Herts Structural Design - 07838 258421
Homeowner Advice
1. Always Consider Foundations
When planning an extension, always consider foundations, not just aesthetics or layout. Decisions made at this stage can have a large impact on cost, schedule, and structural safety. Without solid foundations, everything else fails.
Foundations: Soil and Trees Matter
The type of soil beneath your property is a critical factor. Clay, sand, gravel, or made-up ground behave very differently under load.
Nearby trees significantly influence foundation design if foundations are founded in clay.
For example:
· An oak tree near a house founded on clay likely requires piles and ground beams, not a standard strip footing.
· Failing to account for root-induced soil movement can lead to cracking, subsidence, and costly, disruptive remediation.
Common Mistake:
Assuming a 1-meter-deep footing is sufficient for a typical semi-detached house extension. This can result in:
· Construction delays
· Large additional expenditure
· Potential structural problems
Key Principle:
Every extension must be designed with site-specific foundations. Early consultation with a structural engineer prevents errors, saves money, and ensures long-term safety.
2. Removing a Load-Bearing Wall
When planning an extension or internal alteration, removing a significant masonry load-bearing wall is one of the most critical decisions. This is not just about creating an open space — it involves real structural engineering to keep your house safe.
Why a Steel Frame is Often Required
A steel frame is not "overdesign"; it serves several essential purposes:
• Lateral Stability – Maintains the structure’s ability to resist horizontal forces, such as wind, and retains stability that was originally provided by the wall.
• Deflection Control – Prevents excessive sagging or bending under load, which could crack ceilings, floors, or walls. Also, large runs of bi-fold doors are highly susceptible to vertical deflection. Bi-fold door manufacturers often require deflection restricted to 5mm.
• Prevention of Overload at Masonry Bearings – Ensures existing brickwork or blockwork is not subjected to stress beyond its capacity.
• Prevention of Overload of Existing Foundations – Distributes new loads safely so the foundations under beam bearings are not overstressed.
Key Principle:
The design of any steel frame must consider house stability, new & existing loads, wall strength, span, and foundation capacity. Assumptions or “rules of thumb” from builders without structural engineering input can lead to costly, unsafe mistakes.
3. When Builders Say "Overdesigned"
When a builder simply says a structure is “overdesigned,” it can leave homeowners confused and worried—but the term alone isn’t helpful. A builder should ask specific questions, such as why a portal frame has been used in a certain location, or whether a simply supported beam on padstones might work instead. This allows the structural engineer to explain the reasoning in plain language, covering important factors like lateral stability, load distribution at bearings, and deflection control. Homeowners benefit when engineers and builders communicate clearly, ensuring safety without unnecessary complexity.
4. Always Check Whether Public Sewers Cross Your Property
Public sewers can require a Building Over Notice Application and special foundation arrangements to bridge the sewer leaving a clearance zone between the foundations and the public sewer. This can be quite challenging to achieve if the site is small and access is restricted.
5. Don't Forget A Party Wall Notice
If your project requires work on the wall between your property and next door, a Party Wall Notice will need to be served on your Neighbour.
If your project requires a new foundation within 3m of your neighbour's house, a Party Wall Notice will need to be served on your Neighbour.