were a passing spectator?
Why have you avoided my questions? Evasions are not technical answers. Is that how you managed your site?

After first claiming that it was done to the latest Blg Regs and NHBC you now claim it was actually a requirement of the local authority - but only for homes "built in the country" apparently?
"All still standing" - as a construction manager do you typically expect rising damp to collapse buildings?

Do you expect anyone with trade experience to believe you when you claim this local authority has bypassed basic science, 100yrs of experience and common building sense, & forced you to build bad?

 

[denso13]

Do you expect anyone with trade experience to believe you

I really don't care what you or anyone else believes. What about the picture of the real world example I posted above? Or I am just making all this up?

 

[dontbelieveawordofit]

denso13,
You give excellent advice in the plumbing forum but what you are trying to nail down here is just flat out wrong, & could be expensive for a homeowner.

Most new rendered housing or new housing with external insulation has a BellCast fixed just above DPC level - its always fitted just above the DPC.
Are you claiming that on the properties you've seen that the render and maybe the insulation has no BellCast and drops straight down into the ground?
Or are you claiming that the BellCast is installed but, for whatever reason, a smooth render is then spread below the BellCast?
And are you claiming that the latest Blg Regs & NHBC specs have decided to ignore "wicking" "capillary attraction" and bridging?

how does ewi transport moisture from below dpc to above dpc?. agreed, best practice is to terminate ewi just above dpc but not essential and not even necessary in cavity wall build.
and the point about bellcast is also incorrect. a bellcast is pointless at the bottom of ewi that already sits at least 50mm proud of the substrate.

 

[dontbelieveawordofit]

I really don't care what you or anyone else believes. What about the picture of the real world example I posted above? Or I am just making all this up?

search bobasd . nightmare!

 

[denso13]

only brickwork should show below the Bellcast.

And as the OP is having an EWI system fitted here is a below DPC detail. It doesn't have to be "only brickwork" showing.

 

[ted456]

I've just seen your post #22 pic. And that is not what is being talked about on this thread - stay on page please. No ducking and diving.
On your Post # 8 you say "like that" meaning in the context of the original pic.
I, and many others, could come up with pics and experiences of all kinds of render designs but here we are talking about whats on the page
while using the OP's pic as a reference point.
Perhaps you didn't know but you can only compare like with like.

In post#22 I do note your point in the pic that the smooth render goes into ground contact - well thats flat out wrong.
You dont use a BellCast for such circumstances you use an unobtrusive plastic stop bead to keep the smooth render from ground contact.

 

[denso13]

Here is another example of smooth render to ground level taken from a Local Authorities "guidance on housing in the countryside". The first one I looked at but I suspect most are the same, my LA is.

well thats flat out wrong.

I've shown you real world examples where it is done, and the first one has Building Control sign off and an NHBC warranty.

I've shown you a technical document showing below DPC fitting of an EWI system.

How about you provide evidence or guidance proving your position rather than relying on this...

100yrs of experience and common building sense

 

[denso13]

In post#22 I do note your point in the pic that the smooth render goes into ground contact - well thats flat out wrong.

There is no damp showing internally. How can that be?