What does dislocated (ontzet) mean?
The Dutch building term ontzet means that an element has come out of its bond: it has shifted, settled or cracked and no longer stands where it should. It is used above all for foundations, walls, piers and vaults.
Such an element is more than cosmetically damaged. Masonry owes its load-bearing capacity to its bond and to the continuous compressive force running through the wall. As soon as courses move relative to one another, or a crack runs right through, the load path changes and the strength can drop considerably.
Common causes
- Differential settlement of the foundation — the classic picture: a vertical or stepped crack running diagonally upward from below, wider on the side that is settling.
- A falling groundwater table — with timber pile foundations, exposure above water leads to pile rot and therefore to settlement.
- Impact or shock loading — on corner buildings, piers and façades along the carriageway.
- Spreading forces from vaults or roofs — a roof structure that spreads pushes the long walls outward.
- Excavation or vibration next to the building — an excavation, piling works or heavy traffic.
- Missing or corroded ties — in cavity walls and in old façades with wall anchors to the joist floor.
What to do
- Measure before you repair. Fit crack monitors or take level readings along a bed joint and establish over a few months whether the damage is still moving. A dormant crack calls for something entirely different from an active one.
- Look for the cause, not the symptom. Filling cracks without addressing the settlement produces the same crack again within a few years.
- Bring in a structural or foundation engineer where cracks run right through, floors slope or doors bind. A foundation investigation soon costs several thousand euros, but it prevents repairs in the wrong place.
- Repair with intent — stitching in new brickwork, bonded reinforcement in the bed joints, new ties, or, where settlement is severe, foundation underpinning.
Related terms
- Settlement
- Reinforced masonry
- Groundwater level
- Movement joint
- Pile foundation
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