constructing buildings rts style.

currently i have a co routine that starts after i lock the position of the building prefab. this coroutine is attached to my builder unit which simulates or "fakes" constructing a building. i have a delegate that i pass to my gui system ; which on button click does the entire "action" of construction.

problem:

the coroutine keeps starting over and over again for some reason. (Final Placement Method).

Construction Script:

public class Construction : MonoBehaviour {

 public GameObject [] buildings;
 public Action.myActions constructingBarr;
 public Action.myActions constructingBase;
 public Color MatColor {
     get {
         return materialColour;
     }
     set {
         myRenderer.material.color 
         = value;
     }
 }
 public bool IsPlaced {
     get {
         return isPlaced;
     }
     set {
         isPlaced = value;
         if(isPlaced!=false) {
             StopCoroutine ("ConstructBuilding");
             StartCoroutine ("ConstructBuilding");
         }
     }
 }

 private bool isPlaced;
 private Builder myBuilder;
 private Color materialColour;
 private Renderer myRenderer;
 private MeshRenderer myMesh;
 private Transform currentBuilding;

 private void Start() {
     myBuilder = GetComponent <Builder> ();
     myMesh = GetComponentInChildren <MeshRenderer> ();
 }

 private void FetchRenderer() {
     try {
         myRenderer = currentBuilding.
             GetComponentInChildren<Renderer> ();
     }catch {};
 }

 private void Update() {
     LocatingBuildingPos ();
     Debug.Log (isPlaced);
 }

 private void SaveOrginalMatColour () {
     try{
         materialColour = 
             myRenderer.material.color;
     }catch {};
 }

 public bool InstantiateBuilding(GameObject building) {
     currentBuilding = ((GameObject)Instantiate
                        (building)).transform;
     FetchRenderer ();
     return IsPlaced = !true; 
 }

 public void CreateBase() {
     InstantiateBuilding (buildings [1]);
     SaveOrginalMatColour ();
 }

 public void CreateBarracks() {
     InstantiateBuilding (buildings [0]);
     SaveOrginalMatColour ();
 }

 public void LocatingBuildingPos() {
     if (!IsPlaced) {
         try {
             var cameraYPos = Camera.main.transform.
                 position.y;
             var mousePos = new Vector3
                 (Input.mousePosition.x,
                  Input.mousePosition.y,
                               cameraYPos);
             var mousePosWorld = 
             Camera.main.ScreenToWorldPoint (mousePos);
             currentBuilding.transform.position 
                 = new Vector3 (mousePosWorld.x, 0, 
                                mousePosWorld.z);
         }
         catch {};
     }
     FinalPlacement ();
 }

 IEnumerator ConstructBuilding () {
     Vector3 previousBuilderPos = transform.position;
     Vector3 buildingPos = currentBuilding.
             transform.position;
     SetConstructionTarget (buildingPos);
     yield return new WaitForSeconds (4f);
     IsNotConstructing (false);
     MatColor = Color.red;
     yield return new WaitForSeconds (4f);
     MatColor = Color.yellow;
     yield return new WaitForSeconds (8f);
     MatColor = Color.green;
     myBuilder.Target = previousBuilderPos;
     yield return new WaitForSeconds (3f);
     myRenderer.material.color = MatColor;
     IsNotConstructing (true);
     Debug.Log ("Construction Complete !");
 }

 public void IsNotConstructing(bool value) {
     myMesh.enabled = value;
     gameObject.collider.enabled = value;
     currentBuilding.collider.enabled = value;
 }

 public void SetConstructionTarget(Vector3 target) {
     myBuilder.Target = target;
 }

 public bool FinalPlacement () {
     if (Input.GetMouseButtonDown (0)) {
         return IsPlaced = !false;
     } else {
         return !IsPlaced;
     }
 }

 private void OnEnable() {
     constructingBarr += CreateBarracks;
     constructingBase += CreateBase;
     //constructingBarr += myEvent(buildings[1]);
     //constructingBase += myEvent(buildings[0]);
 }

 private void OnDisable() {
     constructingBarr -= CreateBarracks;
     constructingBase -= CreateBase;
     //constructingBarr -= myEvent(buildings[1]);
     //constructingBase -= myEvent(buildings[0]);
 }

}