attaching pergola to wall

[charlieboy]

I would like to build a lean-to pergola attached to my house wall. What is the best way to attach the (sloping) rafters to the wall plate (ledger board). Common practice seems to be to use joist hangers, but I thought a prettier solution would be to notch the rafters into the wall plate. Would screwing/nailing the notched rafter from above into the (2" thick?) wall plate be secure enough or is there a better way to achieve this without using joist hangers?

 

[Sachakins]

I would like to build a lean-to pergola attached to my house wall. What is the best way to attach the (sloping) rafters to the wall plate (ledger board). Common practice seems to be to use joist hangers, but I thought a prettier solution would be to notch the rafters into the wall plate. Would screwing/nailing the notched rafter from above into the (2" thick?) wall plate be secure enough or is there a better way to achieve this without using joist hangers?

Tight joints, waterproof glue, clamp and screw. If you wanted pretty and super secure, you could use a dovetail joint rather than notch and screw.
Other option would be to screw joists from back of ledger board, then mount the lot to your wall, seen it done a couple of times, but real faffing about for little gain IMHO.

 

[smackie]

Got a similar project soon with a lean-to covered area in the garden. The plan is to notch the wall plate to allow the rafters to sit in it. I’m planning to notch the rafters with an inset 90 degree cut so that the bottom of the rafter slot is level. The front beam on the lean-to will also be slightly notched to allow the rafter to sit down into it a bit. Joists will be fixed from the top (which is okay for me as the lean-to is going to be slated.

This is pretty much what they used to do before joist hangers.

Agree with @Sachakins - you can fix them from the back of the ledger board but it’s really unwieldy on anything other than the smallest constructions.

 

[Richard_C]

I built a simple pergola twixt house and garage wall a good few years ago. One design consideration was the slats had to be removable so I could get to the gutters and window frames above for maintenance.

Upside-down joist hangers aren't as nice as a proper job but you can easily take out a single side locating screw and lift out individual rafters to get a ladder up. Maybe you don't need to, and if you slate it you won't be able to, but worth a think.

(My neighbour has a really nice part covered pergola over his patio, in the "L" of an L shaoped house. He's now having a "doh" moment because the gutter is blocked in the corner so it overflows and he can't woodstain 3 of his windows without a big dismantling project or expensive scaffold. I've suggested an abseiling harness and clipping on to some eyes but he's not keen)

 

[Cabinetman]

I built a simple pergola twixt house and garage wall a good few years ago. One design consideration was the slats had to be removable so I could get to the gutters and window frames above for maintenance.

Upside-down joist hangers aren't as nice as a proper job but you can easily take out a single side locating screw and lift out individual rafters to get a ladder up. Maybe you don't need to, and if you slate it you won't be able to, but worth a think.

(My neighbour has a really nice part covered pergola over his patio, in the "L" of an L shaoped house. He's now having a "doh" moment because the gutter is blocked in the corner so it overflows and he can't woodstain 3 of his windows without a big dismantling project or expensive scaffold. I've suggested an abseiling harness and clipping on to some eyes but he's not keen)

If your neighbour had it built properly, perhaps he could use it as scaffolding? Sling a few boards on it and away you go.

 

[LBCarpentry]

Dovetail notches would be best. Stop them sliding out and would be difficult to achieve.

Of course you’d have to mention it every time anyone paid even the slightest amount of interest.

Louis

 

[charlieboy]

Thanks guys for all your help/suggestions. I quite like the idea of the dovetailed notch (not only for the bragging rights!). I assume this would still need a screw from above to avoid any chance of the rafter lifting off? Would pre-drilling and a M8 or M10 coach screw (or bolt) be the best option? Also, would a 2" (44mm finished size?) thick wall plate give sufficient thickness a) to create a secure dovetail and b) to securely hold a screw/bolt - or would I need something thicker?

Thanks too for the reminder to think about maintenance considerations - in my case this would mainly be painting the fascia board above the pergola (it will be attached to a single storey flat roofed kitchen extension). The pergola will not be roofed - it will just be an open structure with a removable sail for shade, but I will need to check that the rafter spacing enables me to get between them to paint the fascia (or else make the rafters removable).

One other question, if I may - The pergola will be about 3m wide by 4m from wall to front posts. (The actual spans will be a little less as there will be some overhang beyond the posts). As it will not be roofed it will not need to bear any additional weight. What timber dimensions should I be using for these spans - for the a) 2 front posts, b) the front supporting beam, c) the wall plate and d) the rafters. I will probably be using ordinary treated softwood (or I may have an option on some Douglas fir at a similar price).