New roof for detached masonry garage

[CactusInaHat]

Hi everyone, this coming spring I'm planning on building a new flat roof on our single car detached brick garage.

The garage is ~12'x24' double wythe red brick construction from what we think is the early 40s. The old roof was allowed to deteriorate beyond repair before we purchased the home; we demolished it last fall. The original roof was 2x6 joists placed in masonry pockets spaced 24"oc running the width of the garage with 1x6 plank decking and a asphalt roof. The joists span 11' 6".

My dilemma is whether or not to reuse the old masonry pockets for the new roof. I would obviously upsize the joists to 2x10 at 24"oc. However, I'd prefer to have the joists spaced 16"oc to prevent flat spots from forming on the low pitched roof. The way I've thought this is possible is to forego the masonry pockets and to use two 2x10 "ledgers" that run the length of the garage and then to use 2x8" joists spaced 16"oc. This was initially suggested to me by a structural engineer who was at my home for something else.

What I'm unsure of is how I would go about attaching the two ledgers to the brick walls. The two solutions I've thought of are to either A) drill through the walls and attach the ledgers with threaded rods and a plate on the exterior wall. Or, B) use some type of sleeve anchor such as redheads. My thinking in using the sleeve anchor is both sides of the roof are supported by structural walls so there should be minimal tension forces on the anchors.

Please advise!

 

[oldbutnotdead]

This is a UK site so things have different names..... depends how good your brickwork is. Sleeve bolts (redheads?) if your brickwork is in good condition, resin anchors if it is a bit flaky. Studs through the walls would need some sort of spreader on the outside, risk of corrosion, all a bit irritating really.

And the strength of the structure relies on the fact that once you have your joists fixed between the ledgers then the ledgers can't move away from the wall (the joists are in the way) and they can't move down the wall (the sleeve bolts or resin anchors prevent that) so the whole lot stays still. Happy days.

 

[CactusInaHat]

I'm sorry about any jargon I may be using. Redheads as in 3-5" sleeve bolts such as: http://www.homedepot.com/p/Red-Head...-Head-Sleeve-Anchors-25-Pack-11285/100201816.

The brickwork is quite solid, I've worked on the structure itself a bit, re-pointing and replacing some bricks, the bricks are quite solid. I wouldn't describe any of it as flaky.[/url]

 

[oldbutnotdead]

In that case crack on with the sleeve bolts- (can't see the Home Depot pages from here boo) just be careful about how deep into the wall you drill.....

 

[CactusInaHat]

I was leaning towards a longer sleeve bolt (like 5") however would you say it'd be better advised to keep it under half the width of the wall to avoid cracking?

 

[oldbutnotdead]

Your thinking is correct (longer sleeve= less chance of cracks forming). I was thinking half brick (single thickness) brick walls- by the sound of it yours are full-brick (2 bricks thick) so 5 inch sleeves will be fine