Unable to locate DPC
The BBA Cerficate for our CWI Agrément Certificate No 01/3789 states that the bottom row of drill holes should be maximum 800mm above the damp proof course (DPC).
|Agrément Certificate No 01/3789|
The DPC is quite tricky to spot because the bottom row of bricks are undrendered but painted black. The home buyer surveyor was not able to identify the DPC and two CIGA inspectors did not look or document it despite concluding that the installation was done to system designer's specification.
It's not possible to assertain if the installation was correctly done to industry standards without locating the DPC. CIGA have stated that drill hole patterns were the key factor in their conclusion of conformity but have told me it would be unreasonable for me to have that information (I was present for both inspections and no measurements of drill holes were done).
For my property one might ask which DPC? The 1960s extension has a brick external leaf which has been tied into the original back wall but the DPC is a full brick higher then the original (the current recommendation is that DPC is 150mm above ground).
|Variable height DPCs|
Unfortunately the way that the join was done means that there is a potential for water transfer via capillary action which is blocked by the 1960s dpc to bridge the 1930 DPC as per diagram. Since the cavities are not continuous, there is a brick bridge between the external and internal leaf at this point and so the moisture can travel to the internal wall also.
What do the insdustry standards say?
The CIGA installer guides Clearly sates that a bridged DPC means that the cavity must not be insulated.
|CIGA Technician’s guide to best practice Version 2.0 - Issued July 2002|
So that's fail number one.
Checking the height of the lowest row of drill holes:
The bottom drill holes are indeed approximately 800ml in the extention but the installers continued along the bulding at the same level and in the old part of the building they are too high by 17.5% from the the BBA certificate.. There are predictably large voids. Fail number 2.
CIGA have said that the drill hole patterns were part of their conclusion that the CWI was installed to industry standards and while I welcome a change in heart and them supplying the mythical measurements. I know for a fact that these measurments were not done and there is a serious probity and professionalism issue here.
This is a company which has just been awarded a Trustmark scheme provider.