how to construct a lean to roof to a cement wall?

Question

I want to put a small addition to the side of my concrete bungalow. it will be shed with lean to roof I want to construct this without having to put columns/post on the side of the house what I want to do is attach like a piece of 2x4 or 1x4 to the wall horizontally and have my rafter attached to it. the excisting concrete wall is made of 6 inch thick cinder blocks

please help

Answer 1

Youve got the right idea, but your lumber selection is too small. If this is going to be "room sized"... that is, at least 10ft x 10ft, make the ledger board at least a 2x6, or 2x8. (I prefer the 2x8 myself). Use joist hangers to attach the lean-to rafters (also 2x6) to the ledger board. This is a lot stronger, and easier, than 'toe nailing' the rafters to the ledger.

You will want to anchor the ledger board to the cement block wall, oversized 'mollies', or tapcons will work just fine... put a little construction adhesive on the back side of the 2x too.

I like to use 6x6 posts, but if this addition isnt very large, 4x4's will work. Set them 2 feet into the ground with concete, minimal, to get below most frost lines. I like to run a top sill plate, with at least one 2x6 under it, attached to the posts, to support it. I make the sill plate wide enough to cover the post, and the sill ledger.

Notch the rafter joists to match the angle on the sill plate. and again, use some form of joist hanger, or hurricane tie. (the hurricane ties work well at this end of the rafter joist.

Next step depends on how you are going to roof the structure. If you are going to use sheetmetal roofing, then you will want to install some 1x material. I like to use 1x6, or 1x8 and split it on my table saw. (costs less than buying 1x3's). If you are going to shingle, then you need to sheathe it with 3/4 exterior grade plywood. If it is very large, use tongue and groove, or plywood clips. Cover with a good felt paper, install your drip edge, and apply shingles. (Run a row of shingles around the perimeter, and don't forget the flashing where the roof meets the wall)

Have Fun

(I'll add this here - If you are setting the posts on a concrete footer or slab, instead of in the ground, use a metal base. They can be found near the joist hangars, and such in any building supply store.)

Answer 2

You've already the answer/solution. A Ledger attached at the wall side, and some method of support at the outer edge of the roof.

Answer 3

If it were me, I'd attach the board to the cinder block wall with tapcon screws and then use joist hangers for the roof beams. I'd use at least a 2x4... I'd probably go with something bigger, but I also tend to over-build. :)