This study explored the potential of using high-calcium grate ash and fly ash from wood combustion in combination with metakaolin and limestone as a replacement material for cement in low-clinker binders. Three products were investigated: sand mortars and lightweight mortars, as well as pellets in order to obtain lightweight, low-clinker, and waste-embedding aggregates. In mortars, the sulphur- and potassiumrich fly ash was found to be detrimental to the strength, even at low amounts (5%), whereas the grate ash could replace up to 15% of cement in a binder. This addition improved early age strength but rather acts as a filler at later age. Slaking the ash before blending was found not to be necessary, although it slightly improved mechanical performance. Lightweight mortars were explored by replacing sand with sawdust, another byproduct from the timber transformation chain. Low densities (of 900-1500 kg/m3) could be obtained, but it was also shown that these lightweight materials would be better suited for non-structural applications, such as thermal insulation. A batch of lightweight aggregates based on these mortars was produced through pelletizing, obtaining a material with properties close to that of low-grade expanded clay aggregates.