I was looking for some advice and help really. I'm looking at doing an extension on my house at the back going off the garage. Basically I'm on a really tight budget and need to save money where i can i already have the garage converted into a gym and have put damp proof membrane on the walls and floors underneath the batons Ive used on the wall Ive got some damp coming through on one corner and was wondering is there anyway to apply a damp course onto a sectional garage ? Also another question when i build the extension I'm looking at building level with the garage wall and building over the garage would i need to tie it into the garage if so how ? Thanks in advance Attached an image of the extension i plan on doing onto the garage so you get the general idea of what i mean.