Raising rafter ties

[cma3169]

I have a 20x20 block garage and I'm wanting to raise the ceiling joists up about 3 feet to give me a higher ceiling. I would like to put ceiling joist/rafter tie where the tape measure is pointing or is there any other way to give me the highest ceiling possible without tearing down and building a whole new roof? Or is there a way to make a vaulted ceiling or a cathedral ceiling to give me more headroom

 

[acer66]

Depends how high your roof is.

 

[billconner]

The code usually allows you to raise these 1/3 of rafter. Can't tell from photo if you are within that or not. BUT the rafter span for a given size rafter is reduced - close to a third when tie is raised it's maximum. So could have to add/sister rafters.

An engineer or architect might be able to design a beam or horizontal truss and attachment at the plate. Like a 2x12 or two horizontally to stiffen top of wall and resist outward force of rafters.

 

[cma3169]

The code usually allows you to raise these 1/3 of rafter. Can't tell from photo if you are within that or not. BUT the rafter span for a given size rafter is reduced - close to a third when tie is raised it's maximum. So could have to add/sister rafters.

An engineer or architect might be able to design a beam or horizontal truss and attachment at the plate. Like a 2x12 or two horizontally to stiffen top of wall and resist outward force of rafters.

The code usually allows you to raise these 1/3 of rafter. Can't tell from photo if you are within that or not. BUT the rafter span for a given size rafter is reduced - close to a third when tie is raised it's maximum. So could have to add/sister rafters.

An engineer or architect might be able to design a beam or horizontal truss and attachment at the plate. Like a 2x12 or two horizontally to stiffen top of wall and resist outward force of rafters.

 

[cma3169]

Does this picture help? I'm having a hard time trying to post pictures

 

[cma3169]

Depends how high your roof is.

Its 11 foot from the concrete floor to the top of the ridge board

 

[472scout]

Jack up roof and lay blocks.

 

[cma3169]

Jack up roof and lay blocks.

I ain't thought of that. Are you saying use bottle jacks and at what spot would I jack the roof up on the rafter ties?

 

[Firebrick43]

I ain't thought of that. Are you saying use bottle jacks and at what spot would I jack the roof up on the rafter ties?

sure, I would run a temp beam under them so one jack is spread out over 4 or 6 ties. Of course you need to do it some what quickly at a time with low wind

 

[acer66]

Its 11 foot from the concrete floor to the top of the ridge board

The important measurement is from the bottom of your rafter ties to the top of the ridge beam.
You divide that by three and that number is the maximum height. you can raise your rater ties from the top of the cinder block wall.

I did that in my garage and went from 8’ to 10’ ceiling height.

My garage is 22’ between the walls and by raising the rafter ties as much as possible I was able to I replaced them with 2x12 and put insulation in there and created an attic while doing so.

 

[cma3169]

I just measured and it's only 4 foot from the bottom of the rafter ties to the top of the ridge board, so that's only a little over a foot higher. Just wish I could make it a little higher than that. Thanks

The important measurement is from the bottom of your rafter ties to the top of the ridge beam.
You divide that by three and that number is the maximum height. you can raise your rater ties from the top of the cinder block wall.

I did that in my garage and went from 8’ to 10’ ceiling height.

My garage is 22’ between the walls and by raising the rafter ties as much as possible I was able to I replaced them with 2x12 and put insulation in there and created an attic while doing so.

 

[ndm]

God do I wish I had rafters instead of bobtail trusses!! My case would be so much easier.

 

[cma3169]

Could this be made Into a vaulted ceiling

 

[billconner]

Can you support the ends of a ridge beam (installed under ridge board)? I don't know what's under the ends of ridge - wall or garage door. If so, you can just remove ceiling joists/rafter ties.

 

[cma3169]

Can you support the ends of a ridge beam (installed under ridge board)? I don't know what's under the ends of ridge - wall or garage door. If so, you can just remove ceiling joists/rafter ties.

On the back end it's a wall and then on the front wall a ridge beam maybe could maybe be supported by the block column that is separating the 2 single garage door openings

 

[Denwood]

For sure you could do a ridge beam there. It’s just a question of size and number of plys for a build in place beam. Depending on span, steel may make more sense. Either way you’d need to support both ends either with added posts, or appropriate structure in the walls. You may or may not need to add footers at the posts..depending on your foundation.

It’s quite doable Check the first page of my garage thread…I did a ridge / vault In a similar garage.

Woody's Works Garage

Woody's Works Garage - rebirth! Edit: This thread was originally just a ceiling raise project. Thanks to this forum (damn you all!) the project has, well, morphed into a six month and counting project :) I was inspired by a build found here on the journal, so am returning the favor for anyone...

www.garagejournal.com

 

[cma3169]

For sure you could do a ridge beam there. It’s just a question of size and number of plys for a build in place beam. Depending on span, steel may make more sense. Either way you’d need to support both ends either with added posts, or appropriate structure in the walls. You may or may not need to add footers at the posts..depending on your foundation.

It’s quite doable Check the first page of my garage thread…I did a ridge / vault In a similar garage.

Woody's Works Garage

Woody's Works Garage - rebirth! Edit: This thread was originally just a ceiling raise project. Thanks to this forum (damn you all!) the project has, well, morphed into a six month and counting project :) I was inspired by a build found here on the journal, so am returning the favor for anyone...

www.garagejournal.com

Hey I've seen your thread before . I think what you did should work in my garage

 

[Denwood]

It will. Find a local truss manufacturer that sells LVL beams. They should have an engineer on staff who can spec your setup.

 

[Dan in Pasadena]

It will. Find a local truss manufacturer that sells LVL beams. They should have an engineer on staff who can spec your setup.

Do NOT try to figure this out yourself nor ask a friend who is "good at math". Get a licensed engineer whose job it is to calculate these trusses every day. I'm sure Woody will agree.

 

[billconner]

It would be good to have an architect or engineer look at this. I'd suspect wall at rear is strong enough if no openings in it. Worse case you might have to core fill some blocks. If you have to add single doors, a block or steel or wood column would work but may need a new footing.

What is length of ridge? I find LVLs top out around 20' and that would be 14" or deeper.

 

[danfromsyr]

I don't see what would keep your walls from bowing or your roof from flattening if you goto vault it.
something has to hold the walls together.
I don't think you can raise the rafter ties much, say only about 6-12inches with how short your roof peak is already.

I'm not saying it'll fail immediately since you're not in snow country. but it won't be right
and you'd be leaving a structural issue for the next person.

 

[billconner]

I don't see what would keep your walls from bowing or your roof from flattening if you goto vault it.
something has to hold the walls together.
I don't think you can raise the rafter ties much, say only about 6-12inches with how short your roof peak is already.

I'm not saying it'll fail immediately since you're not in snow country. but it won't be right
and you'd be leaving a structural issue for the next person.

True without a ridge beam,but with a ridge beam it supports both ends rafters and there is no outward force like there is when ridge is unsupported and like a hinge. Rafters are just like level joists with just vertical loads at their bearing points.

 

[Firebrick43]

LOL, there are many things I will say you need and engineer such as truss modifications.

Rafters are not one of them. Rafter and beam tables for solid wood and LVL are easily available online, conservative, and easy to understand.

The AWC has online calculators available as well. There is little to no math needed either, just know where you live so you can find the local snow load and take that number down into the span tables.

I know several contractors that build exclusively with rafters just so they don't have to hire engineers.

 

[cma3169]

LOL, there are many things I will say you need and engineer such as truss modifications.

Rafters are not one of them. Rafter and beam tables for solid wood and LVL are easily available online, conservative, and easy to understand.

The AWC has online calculators available as well. There is little to no math needed either, just know where you live so you can find the local snow load and take that number down into the span tables.

I know several contractors that build exclusively with rafters just so they don't have to hire engineers.

Well said firebrick43 haha

 

[billconner]

rereading, how wide is block column between overhead doors? if is a full block or more, I think reinforced and grouted it would support ridge beam. Certainly would carry load. Just need to be sure it won't buckle parallel with ridge and that it has a footing.

 

[Denwood]

I know several contractors that build exclusively with rafters just so they don't have to hire engineers.

A local truss manufacturer took my roof size and pitch etc. …and their engineer plugged it into their software to spec the beams. It was free as I purchased the LVLs from them. What they don’t do is spec the ridge beam stabilizing collar ties, hurricane straps etc to integrate the ridge beam to existing ridge board etc.

It is not rocket science by any stretch but someone with industry software can make it very easy for you

The end support does not have to be inside the walls. You can add footers and do the support posts inside the structure too. This way the wall tie in can stabilize your post, but not take any ridge beam load.

My partial ridge called for two 1 3/4” x 12” LVLs for a 16ft ridge and the two horizontal beams (same spec) that take the ridge load to side walls. 4x4 posts. Our snow loads are very high here.

 

[billconner]

If the block walls are plumb and not cracked, pretty good chance they have a functioning footer. Block is minimum 1900 psi compressive, so just a single core grouted is over 120,000 pounds. Just seems simple compared to adding 2 footers and 2 4x4s.

 

[Denwood]

For sure..if the option is there, follow the KISS rule