Kubaka ibyubaka biramba kandi bihanitse cyane byubaka bishingiye cyane cyane muguhitamo inyongeramusaruro, bigira uruhare runini mukuzamura ibintu bifatika. Izi nyongeramusaruro, nk'ivu ry'isazi, cenosifera, kwaguka kwa perlite, microsperes idafite ikirahure, fibre beto, hamwe no kugabanya amazi, birahindura inganda zubaka zitezimbere ivangwa rya beto hamwe n’ibivangwa.