[Brother Antioch]

Hi, folks. New to the forum here, (made my brief introduction where appropriate) and have a question I'm hoping to get answered.

In a nutshell, I have a 41' park-model trailer on a lot in a park. I am going to be putting a roof over the entire thing, and also extending over the 40x12 deck I'm putting on it this summer. Total span will be around 24' x 42'. The problem is, I have to make sure the trailer can be removed and replaced, if necessary (and by park rules) so I can't do a simple ceiling joist or rafter/collar ties, as I wouldn't have the room to clear the roof-top AC and plumbing/furnace vents and chimney.

I'm thinking I can do a post and beam style roof, with a ridge beam in the centre. I'd be putting posts equidistant every 10' and change, and would use a triple 2x10 in an overlapping glued and screwed fashion. (10-10-10-10 then 5-10-10-10-5 and another 10-10-10-10 sections). Obviously the math is a little more precise, as I'm going 42' not 40', but you get the picture. I've included a quick diagram, so as to fully explain.

What I'm curious to is am I going overboard on the structure or am I cutting it too close to the bone? I've built a ton of decks over the years, but this will be "uncharted ground", so to speak. I'm sure I could get away with 24" centres, but I'm happy going 16. It's more about the ridge beam I'm curious. Snow loads here are around 35 PSF and the dead load shouldn't be too much, as it's simple 1x3 strapping on 24" centres with a metal roof.

So, in short (hahaha), does anyone have any thoughts on this?

Cheers,
BA.

 

[Nealtw]

You can't afford a 42 ft beam.

Vaulted trusses, lets talk height. How high it is an AC and how high are the outer beams. How far would the side of the AC be from the side posts?
Don't count the vents, they have to go thru the roof so they can be made shorter for moving.

 

[Nealtw]

like this

 

[Brother Antioch]

You can't afford a 42 ft beam.

Vaulted trusses, lets talk height. How high it is an AC and how high are the outer beams. How far would the side of the AC be from the side posts?
Don't count the vents, they have to go thru the roof so they can be made shorter for moving.

The outer beams will be 8' high, same as the roof line of the trailer. The centre beam will be 12' high, so a 4' height at the peak and flush at the bottom ends. The A/C, roof vents and vaulted ceiling would need approx. 2' clearance above, so 10' clearance.

I thought about scissor trusses, as one possible option. But you mention a 42' beam. What's wrong with laminating 10'6" 2x10's for 3 layers, offsetting the centre layer by 50%, and having each outer connection (at the 10'6 points) supported by a 6x6 post for 5 posts in total per beam? I could probably put either collar ties or plywood on either sides of the rafters for more rigidity. Wouldn't that be enough?

Edit:
Just wanted to say, thanks for the swift reply. I'm not tackling this project until the Spring, but want to get all my ducks in order so that I'm done it all in the first 2 weeks of May.

Cheers,

BA.

 

[Nealtw]

I was thinking one long beam down the center and not a row of posts. :wink2:
Engineers don't like laminated beams as such we to a post to post beam system with metal straps to tie them together, that might be different there.

The roof pitch goes up usually with snow load, your 4 /12 seems low and would call for taller rafters.

Unless you have height restrictions for total height, I like trusses because you have no centre posts and they are engineered so you have much less to guess about.

 

[Brother Antioch]

I was thinking one long beam down the center and not a row of posts. :wink2:
Engineers don't like laminated beams as such we to a post to post beam system with metal straps to tie them together, that might be different there.

The roof pitch goes up usually with snow load, your 4 /12 seems low and would call for taller rafters.

Unless you have height restrictions for total height, I like trusses because you have no centre posts and they are engineered so you have much less to guess about.

Again, thanks for the reply.

So, the owner of the park doesn't want a tall structure. He suggested going with a peak over the trailer, with an "awning-like" roof over the deck. The problem is, first, it's a much lower slope over the deck, and second, it makes it feel claustrophobic under the deck roof. He's is fine with a 4' - 5' height from base to peak, though.

Snow load for the area where the park is has been rated at 35 PSF, so it's not that intense at all. And from everything I've read and carpenters I've talked to on job sites, doing a 3-beam system with a ridge beam (not board) and hangers with birdsmouth cuts at the lower ends, 2x8 rafters on 24" centres would be sufficient. I've chosen to go on 16" centres anyway, just to be safe.

You keep coming back to rafters, or to a taller roof. Neither is actually an option for me. I can't really go taller than MAYBE a 5/12 pitch, and rafters are just way out of the price range for this project. What about using an engineered, LVL beam of appropriate sizing instead of a screwed and laminated triple beam of 2x10's?

 

[Nealtw]

Again, thanks for the reply.

So, the owner of the park doesn't want a tall structure. He suggested going with a peak over the trailer, with an "awning-like" roof over the deck. The problem is, first, it's a much lower slope over the deck, and second, it makes it feel claustrophobic under the deck roof. He's is fine with a 4' - 5' height from base to peak, though.

Snow load for the area where the park is has been rated at 35 PSF, so it's not that intense at all. And from everything I've read and carpenters I've talked to on job sites, doing a 3-beam system with a ridge beam (not board) and hangers with birdsmouth cuts at the lower ends, 2x8 rafters on 24" centres would be sufficient. I've chosen to go on 16" centres anyway, just to be safe.

You keep coming back to rafters, or to a taller roof. Neither is actually an option for me. I can't really go taller than MAYBE a 5/12 pitch, and rafters are just way out of the price range for this project. What about using an engineered, LVL beam of appropriate sizing instead of a screwed and laminated triple beam of 2x10's?

I just like to talk about option that people may have not considered.

So trusses are out and for good reasons.

Are you thinking of setting the post in concrete like a pole barn?

Are you thinking full height posts down the center or a wall an top of the beam to get the height.

I am not an engineer and have always worked with them so how they decide on the size of a beam as never been my thing.

I would suspect your 3 ply 2x10s at 10 ft on the outside will do but the center one will be supporting double the weight so it will want to be bigger. A real lumber store might be able to help you with that. Most have an engineer on speed dial for LVS.

We don't ever have to glue a beam together it is just so many nails ever so many inches . On a 3 ply you always want the nails visible from the outside of the beam for inspectors.

 

[Brother Antioch]

I just like to talk about option that people may have not considered.

So trusses are out and for good reasons.

Are you thinking of setting the post in concrete like a pole barn?

Are you thinking full height posts down the center or a wall an top of the beam to get the height.

I am not an engineer and have always worked with them so how they decide on the size of a beam as never been my thing.

I would suspect your 3 ply 2x10s at 10 ft on the outside will do but the center one will be supporting double the weight so it will want to be bigger. A real lumber store might be able to help you with that. Most have an engineer on speed dial for LVS.

We don't ever have to glue a beam together it is just so many nails ever so many inches . On a 3 ply you always want the nails visible from the outside of the beam for inspectors.

What I was planning was all posts to be set into 42" deep holes with builders' tubes and set in concrete with an elephant's foot at the base. I'd be using 12' posts on the outside beams and 16' posts on the inside, cut to the appropriate heights. All would be in 12" holes.

I'm not really worried about any inspectors, as this is just being done at the park, and there are no inspections to worry about. I'm good at building, so not worried about the quality of the build, so much as seeking clarification on what size beam to use.

I think I'll take your advice, though, and look into a engineered LVL beam for the centre post. Just wondering if I can use 4- 10'6" LVL beams, connected by nailing plates on top of the 5 posts, rather than go with a single 42' beam. I don't mind the 5 posts down the middle, as they will provide anchors for the structures I'm planning on building on the deck below it. Putting in an enclosed/screened in room on the first 15x12 section, and a 12x12 outdoor bar/kitchen after that.

Really appreciate all the insight though. Thanks tons. Now, it's off to work to earn the money to pay for it all...lol. Look forward to seeing your thoughts on my last question there.

Cheers,

BA.

 

[Nealtw]

What I was planning was all posts to be set into 42" deep holes with builders' tubes and set in concrete with an elephant's foot at the base. I'd be using 12' posts on the outside beams and 16' posts on the inside, cut to the appropriate heights. All would be in 12" holes.

I'm not really worried about any inspectors, as this is just being done at the park, and there are no inspections to worry about. I'm good at building, so not worried about the quality of the build, so much as seeking clarification on what size beam to use.

I think I'll take your advice, though, and look into a engineered LVL beam for the centre post. Just wondering if I can use 4- 10'6" LVL beams, connected by nailing plates on top of the 5 posts, rather than go with a single 42' beam. I don't mind the 5 posts down the middle, as they will provide anchors for the structures I'm planning on building on the deck below it. Putting in an enclosed/screened in room on the first 15x12 section, and a 12x12 outdoor bar/kitchen after that.

Really appreciate all the insight though. Thanks tons. Now, it's off to work to earn the money to pay for it all...lol. Look forward to seeing your thoughts on my last question there.

Cheers,

BA.

You want to measure the mobile for window and door locations before you decide on post placements. That might make beams sizes change a bit, at least for the back one and the center row.

As far as beam size, we don't have that much snow load here but a 16 ft garage will gt a 3 ply 2x12.

And the 20 ft beams I have put in is anywhere from 6" x14", to 8"x 20"
So 40 ft would be out of the question
We worked at repairing rot in a church beam, that beam was about fifty feet and it was a 8"x48" gluelam.

 

[Brother Antioch]

You want to measure the mobile for window and door locations before you decide on post placements. That might make beams sizes change a bit, at least for the back one and the center row.

As far as beam size, we don't have that much snow load here but a 16 ft garage will gt a 3 ply 2x12.

And the 20 ft beams I have put in is anywhere from 6" x14", to 8"x 20"
So 40 ft would be out of the question
We worked at repairing rot in a church beam, that beam was about fifty feet and it was a 8"x48" gluelam.

Okay, so I talked with the local lumber supply store, and he ran the figures through his engineering software. It's going to take 3 double lvl beams at 42'x1.5"x6" screwed/nailed and laminated together. 1 double for the ridge beam, and a double for each of the 2 outer beams. Total cost will be a little over $1400 with tax for all 6 beams. Sitting on 5- 6x6 posts per beam, it's going to handle all the snow, wind, and partying we can throw at it.

FYI, you were one hundred percent correct on the laminated beams. Even the double 2x10 beams on the outside posts would have failed, according to the software with local wind and snow loads factored in. So, once again, thanks for the great advice, and showing me the options available. If you ever have any questions about tiling or hard flooring, please, feel free to ask. It's my area of expertise (20+ years as a custom tile installer) and I'd be more than happy to repay the favour.

Cheers,

BA.

 

[Nealtw]

Okay, so I talked with the local lumber supply store, and he ran the figures through his engineering software. It's going to take 3 double lvl beams at 42'x1.5"x6" screwed/nailed and laminated together. 1 double for the ridge beam, and a double for each of the 2 outer beams. Total cost will be a little over $1400 with tax for all 6 beams. Sitting on 5- 6x6 posts per beam, it's going to handle all the snow, wind, and partying we can throw at it.

FYI, you were one hundred percent correct on the laminated beams. Even the double 2x10 beams on the outside posts would have failed, according to the software with local wind and snow loads factored in. So, once again, thanks for the great advice, and showing me the options available. If you ever have any questions about tiling or hard flooring, please, feel free to ask. It's my area of expertise (20+ years as a custom tile installer) and I'd be more than happy to repay the favour.

Cheers,

BA.

So good you have that figured out, so maybe now you can look at the plan for placing the posts and bracing them so you can use bracing for scaffolding.


I think they could supply those beams full length so you wouldn't have to worry about the joins over the posts.

You could do forty feet with 1 ft overhang on both ends.

 

[Brother Antioch]

So good you have that figured out, so maybe now you can look at the plan for placing the posts and bracing them so you can use bracing for scaffolding.


I think they could supply those beams full length so you wouldn't have to worry about the joins over the posts.

You could do forty feet with 1 ft overhang on both ends.

Great idea about using the posts for scaffolding! I'm going to be doing the 40x12 deck as soon as I have the roof up, and am going to have all the lumber delivered at the same time, so I'll have a ton of spare wood to use for framing out a scaffold. I can only do it on the one side (deck) because the trailer is already there, and I'm not going to have it moved out and back in again, re-levelled, septic hooked back up, etc. as that was an UTTER nightmare the first time...lol That will allow me to tie in on both sides of the ridge beam, and I can handle the outer connections from the ground.

It will still be a bit of a chore raising the one outer beam to the outside of the trailer up to height, but if 2 of the three become much easier thanks to that scaffolding, then I'm sure it's only going to cost me a few cases of beer and some steaks to find a few fellow park denizens to help me hoist that heavy b*tch up into place.

Cheers,

BA.

 

[Nealtw]

Great idea about using the posts for scaffolding! I'm going to be doing the 40x12 deck as soon as I have the roof up, and am going to have all the lumber delivered at the same time, so I'll have a ton of spare wood to use for framing out a scaffold. I can only do it on the one side (deck) because the trailer is already there, and I'm not going to have it moved out and back in again, re-levelled, septic hooked back up, etc. as that was an UTTER nightmare the first time...lol That will allow me to tie in on both sides of the ridge beam, and I can handle the outer connections from the ground.

It will still be a bit of a chore raising the one outer beam to the outside of the trailer up to height, but if 2 of the three become much easier thanks to that scaffolding, then I'm sure it's only going to cost me a few cases of beer and some steaks to find a few fellow park denizens to help me hoist that heavy b*tch up into place.

Cheers,

BA.

It is all do able and I would get the posts in and cut to height and then have the beams delivered with a boom truck and set them in place.

This is the 20th century.

If you are using treated wood for the deck I would hold off on that. Building it with wet treated lumber is better, a couple weeks to dry out can make it really hard to work with.

A few dozen 2x4s and rafter material can be used for scaffolding.

I think you said metal roof, then you would be strapping with 2x4s so if you order everything for the roof you will be good to go.

 

[Brother Antioch]

It is all do able and I would get the posts in and cut to height and then have the beams delivered with a boom truck and set them in place.

This is the 20th century.

If you are using treated wood for the deck I would hold off on that. Building it with wet treated lumber is better, a couple weeks to dry out can make it really hard to work with.

A few dozen 2x4s and rafter material can be used for scaffolding.

I think you said metal roof, then you would be strapping with 2x4s so if you order everything for the roof you will be good to go.

Well, for the metal roofing, I'm going to use 1x4's for the strapping, so can't use them for scaffolding. As for the decking materials, I'd rather have them dried out a bit before building the deck, as there's not going to be as much shrinkage as they dry out, and less gapping, so that doesn't bother me. I've built a ton of decks over the years, so I know what to expect. I'm going to use 2x10 ledgers on either sides of the posts attached with carriage bolts, and a floating centre beam, so it'll be strong enough to hold the outdoor kitchen/bar with (hopefully!!!) a ton of friends on the deck and their associated drinks.

I plan on building a shed once everything else is done, so I can most likely use the extra 2x4's from that to do the scaffolding. As for putting the beams up, I can use a simple blocking and rachet straps method for raising the finished 3"x6"x42' beam. It should only weigh in around 240 lbs, so if I put blocking on the posts every 2', I can lift one side, rachet it to the post on the blocking, lift the other side, and repeat until I'm either exhausted and need a beer, or it's on the posts...whatever comes first!

Cheers,

BA.

 

[Nealtw]

Well, for the metal roofing, I'm going to use 1x4's for the strapping, so can't use them for scaffolding. As for the decking materials, I'd rather have them dried out a bit before building the deck, as there's not going to be as much shrinkage as they dry out, and less gapping, so that doesn't bother me. I've built a ton of decks over the years, so I know what to expect. I'm going to use 2x10 ledgers on either sides of the posts attached with carriage bolts, and a floating centre beam, so it'll be strong enough to hold the outdoor kitchen/bar with (hopefully!!!) a ton of friends on the deck and their associated drinks.

I plan on building a shed once everything else is done, so I can most likely use the extra 2x4's from that to do the scaffolding. As for putting the beams up, I can use a simple blocking and rachet straps method for raising the finished 3"x6"x42' beam. It should only weigh in around 240 lbs, so if I put blocking on the posts every 2', I can lift one side, rachet it to the post on the blocking, lift the other side, and repeat until I'm either exhausted and need a beer, or it's on the posts...whatever comes first!

Cheers,

BA.

Wet lumber is easier to bend back to straight but that is up to you .

Lag bolt a 4x4 to the side of the post down to concrete and set a double rim on that.

3"x6" can't be right?



I have hoisted them with come-a-longs so that will work.

 

[mark sr]

I'd also suggest waiting on the PT lumber until you're ready to build the deck. Unrestrained wet PT wood can twist into all kinds of shapes as it dries out. When it does that it isn't good for much other than to be cut up into short pieces or tossed out.

 

[Nealtw]

It is all do able and I would get the posts in and cut to height and then have the beams delivered with a boom truck and set them in place.

This is the 20th century.

If you are using treated wood for the deck I would hold off on that. Building it with wet treated lumber is better, a couple weeks to dry out can make it really hard to work with.

A few dozen 2x4s and rafter material can be used for scaffolding.

There are some tricks to lining upo the posts with less of a fight we can talk about.


I think you said metal roof, then you would be strapping with 2x4s so if you order everything for the roof you will be good to go.

See if you can make sense of this picture of bracing and scaffolding.

 

[123pugsy]

You mention 42" deep holes. Ontario frost level is 4'. I would go all the way to 5'
Sure wouldn't want your hard work heaving up.

 

[Nealtw]

You mention 42" deep holes. Ontario frost level is 4'. I would go all the way to 5'
Sure wouldn't want your hard work heaving up.

He could stay with the same post just a deeper hole for the concrete, yes?

 

[123pugsy]

He could stay with the same post just a deeper hole for the concrete, yes?

Yes, however, soil should be checked for proper footing size of course.
If this were to be inspected, they would surely ask for a 20" round or 16 x16 square.


I used Bigfoots. Fantastic footing forms.