Within the window industry, especially with regards to conservatories, window companies put great trust in their sub-contract builders - often giving no regard to exactly what the sub-contract builder is doing. This is a dangerous thing to do, writes Don Waterworth.
I would advise that you take great care in not only choosing your sub-contract building contractor but also ensuring that the building contractor is carrying out the work effectively.
If you are a member of the MWCIA, then you can check technical details on our membership call service. However if you are not, then you must find suitable specifications from Building Control or other technical bodies and ensure that your builder is provided with these.
It is folly to allow a building contractor to simply turn up at site and carry out the base and dwarf building works without any checks on the contractor at all... unless of course, you've worked together on a number of previous jobs.
My own inspections
I have inspected many conservatories where the sub-contract builders have dug the foundations too narrow, too shallow, carried out the brickwork to an appalling standard, not protected drains, laid floors incorrectly, etc. Also what can occur is ‘bridging’ of the DPC as shown in photographs accompanying this article.
In the photographs here it can clearly be seen from the outside that the courses of brick at the conservatory base do not marry in with the existing house brick. This in itself is not detrimental as bricks can be different sizes depending on the age of the property. However take a closer look and note that the top course of brick underneath the PVC cill sits higher than the DPC level on the property. This is a particular problem, as the internal skin brickwork is obviously set at the same level and therefore when tiles were laid on top of the concrete slab, the tiles sat higher than the DPC, i.e. 'bridging the DPC'.
This allowed damp to track across from the outside to the inside (rising damp), bridging the DPC and causing dampness within the conservatory wall and floor.
The company were at a loss as to what was causing the dampness in the conservatory and assumed it was condensation. However an inspection showed that it was not condensation but moreover the amount of moisture being created in the conservatory by the bridging of the DPC and the DPM, due to the high level of the brickwork and hence the finish level of the floor.
Remember that you are liable for the workmanship of your sub-contractors with regards to Contract Law.
Yes, it is true that you can pursue your sub-contractors thereafter, if your sub-contractors are proven to be liable with regards to poor workmanship.
However pursuing the sub-contractor is a long-winded process. You would require an Expert Re- port and then more than likely you would need to issue a Summons against the sub-contractor as he may argue that, of course, he has done nothing wrong.
So the consequence of matters of this type as shown in the photographs is that the window company had to lift all the ceramic floor tiles, break up the floor, reduce the floor level, pay for the re-tiling, the cost was £2 - £3,000, which then had to be levied against the sub-contractor.
Therefore, take time to find a professional sub-contractor. Pay the right price for the sub-contractor and I would suggest that your Surveyor makes regular visits to inspect the building work being carried out by the sub-contractor, therefore ensuring that the works are completed to a satisfactory standard and that your company is not ultimately liable for works carried out by others.
Artical first published in The Installer Magazine, June 2016