Use building blocks to produce models of pupils' designs, which they can describe and measure.
Do the same as above, looking at properties of shapes, use of mathematical language to describe shapes, use of appropriate units, consideration of accuracy, and use of coordinates to help produce the drawings. Logo could be used.
Extend the above activity to consider area and volume and more complex designs. Materials and construction costs could also be considered.
Asking students to produce scale drawings of plans for their designs is a worthwhile activity as it can be done at varying levels of sophistication.
These plans could be used to make scale models, moving from 2D to 3D.
The construction of a house is a good task to plan using critical path analysis, which forms part of the Decision Mathematics strand in ASA-level maths. Use CPA to plan the building of a simple prefabricated house or shed. CPA is widely used in construction.