If you will start over,I suggest you to check your model often with the SuSolid plugin,and your model will be always "clean"

Hi Cotty. it was just a simple block model, the outline extruded and further extrusions to create the roof, so I just decided to place the window opes and noticed when removed the rectangles that the inner face of the block model was gone. I just thought it might be a quicker way to model rather than pulling up the external walls, it's not causing any grief I was just wondering is this usual with sketchup, thanks for your reply

Thanks Dave, top tip