Index: binaries/data/mods/public/simulation/ai/common-api/entity.js
===================================================================
--- binaries/data/mods/public/simulation/ai/common-api/entity.js
+++ binaries/data/mods/public/simulation/ai/common-api/entity.js
@@ -50,8 +50,10 @@
 
 	"matchLimit": function() {
 		if (!this.get("TrainingRestrictions"))
-			return undefined;
-		return this.get("TrainingRestrictions/MatchLimit");
+			return this.get("TrainingRestrictions/MatchLimit");
+		if (!this.get("BuildRestrictions"))
+			return this.get("BuildRestrictions/MatchLimit");
+		return undefined;
 	},
 
 	"classes": function() {
@@ -454,7 +456,10 @@
 
 	"walkSpeed": function() { return +this.get("UnitMotion/WalkSpeed"); },
 
-	"trainingCategory": function() { return this.get("TrainingRestrictions/Category"); },
+	"limitCategory": function() {
+		return this.get("TrainingRestrictions/Category") ||
+			this.get("BuildRestrictions/Category");
+	},
 
 	"buildTime": function(productionQueue) {
 		let time = +this.get("Cost/BuildTime");
@@ -463,8 +468,6 @@
 		return time;
 	},
 
-	"buildCategory": function() { return this.get("BuildRestrictions/Category"); },
-
 	"buildDistance": function() {
 		let distance = this.get("BuildRestrictions/Distance");
 		if (!distance)
Index: binaries/data/mods/public/simulation/ai/common-api/filters.js
===================================================================
--- binaries/data/mods/public/simulation/ai/common-api/filters.js
+++ binaries/data/mods/public/simulation/ai/common-api/filters.js
@@ -77,6 +77,11 @@
 		"dynamicProperties": []
 	}),
 
+	"byBuildableEntities": (civ) => ({
+		"func": ent => ent.buildableEntities(civ),
+		"dynamicProperties": []
+	}),
+
 	"byCanAttackClass": aClass => ({
 		"func": ent => ent.canAttackClass(aClass),
 		"dynamicProperties": []
Index: binaries/data/mods/public/simulation/ai/common-api/gamestate.js
===================================================================
--- binaries/data/mods/public/simulation/ai/common-api/gamestate.js
+++ binaries/data/mods/public/simulation/ai/common-api/gamestate.js
@@ -587,6 +587,11 @@
 	return this.updatingGlobalCollection("player-" + this.player + "-research-facilities", m.Filters.byResearchAvailable(this, this.playerData.civ), this.getOwnEntities());
 };
 
+m.GameState.prototype.getOwnBuilders = function()
+{
+	return this.updatingGlobalCollection("player-" + this.player + "-builders", m.Filters.byBuildableEntities(this.playerData.civ), this.getOwnEntities());
+};
+
 
 m.GameState.prototype.countEntitiesByType = function(type, maintain)
 {
@@ -700,45 +705,57 @@
 };
 
 /** This returns only units from buildings. */
-m.GameState.prototype.findTrainableUnits = function(classes, anticlasses)
+m.GameState.prototype.findCreatableEntities = function(unit, classes, anticlasses)
 {
-	let allTrainable = [];
+	let allCreatable = [];
 	let civ = this.playerData.civ;
-	this.getOwnTrainingFacilities().forEach(function(ent) {
-		let trainable = ent.trainableEntities(civ);
-		if (!trainable)
+	(unit ? this.getOwnTrainingFacilities() : this.getOwnBuilders()).forEach(function(ent) {
+		let creatable = unit ? ent.trainableEntities(civ) : ent.buildableEntities(civ);
+		if (!creatable)
 			return;
-		for (let unit of trainable)
-			if (allTrainable.indexOf(unit) === -1)
-				allTrainable.push(unit);
+		for (let entity of creatable)
+			if (allCreatable.indexOf(entity) === -1)
+				allCreatable.push(entity);
 	});
 	let ret = [];
 	let limits = this.getEntityLimits();
 	let current = this.getEntityCounts();
 	let matchCounts = this.getEntityMatchCounts();
-	for (let trainable of allTrainable)
+	for (let creatable of allCreatable)
 	{
-		if (this.isTemplateDisabled(trainable))
+		if (this.isTemplateDisabled(creatable))
 			continue;
-		let template = this.getTemplate(trainable);
+		let template = this.getTemplate(creatable);
 		if (!template || !template.available(this))
 			continue;
 		let limit = template.matchLimit();
-		if (matchCounts && limit && matchCounts[trainable] >= limit)
+		if (matchCounts && limit && matchCounts[creatable] >= limit)
 			continue;
 		if (classes.some(c => !template.hasClass(c)))
 			continue;
 		if (anticlasses.some(c => template.hasClass(c)))
 			continue;
-		let category = template.trainingCategory();
+		let category = template.limitCategory();
 		if (category && limits[category] && current[category] >= limits[category])
 			continue;
 
-		ret.push([trainable, template]);
+		ret.push([creatable, template]);
 	}
 	return ret;
 };
 
+/** This returns only units from buildings. */
+m.GameState.prototype.findTrainableUnits = function(classes, anticlasses)
+{
+	return this.findCreatableEntities(true, classes, anticlasses);
+};
+
+/** This returns only structures from units. */
+m.GameState.prototype.findBuildableStructures = function(classes, anticlasses)
+{
+	return this.findCreatableEntities(false, classes, anticlasses);
+};
+
 /**
  * Return all techs which can currently be researched
  * Does not factor cost.
Index: binaries/data/mods/public/simulation/ai/petra/headquarters.js
===================================================================
--- binaries/data/mods/public/simulation/ai/petra/headquarters.js
+++ binaries/data/mods/public/simulation/ai/petra/headquarters.js
@@ -2216,7 +2216,7 @@
 
 	// build limits
 	let limits = gameState.getEntityLimits();
-	let category = template.buildCategory();
+	let category = template.limitCategory();
 	if (category && limits[category] !== undefined && gameState.getEntityCounts()[category] >= limits[category])
 	{
 		this.buildManager.setUnbuildable(gameState, type, 90, "limit");
Index: binaries/data/mods/public/simulation/ai/petra/navalManager.js
===================================================================
--- binaries/data/mods/public/simulation/ai/petra/navalManager.js
+++ binaries/data/mods/public/simulation/ai/petra/navalManager.js
@@ -791,7 +791,7 @@
 		if (!template.available(gameState))
 			continue;
 
-		let category = template.trainingCategory();
+		let category = template.limitCategory();
 		if (category && limits[category] && current[category] >= limits[category])
 			continue;