I have an existing garage of about 7x4m, built of rendered single skin brick on about 12" reinforced concrete. The concrete slab extends well beyond the garage all around it by several metres. I want to build an extension on the end wall of the garage, with an internal door linking the two areas. It will have a flat felted roof and look a bit like a lean-to structure, about 3x4m footprint.
1. I'll be using concrete blocks to build the three walls. Can I mortar these straight on the existing slab or do I need to prep the slab surface somehow or tie them in to it? One concern is making sure no water can get under the blocks. I'll add a DPM a couple of courses up.
2. How should I tie the blockwork to the rendered end of the garage? Should I even tie it in at all or would I be better off with a flexible joint instead so it's effectively a three walled separate structure? I don't want to risk compromising the render and causing problems down the line.
Thanks.
1. I'll be using concrete blocks to build the three walls. Can I mortar these straight on the existing slab or do I need to prep the slab surface somehow or tie them in to it? One concern is making sure no water can get under the blocks. I'll add a DPM a couple of courses up.
2. How should I tie the blockwork to the rendered end of the garage? Should I even tie it in at all or would I be better off with a flexible joint instead so it's effectively a three walled separate structure? I don't want to risk compromising the render and causing problems down the line.
Thanks.
