Exposing DPC for cavity wall insulation

[chris_o]

Been asked to do some work for someone as they're having cavity wall insulation work soon.

The firm have requested that the DPC needs to be exposed, which is understandable. He wrote this:

This is the side of the house

Assuming the DPC is directly under the air brick, do they want that exposed from there down to ground level? Or 75 to 100mm above the DPC exposed and then fully down to ground level?

I will contact them, but they're not avaiLable again until Monday!

 

[vinn]

Usually you hack off 150mm below the DPC to the ground. The Dpc should be in the bed immediately below the air brick but thats not always the case.
Rear elevation OK -
Just needs render removed, is he talking about below the Dpc or removing all the render?
For the time being why not just remove the 150mm below the Dpc?

 

[tony1851]

Why not give them a ring and ask them?

 

[freddiemercurystwin]

Because they're not available until Monday and waiting is not acceptable.

 

[chris_o]

Yes, exactly that

 

[tony1851]

Sorry - couldn't find my specs

 

[KenGMac]

This entire proposed enterprise is wide open to interpretation? and fraught with a probable on-going argument?

The shall I call it wording of the request from the Cavity Wall insulation installer is bluntly Crap!

As an aside what if there is no DPC? or the DPC position cannot be determined, or as I see regularly the DPC steps up and down even on a level to the ground wall?

There is another as I see it, problem that being if you cut the existing external render, there will be spalling and break out above the cut line? excess vibration could cause the remaining render to De-bond?

How will the cut lower edge of the remaining render be made water tight, any thoughts on a drip, and how to form it? so that rain water on the external surface of the render drips off and does not run on to the top of the DPC.

Going back to my opening, what if?
1/. You dislodge an area of remaining render? will you be responsible to re-paint the entire wall? at whose cost?
2/. The cut will have to be angled so as to form a drip to shed the rain water.
3/. there is no mention of surface finish to the brick that will be exposed when you remove the render?

As above, interpretation / interpretation / interpretation?

You could be leaving yourself wide open to who knows what?

OK I am possibly being shall I call it Cautious? But?

Ken.

 

[freddiemercurystwin]

Cavity wall insulation surveyors are generally clueless as to what properties are suitable and those that aren'. They're just box ticking robots who just want to get their fee, your number will be blocked quicker than the installation will take if there is a problem.

 

[Nige F]

I can't think why the DPC needs to be exposed for CW insulation

 

[vinn]

The recommendation to remove the render at the DPC is because the cavity insulation co. dont want it bridging the DPC.

 

[freddiemercurystwin]

The recommendation to remove the render at the DPC is because the cavity insulation co. dont want it bridging the DPC.

Why?

 

[KenGMac]

freddymercurystwin, hi

The all singing all dancing completely buildings savvy Cavity Wall installer will, it is claimed insert a Baloon to prevent the beads or what ever crap they are now telling us is the best thing ever from filling the cavity below the DPC so that the DPC is not bridged inside the cavity, what these ExPeRt Installers fail to note is that the DPC is already bridged by the external render, must be the very dark sun glasses they all wear???

Why? because the installers are slowly coming under very, very serious pressure from their Guarantor Insurers to ensure that they try to cover all the bases to mitigate a future Claim for a failed installation where the internal walls become complete saturated by the fill failing and causing, very expensive problems?

OK if the Installer installs a balloon to stop the fill dropping below the DPC, FINE, but? how do they ensure that the balloon remains level in the cavity? must have X-Ray Sunglasses? then what happens when the balloon is removed? it appears that Gravity does not affect the bead fill? in that the bead fill will somehow remarkably remain in place, that is it will not fall into the void, however deep it is, which will disturb all the bead fill above to induce voids in the bead fill in all sort of places in the wall?

There is a recent trend for the one time installers to close down the installer business and pop up again as removal so called specialists??? the really nasty and oft time failing Cavity Fill is the dreaded Blown Fiber, this combined with an even moderately porous external brick = you would not believe the cost to repair.

One bit of advice to the original post chris_o is to ensure that the installer is fully and completely and totally backed up by an insurance product. Check the provenance of the insurer, and Please, Please retain the papers and especially the insurance guarantee, if, and I really hope it does not go wrong this sort of detail may, I stress MAY! be needed if the fill fails.

Then again as I work as an Insurance Claims Surveyor, who knows I may pick up some Surveying work to rectify failed Cavity Wall fill.

There is a burgeoning lucrative industry growing around failed Cavity Wall Insulation, both on the removal side and the associated insurance claim for extensive damage to the property, both internal walls and external render and all associated finishes, believe me an insurance claim like this has an astronomical cost.

Ken.

 

[vinn]

Here are some of the items on the cavity insulation surveyors check list that would tie-in with the question above.. Thats if they are working to a recognised protocol

To expose any existing DPC.
Confirm that a DPC is present.
Functional DPC's must be present on both skins.
All air bricks to be above the DPC's.
To reveal any cracked brickwork.
To reveal any blown bricks.

Some of the items are self explanatory. Other items are checked so as to remove possible causes for disagreements after any complaints.
Any render bridging of a DPC might allow capillary action to soak through possibly damaged wall areas above the DPC.

 

[freddiemercurystwin]

Yes yes yes but how does our Messiah know there is even a dpc or where it is? He's just doing what his Q&A spreadsheet tells him.

 

[KenGMac]

freddymercurystwin, Hi

Just follow the check list as complied by the guarantor Insurer, tick the box, move on and everything is OK.

Hope it is not a solid brick wall with no cavity??

Up here, the Surveyor is supposed to use a bore scope or cut a hole into the external brick to see if the cavity has been filled historically [as if you could not see the fill hole[ and bodged repairs of the holes?

Ken.