# Do we allow mass and moment of the footing itself, when calculating ground support and eccentricity of a footing?

Suppose we are designing a footing for the wall of a building. There are two checks that are crucial.

• Ground support: suppose the ground is assessed as being suitable to load up to 80 kN/m2. Then a wall that places a line load of 40 kN/m on the footing, needs a footing 500mm wide at minimum.
• Eccentricity: Suppose in the above example, the footing is closed to one side than the other. Then the pressure on one side could still be more than ground support can be relied upon, even if the footing is over 500mm wide. The pressure at both edges must be under 80 kN/m2, not just the average pressure under that value.

But there are a further 2 possible factors to consider.

• Footing's self-weight: The footing itself could have significant mass, and will usually be denser than the supporting subsoil, shouldn't it be included in the overall load? and
• Stabilising effect of footing itself: its own considerable mass will tend to stabilise it (by adding a substantial additional moment to the eccentricity check and therefore, although it increases total ground pressure, it also reduces ground support pressure difference across the footing), and reduce overall eccentricity.

Do we take those into effect? I've never seen it done on an ordinary house wall or similar scale structure, so is it wrong to do so, or just insignificant, or a problem?

Note: UK construction norms being considered if that matters

• I donot belong to Civil Engineering community but from Aerospace community, but while calculating any kind of loads acting on the structure, we usually go for the most crucial ones. By this, I mean that we might include the mass/moment due to aircraft structure itself in the overall loads, if it might result in that structure being subjected to higher stresses/displacements. If not, then we don't include it. It depends how you reckon will effect the overall loadings (and hence the stresses/displacements) of the structure if you include them or not. Feb 20, 2022 at 14:21
• For something like this, there will be standard practices. Perhaps because some factors are allowed for already in other figures. I can imagine aerospace, everything structural on a new design is checked in a much more in depth way, from discrete finite analysis through to first principles. Not so for ordinary mundane construction on this scale, there will be usual norms what's checked,what is allowed for on other ways - a lot of norms and simplifications of how loads work and what performances to assume, in the analysis. Feb 20, 2022 at 14:39
• If you talk about standard practices, then I don't think you couldn't find anything on the internet itself (except for this site). Feb 20, 2022 at 15:55