built with glacial erratics and rubble
...that before brick became available as a building material, churches in medieval Northern Europe were commonly built with glacial erratics and rubble?
...that before <a href="./Brick" id="mwEMY" rel="mw:WikiLink" title="Brick">brick</a> became available as a <a href="./Building_material" id="mwEMc" rel="mw:WikiLink" title="Building material">building material</a>, <a class="mw-redirect mw-disambig" href="./Churches" id="mwEMg" rel="mw:WikiLink" title="Churches">churches</a> in <a class="mw-redirect" href="./Medieval" id="mwEMk" rel="mw:WikiLink" title="Medieval">medieval</a> <a href="./Northern_Europe" id="mwEMo" rel="mw:WikiLink" title="Northern Europe">Northern Europe</a> were commonly <b id="mwEMs"><a href="./Fieldstone_church" id="mwEMw" rel="mw:WikiLink" title="Fieldstone church">built with glacial erratics and rubble</a></b>?