help needed with joists when loft converting Re-generate an old or tired space and give it a fresh breath of life. Click here for answers, information and tips

[twixee]

hi there im wanting to convert my loft i am fairly confedent in doing this,however im lost when it comes to joists???
i have a loft of 7.5mtr x 4.8mtr but im pretty certain i have no load barring walls,will i need to add steal beams,how will this effect my extieror wallsd if so? can anyone help please?