Lateral stability is often misunderstood and underestimated when it comes to the design of a home. Lateral Stability is a structure’s ability to resist horizontal loads or forces, most commonly wind, earth, and in some cases earthquakes, seismic loads.
Wind and earth horizontal loads
Wind loads can not only be applied to the surface of a structure, as you might expect, they can also be applied away from the structure, causing suction or uplift. These are called positive and negative pressures. You need to be sure that your structure is strong enough to resist wind loads and sufficiently anchored to the ground.
Earth loads are only relevant in basements and retaining walls. The soil around your excavation naturally wants to move down and sideways, like when you are building a sandcastle and you turn a full bucket upside down and remove it – the sand will fall down and out. This force is applying itself around your basement walls and looking for any weakness.
Hydrostatic pressure is where the soil expands due to moisture and exerts pressure on the external walls pushing them inwards, which can cause a crack in a basement wall, leading to leaks. Read more in our ‘Why is my basement leaking’ article.
Without sufficient lateral stability a structure’s walls are likely to collapse, whether above or below ground, or the building is at risk of literally blowing away.
Achieving lateral stability
Several factors can affect the lateral stability of a structure including the form of construction, building height and the soil conditions. In design terms doing anything that removes a source of lateral stability will mean that an alternative means of resisting the lateral loads will be required.
Traditionally built houses are stable by their nature as the outside walls (big box) are formed by a series of rooms (little box), often referred to as “cellular” in nature.
If you are removing masonry, to add bigger windows or a bi-folding door then you will be breaking up the cellular nature of the building and may be necessary to reinforce your walls with wind posts and bed joint reinforcement.
Architect’s designs for new homes and extensions often have walls of glass, huge bi-fold doors and glass corners – but these are not always possible structurally or will need significant reinforcement that will add significant cost to ensure the lateral stability of the structure.
If you are having an extension, thinking of bi-fold doors, or are working on new build plans, speak to a structural engineer early on, before you apply for planning permission, because you might find that the plans are approved, when you come to build them are either not achievable or need costly strengthening works. Give SWJ Consulting a call on 01993 225085 or email if you’re working on a residential project, either a new build or an extension and we can have a no-obligation chat.
