A wall presses on whatever is beneath it as a load spread along its length, so its load is measured per metre. The self-weight line load is the wall height times its thickness times the material unit weight. A 3 metre high, 200 mm concrete wall carries about 15 kN per metre. If the wall also supports a floor, you add that on top. StructLoads models walls as line supports carrying this distributed load, and the calculation is short.
Self-weight per metre
A wall’s self-weight is a structural load you get from geometry and density. Per metre of wall length, it is the height times the thickness times the material unit weight. The height and thickness are in metres, the unit weight in kN per cubic metre, and the result is a line load in kN per metre. That is the load the wall delivers to the beam or footing beneath it from its own weight alone.
Material unit weights
The unit weight depends on what the wall is made of.
| Wall material | Unit weight (kN/m3) | 3 m x 200 mm line load |
|---|---|---|
| Reinforced concrete | 25 | 15.0 kN/m |
| Brick masonry | 18 to 20 | about 11 to 12 kN/m |
| Dense concrete block | 14 to 20 | about 8 to 12 kN/m |
| Lightweight partition | quoted per m2 | often 1 to 2 kN/m |
For masonry and blockwork, use the unit weight for the actual block and any render. The spread across brick types is real: Engineering ToolBox’s brick densities table runs from about 1765 kg per cubic metre for red facings to 2165 for engineering brick, roughly 17 to 21 kN per cubic metre before mortar, which is why the actual build-up beats a single generic figure. Lightweight stud partitions are usually quoted directly as a load per square metre of wall, which you multiply by the height to get the line load.
A worked example
Take a 3 metre high, 200 mm thick reinforced concrete wall. Its self-weight line load is 3 times 0.2 times 25, which is 15 kN per metre. A 2.6 metre high, 140 mm brick wall at 19 kN per cubic metre gives 2.6 times 0.14 times 19, which is about 6.9 kN per metre. The taller, thicker, denser the wall, the larger the line load, and the relationship is linear in each of the three inputs.
Adding the floor the wall carries
A load-bearing wall carries more than itself. If it supports a floor, add the floor load over the wall’s tributary width, the half spacing to the parallel support on each side, exactly as for a beam. A wall with a 2.5 metre tributary width under a 5 kN per square metre floor adds 12.5 kN per metre to its self-weight. The full accumulation, including load from a wall above, is set out in bearing wall load takedown.
Dead, live and where it goes
The wall self-weight is permanent, so it is dead load; a fixed partition is dead, a movable one is usually a live allowance. Any floor load the wall carries keeps its own dead and live split as it passes through. The combined line load then goes to a strip footing or a supporting beam, and the wall’s concrete self-weight relates to the slab figure in concrete slab self-weight calculation.
Key takeaways: wall line load
A wall’s self-weight line load is height times thickness times unit weight, in kN per metre: about 15 for a 3 metre by 200 mm concrete wall. Add the tributary floor load if the wall is load-bearing, and keep the dead and live split. StructLoads carries the wall line load down as a preliminary figure a qualified engineer confirms.
Quick answers
How do you calculate a wall line load?
Multiply the wall height by its thickness by the material unit weight to get the self-weight per metre of length. A 3 metre high, 200 mm concrete wall at 25 kN per cubic metre carries 3 times 0.2 times 25, which is 15 kN per metre. If the wall also supports a floor, add the floor load over the wall’s tributary width to get the total line load.
What is the unit weight of a wall?
It depends on the material. Reinforced concrete is about 25 kN per cubic metre, brick masonry around 18 to 20, dense concrete block around 14 to 20, and lightweight stud-and-board partitions much less, often quoted directly as a few tenths of a kN per square metre of wall. Use the unit weight for the actual wall build-up.
Is a wall line load a dead load or a live load?
A wall’s own self-weight is a permanent dead load, counted by its real weight per metre. If the wall is a fixed, permanent partition it is dead load; if it is movable, it is usually covered by a live-load partition allowance instead. Any floor load the wall carries keeps its own dead and live split as it passes through.
When is a wall line load not just self-weight?
It is not just self-weight whenever the wall also supports a floor or roof, or carries load from a wall above. Then the line load is the self-weight plus the tributary floor load plus the load from above. A wall that only encloses space carries just its self-weight; a load-bearing wall carries much more.