Existing extension separating from building

Structural engineer report advise under pining

Hi Mark I see some responses here have referred to a structural engineer's report and rightly so, though this may cost between £600 to £1,000 + VAT, depending on where you're located in the UK. It's worth noting the gap could be an expansion joint which must be 10mm wide. You mentioned at 'few centimeters' which is a concern. Is the gap larger at the top than the bottom of the wall? Can you see daylight from inside the house? If yes, get a SE report now. Bricklayer's can leave a vertical movement joint on the outer leaf of the cavity wall, where the new extension meets the existing building. On the inner leaf of the cavity wall, wall ties or wall starter kits are used to structurally tie the new extension to the existing building. Overtime, the outer vertical movement joints can be rendered over, and cracks/gaps form later, due to thermal movement. In this case, a reputable builder must remove render and install fibre board in the movement joint and make the surface waterproof by applying a polysulphide sealant. Hope this helps.

Fully agree with a structural report also contact your building insurance company and the builder who constructed your extension and check it was signed of correctly by building regs. Best Regards Mark

I will advise to inspect the foundation and the dpc level if the problem is coming from there. If yes, that side wall of the extension needs to be break down and rebuild again with reinforce on the foundation. Get a site engineer to survey the property before any work. Best of wishes Rochete engineering services RES