Attaching a Lean-To Porch to the side of a House

[DaveC426913]

TL;DR Summary

Do I need two nailing boards to attach this trussed roof to my house?

I'm planning to tear down the old metal gazebo over the patio and build build a porch roof over the side door. It's a sliding door that is raised 18" above the patio, so its total height is about 8½ feet.

I figure a nice trussed structure will be sturdy enough, especially since it sticks out 12 feet. I believe our local codes require at least a 4:1 slope.

I've never attached a structure to a house before; I've always avoided that by building free-standing structures. So I'm not 100% sure how to attach it.

I need a nailing board which is bolted and glued to the brick face of my house. That'll serve to attach the roof face. Is it common to attach a second nailing board just above the door? I mean it looks pretty obviously like I have to, I just haven't come across a lot pf plans showing this.

(TBH, it wasn't my intention to have the porch ceiling 8½ feet up, but the height of the door means it has to be, unless I make some weird design change.

 

[Lnewqban]

Trusses should hang from the bottom horizontal member, never from the web or top member, as per manufacturer's instructions.

Then, they should be strapped to the supporting ledge (for wind load uplift), which should be bolted to the brick wall (preferably with all-way-through bolts and nuts).

These techniques are for decks, but some of them could apply to trusses:

https://www.jlconline.com/deck-builder/dropping-the-deck-ledger_o

https://www.jlconline.com/deck-builder/joist-hangers-for-decks_o

https://www.jlconline.com/deck-builder/installing-a-deck-ledger_o

https://www.jlconline.com/deck-builder/installing-a-deck-ledger-part-2_o

 

[DaveC426913]

OK, this is concerning, because what you're saying makes no sense to me.

Trusses should hang from the bottom horizontal member, never from the web or top member, as per manufacturer's instructions.

How can trusses hang from the bottom member? I can't even picture that.

This is similar to what I'm planning to build:

I don't know what parts of this might or might not apply.

These techniques are for decks, but some of them could apply to trusses:

https://www.jlconline.com/deck-builder/dropping-the-deck-ledger_o

https://www.jlconline.com/deck-builder/joist-hangers-for-decks_o

https://www.jlconline.com/deck-builder/installing-a-deck-ledger_o

https://www.jlconline.com/deck-builder/installing-a-deck-ledger-part-2_o

 

[berkeman]

Have you asked your local building department? They can probably answer your question pretty quickly.

And while you are there, you can ask if you need to pull a permit for the construction, since it involves adding a load to a load-bearing exterior wall. Is snow load an issue where you live?

Looks like a fun project.

This is similar to what I'm planning to build:

What keeps that from racking in the front-back axis (my front-back as I look from the vantage point of that picture)? It seems like some sturdier support posts and some triangle bracing near the top of those posts would help a lot to resist racking in that axis...

 

[DaveC426913]

What keeps that from racking in the front-back axis (my front-back as I look from the vantage point of that picture)?

Oh, I'm gonna put some cross-bracing in.

It's just the attachment to the wall I'm concerned about, really. The picture I included is just something I grabbed to show lnewqban what my intended design is, truss-wise.

 

[jrmichler]

The attachment of the trusses to the wall must tie the trusses directly into the wall studs. If the trusses align with the studs, you MIGHT be able to use concealed flange joist hangers. Otherwise, you will probably need to install ledgers lag bolted to the wall studs, then support the trusses with joist hangers. The trusses will need to be supported at both top and bottom so as to positively prevent them from flopping over. This is a detail that needs to be discussed with your building inspector.

Concealed flange joist hanger:

The JLC articles linked in Post #2 are all good reading. There is more than one way to support a deck. Your lean to roof has similar loads as a deck of similar size, so the solutions are similar. With the exception that you do not have a rim joist to fasten to.

Something to keep in mind is that it's obvious that the trusses need to be supported against snow loads. It's not so obvious that design wind loads are greater than the weight of the roof, so the trusses also need to supported against wind loads trying to lift the entire roof up.

 

[DaveC426913]

The attachment of the trusses to the wall must tie the trusses directly into the wall studs.

Thats going to be tricky through brick.

I shoulda mentioned that up front. In Canada, not a lot of houses are made of anything except brick, so I kinda forgot that that is not taken for granted south of the border.

The trusses will need to be supported at both top and bottom so as to positively prevent them from flopping over.

Without a doubt. Thats the very thing Im highlighting in my opening post. A nailing board at top and bottom, which apparently is also called a ledger board.

 

[jrmichler]

I assume that the brick is a facade, with a load bearing wall behind the brick. If that is the case, then you would need to remove the brick behind the new trusses to attach directly to the load bearing wall underneath.

If you use ledger boards, remember that those boards support the entire roof, so they need to be attached with more than just a few nails.

This is a detail that needs to be discussed with your building inspector.

Need to reword: These are details that need to be discussed in detail with your building inspector.

Semi relevant anecdote: A nearby house had the back deck collapse last winter. The cause was a heavy buildup of snow sliding off the newly installed metal roof causing an impact load that tore the deck off. The tenant had warned the landlord, but some people have to learn the hard way.

 

[DaveC426913]

I assume that the brick is a facade, with a load bearing wall behind the brick. If that is the case, then you would need to remove the brick behind the new trusses to attach directly to the load bearing wall underneath.

I don't know if this is the way it's usually done. I see plenty of lean-to roofs attached without having to remove the brick.

If you use ledger boards, remember that those boards support the entire roof, so they need to be attached with more than just a few nails.

Yes. I've seen it called a nailing board from some bizarre reason, but of course it would be secured using concrete screws placed every couple of feet.

 

[gmax137]

And while you are there, you can ask if you need to pull a permit for the construction, since it involves adding a load to a load-bearing exterior wall.

Permit requirements vary from jurisdiction to jurisdiction. Where I live, this would definitely be "permit required."

People doing mods on their homes sometimes ignore the permitting, but this often ends badly. Even if the construction is robust and doesn't fail, even if it actually meets code, there can be trouble when they try to sell the house. I knew someone who had a bunch of plumbing work done off the books; when they went to sell the house the buyer's inspector wanted to see the permits. Sale contract cancelled. Town inspector made them cut open the walls so he could sign off on the plumbing.

I've seen it called a nailing board from some bizarre reason,

I think that's because the joists are "nailed" into the board, which is attached to the wall. When I was a laborer 50 years ago, we didn't have the metal joist hangers; the joists were "toenailed" into the board.

 

[DaveC426913]

People doing mods on their homes sometimes ignore the permitting, but this often ends badly. Even if the construction is robust and doesn't fail, even if it actually meets code, there can be trouble when they try to sell the house.

Indeed. I bought this house just 3 months ago and it has a huge 360 square foot enclosed sunroom (used as a plant nursery) off the back that is definitely, visibly not to code in so many ways.

I can see by Google that it has only been up for one winter so far, and the roof is made merely of transparent, corrugated panels that have a very low slope - 1:10 at best. We are about to see how it survives this first winter.

It does seem to have good bones though. The plan is to revisit it in the spring and raise the slope, replacing wonky rafters in the process.

We had an inspection that flagged it, along with a little electrical DIY - so we have our hands full remediating.

 

[DaveC426913]

I assume that the brick is a facade, with a load bearing wall behind the brick. If that is the case, then you would need to remove the brick behind the new trusses to attach directly to the load bearing wall underneath.

I don't know if this is the way it's usually done. I see plenty of lean-to roofs attached without having to remove the brick.

I humbly stand corrected, and you vindicated.

My local construction contractor cum lumber expert said the regulations now require joining through the brick to the joists - even removing brick if necessary.

He did suggest that - were I to put 6x6 posts down against the wall - it would obviate the need for the ledgers to take the load.

So basically, I'm making a self-supporting structure that happens to stand close enough to (and steadied by) the wall of my house that flashing will keep it water proof.

And that I am much more comfortable with.

I'm also gonna see about a ballpark quote for premade trusses built to my specs. (When I built my free-standing 12x20 porch a few years ago, it was the 13 trusses that were the heavy labour.)

 

[berkeman]

So basically, I'm making a self-supporting structure that happens to stand close enough to (and steadied by) the wall of my house that flashing will keep it water proof.

Great!

 

[jedishrfu]

Don't forget the termites! They can travel up the exterior post to get into your home unlikely but not impossible.

I know inspectors here look for places where there a joint and declare thats a possible termite entry.

 

[Nik_2213]

Also, differential settlement of main building and 'lean-to' footings. Consider issues of water-table changes due to shelter, seasonal heave and shrinkage, future repairs to post bases etc etc. And, yes, possibility of 'exceptional' weather, be it a storm-cell's violent down-draught, or knee-deep wet snow arriving overnight...
As mentioned above, please check building codes lest survey condemns your work to demolition...

FWIW, have you made provision for eg IP65-grade lighting and power outlet ??

 

[DaveC426913]

Also, differential settlement of main building and 'lean-to' footings. Consider issues of water-table changes due to shelter, seasonal heave and shrinkage,

Indeed. There is an underground river that runs right behind my house. It affects how the next row of houses are built.

And (we discovered upon receiving the key) there is a 10 foot 'no-go' zone* along our back fence that parallels the river.

* I forget what it's called. A City Encroachment? It's an area where we are not allowed to build on because there are underground structures - probably a drainage culvert.

 

[Spinnor]

I built a porch roof similar to your specs. I was able to tie in the house side directly to the end of the existing roof. 2x6 roof joists were sufficient for my span. You might need 2x8's considering your span and snow load. I finished the underside of the joists with vinyl soffit material. A beam supported by 3 posts holds up the other end. Seems like trusses are additional work and cost. A ledger beam attached through the brick into framing members or better yet the 2nd floor rim joist if possible should be plenty strong, the brick supports the vertical load and the framing members of the house the pull out forces which should not be that great. We had to make a simple sketch of the design and submit to the local code department along with a small fee.

See, Google search, "attaching a joist ledger board to side of my house through brick for a porch roof"

https://www.google.com/search?q=att...PXAZfGfD8rtiLMP97G_uAw&bih=486&biw=1093&hl=en

 

[DaveC426913]

A ledger beam attached through the brick into framing members or better yet the 2nd floor rim joist if possible

Aye, well, there's the rub.

Blowing through the brick to the frame is the big headache.

 

[Nik_2213]

Covert water-courses may be problematic...

An uncle told how, about 150 metres along from his house, there was a long-empty plot. No-one could remember why. Finally, got built on. New property promptly suffered from building damp, soggy garden, soggy lawn etc etc....
Much expensive investigation plus belated consultation of 1903 map showed a 'winterburn', literally a seasonal stream, ran through plot. New foundations acted like a weir, raising water-table. Owners & builders eventually split cost for a culvert / land-drain to be burrowed under house...

( IIRC, was arguably builders' fault, but parties 'settled out of court' lest their lawyers became rich...)

Near here, we have an ancient water-course, the River Alt, which drains our dry-foot sandstone ridge North-West across lowlands to sea-weir. To say it takes the scenic route understates its 'excursion'. Parts are open, parts culverted, parts fed by small, tributaries, parts diverted / canalised, with some parts sorta-co-opted into local parks etc. Other than a few linear-greens and 'no-builds', some parts appear 'lost'.....

 

[Spinnor]

Aye, well, there's the rub.

Blowing through the brick to the frame is the big headache.

You only should need max 1/2 inch holes which a hammer drill will do effortlessly through brick. If you look at the link I included going through brick is shown and only small holes are made. If the brick would need to be removed that would be a deal breaker for me. Your friendly local code enforcers may be willing to talk and would hopefully point you towards best practices in your area.

 

[DaveC426913]

You only should need max 1/2 inch holes which a hammer drill will do effortlessly through brick. If you look at the link I included going through brick is shown and only small holes are made. If the brick would need to be removed that would be a deal breaker for me. Your friendly local code enforcers may be willing to talk and would hopefully point you towards best practices in your area.

And how then does one secure to the frame? From the outside? Or the inside?

 

[Spinnor]

And how then does one secure to the frame? From the outside? Or the inside?

All the work should be able to be done outside of the house. If you were lucky enough to shoot for the rim joist that is a large target, house studs a smaller target. The links show work from the outside. Do some research and then talk to your inspector he could potentially save you a bunch of time and money. Looking at the instructions from a shingle bag asphalt shingles can be installed on a roof with a minimum 2 in 12 pitch so you might get away with a roof pitched as little as 3 in 12 with a safety factor.

The Canada building code is available for free,

https://nrc-publications.canada.ca/eng/view/object/?id=515340b5-f4e0-4798-be69-692e4ec423e8