What causes a house extension to collapse?

A common problem when extending a house is the settling of the extension after a period of use, causing inconvenience and safety concerns.

One of the most common house extensions is the kitchen, which usually involves expanding the existing kitchen at the back of the house to create a larger room, demolishing the original walls, and then building the floor and roof flush with the original house walls.

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However, after some time, settling of the floor occurs, cracks appear in the walls separating from the main house, and the newly constructed roof leaks. This is quite common. Is it possible to prevent these problems from happening?

Preventing settling and cracking is generally possible to a certain extent. This is because extensions or new structures built adjacent to existing ones will inevitably settle unevenly. The original structure may have stopped settling, while the new structure will continue to settle.

Therefore, uneven settlement of adjacent structures leads to cracks or gaps.

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Severe cracking and settlement after structural additions often occurs when new foundations and piles are constructed only on the expanded side, and new beams are connected to the original house structure using only reinforcing steel rods.

As the new structure settles, the joints are pulled apart. The correct approach is to construct a proper foundation for the added structure.

However, this is sometimes impossible due to insufficient space. Uneven settlement between the new and old structures is unavoidable. Therefore, preventative measures must be taken when settlement occurs in the adjacent walls, by sealing the joints with materials to prevent rainwater ingress.

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If there is sufficient space to construct a new structure with piles of similar length to the original structure, a bored pile system would be necessary. The minimum bore diameter required for bored piles is 3 meters, but this can lead to cost overruns.

Methods to prevent or minimize this problem are crucial. It's essential to find a contractor who understands the mechanisms of structural settlement. An engineer would be ideal, as they can assess the situation and determine the best foundation method. They must also explain to the owner how settlement can be prevented or slowed, and whether the new structure will be connected to the existing one.

Preventing settlement and cracking during structural additions is both possible and impossible, depending on the area. For large-scale additions, such as those exceeding one story, an engineer should be the one to determine and design the plan.

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Structural additions can be difficult and prone to unforeseen obstacles. For example, additions may affect drainage or plumbing systems. Finding trustworthy personnel to ensure the homeowner's safety is crucial. Furthermore, construction costs are generally higher than regular construction due to the need to account for potential delays.

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Thank you for the helpful information from HOME.