What size RSJ?

[SparkyStu]

Hi. I am a newbie to this forum so please forgive my questions if they appear basic!
I am in the process of building a garage using 4 inch solid concrete blocks with a 2inch cavity (so double skin). I am approaching the time to fit the 2 lintels for the rolloer shutter but am a little unsure what sizes to use.
The opening is 8ft 9 (2.625m). The walls to each side of the door are just 730mm outer skin, 590mm inner skin.
The height to eaves will be 3m and then a pitched roof with a ridge height of approx 4m.
Do the lintels need to be RSJs or would pressed steel be sufficient? What sizes should I be using?

In addition, I would like to have a full length RSJ at ridge height to hang a girder trolley from to use for lifting - maximum anticipated weight of less than 1000kgs. Probably 500kg realistically.
The length of span is 7.7m to outer skins, 7.4m to inner. Should this be supported on inner skins only or should it bridge the cavity to be supported by outer skins aswell?
What size should I be looking at using?

The roof covering will be sterling boards on 4x2 and then covered in profile sheeting, so no significant weight issue there.

The full length RSJ will be using the lintel over the roller shutter to support it at the front. I expect there will be 5 or 6 courses of block to the ridge, resting on the lintel in a triangular form.

I realise there are a lot of questions here but any information would be gratefully received. I do not wish to go down the Architect and Structural Engineer routes - afterall, its only a garage!!!

 

[Deluks]

after all, its only a garage!!!

A bloody expensive one after you've added those steels!

What's the span widthwise?

 

[freddiemercurystwin]

@Deluks its a brave poster who sizes steels when point loads like this are involved!

 

[Deluks]

@Deluks its a brave poster who sizes steels when point loads like this are involved!

I'll leave you to it then

 

[freddiemercurystwin]

 

[SparkyStu]

after all, its only a garage!!!

A bloody expensive one after you've added those steels!

What's the span widthwise?

You're right - I expect it will be silly money!!

The width is 4.1m to outer skins. I was thinkiing about using the width for the lifting gear but the full height isn't available then!

Any suggestions?

 

[freddiemercurystwin]

Don't be a tight ar*e and employ a structural engineer.

 

[Deluks]

after all, its only a garage!!!

A bloody expensive one after you've added those steels!

What's the span widthwise?

You're right - I expect it will be silly money!!

The width is 4.1m to outer skins. I was thinkiing about using the width for the lifting gear but the full height isn't available then!

Any suggestions?

A pair of beams going across the width with a small column fixed in the centre to give you more height, the lifting beam resting on these columns. Messy but likely to still be cheaper than a 7m+ taking half a ton in the middle! Obviously you won't have full trolley usage of the full length of the garage but you probably don't need it do you.

plus what Fred just said

 

[freddiemercurystwin]

You could PM our current resident SE Static he may be happy to advise.

 

[SparkyStu]

after all, its only a garage!!!

A bloody expensive one after you've added those steels!

What's the span widthwise?

You're right - I expect it will be silly money!!

The width is 4.1m to outer skins. I was thinkiing about using the width for the lifting gear but the full height isn't available then!

Any suggestions?

A pair of beams going across the width with a small column fixed in the centre to give you more height, the lifting beam resting on these columns. Messy but likely to still be cheaper than a 7m+ taking half a ton in the middle! Obviously you won't have full trolley usage of the full length of the garage but you probably don't need it do you.

plus what Fred just said

Thanks for the replies. Although "messy" as you say, a column in the centre of two widthways beams would be ok. I would like thelift at the front doorway to assist with moving objects into the garage and engine lifts at the doorway. In addition, I would like the lift at the back of the garage to reach the small upper floor area which is just 2m from ground floor level.

Any ideas on sizes for the doorway?

Thanks again!

 

[Static]

You could PM our current resident SE Static he may be happy to advise.

Doh..

Well, even thou ive a busy morning doing HV building design.. ill help:

Right firstly 1000kg in the center of a 7.5m long steel is pretty high for domestic stuff.. can only assume its for lift crates of drugs from the back of pickups or something.. jk

Anyways your looking at a middle-heavy sized 152UC for the length of the garage depending on the tolerance of the lifting gear on deflection.. bear in mind you may need a stiffer beam as that spec will deflect 20mm fully loaded

Then cos of the large load in the middle of the new door lintel you may need a similar sized steel on the inner leaf of the door..

The alternative is to have a standard Catnic style lintel for your roller shutter door and then build an H frame for the lifting gear...
So span some steels between the side walls at each end and a main steel at their mid span..
Joys of this way is that you reduce the overall span of the steels and thus the size required.. mostly you wont need to use the beam at the far ends of your garage anyways..
It can also be added after the garage has been built..

 

[SparkyStu]

You could PM our current resident SE Static he may be happy to advise.

Doh..

Well, even thou ive a busy morning doing HV building design.. ill help:

Right firstly 1000kg in the center of a 7.5m long steel is pretty high for domestic stuff.. can only assume its for lift crates of drugs from the back of pickups or something.. jk

Anyways your looking at a middle-heavy sized 152UC for the length of the garage depending on the tolerance of the lifting gear on deflection.. bear in mind you may need a stiffer beam as that spec will deflect 20mm fully loaded

Then cos of the large load in the middle of the new door lintel you may need a similar sized steel on the inner leaf of the door..

The alternative is to have a standard Catnic style lintel for your roller shutter door and then build an H frame for the lifting gear...
So span some steels between the side walls at each end and a main steel at their mid span..
Joys of this way is that you reduce the overall span of the steels and thus the size required.. mostly you wont need to use the beam at the far ends of your garage anyways..
It can also be added after the garage has been built..

Thanks for the reply - very helpful!

Just to clarify as I'm not by any means an expert in this field(!), a catnic would suffice for the roller shutter? I wasn't sure they were made in that length.
Assuming I wanted to use RSJs - just to complicate the job further(!) I was hoping to fit my roller shutter to the OUTER leaf and have a pair of doors on the inner. Partly so I can have some windows to let more light in whilst doors shut and partly for security. Therefore, I presume the inner lintel would need to be higher than the roller shutter as they would clash. I would only need the doors to be the height to the bottom of the roller when it is in it's rolled up state. The small gap created above the doors when it is down wouldn't be an issue.

Then I could have 2 widthways RSJs and then the main length steel sat on those 2?
That sounds like a good plan. Forgive me though, I don't understand why the main length RSJ could then be smaller? Would you then put a 3rd RSJ at midpoint of the length - ie at 3.5m to further support the length?
I like the idea and I'm coming round to it very quickly - I would just lose the extra 1m height although it may not be such an issue!

Thanks once again for the reply.

 

[Static]

What i mean with the reduced span beams is this:
Rather than run a deep beam (250-300mm deep or so) the full 7.4m length than have a heavy duty lintel for this..
Put a couple of RSJ's about 1m inside each end, thus the support beam will be 5.4m long and sitting into the middle of these beams.. you could then use something like a 150-200mm deep beam for these 3.. yes it will be lower but could be in the depth of any ceiling joists.. also could be used to store stuff in the void over..

Urm roller door on the outer leaf?! You may have something else in mind but normally the doors are set back behind the inner leaf on runners and a large box with the winch and tube to store the door when rolled..

 

[SparkyStu]

What i mean with the reduced span beams is this:
Rather than run a deep beam (250-300mm deep or so) the full 7.4m length than have a heavy duty lintel for this..
Put a couple of RSJ's about 1m inside each end, thus the support beam will be 5.4m long and sitting into the middle of these beams.. you could then use something like a 150-200mm deep beam for these 3.. yes it will be lower but could be in the depth of any ceiling joists.. also could be used to store stuff in the void over..

Urm roller door on the outer leaf?! You may have something else in mind but normally the doors are set back behind the inner leaf on runners and a large box with the winch and tube to store the door when rolled..

Thanks again for the reply. I take on board what you say about the full length of 7.4m. If this was reduced to 5.4m then the difference in size would be so much? In that case, if I change the goalposts slightly (again!!) and had the 5.4m still at ridge height but ending at 2m from the rear wall, this would take me to just above the suspended floor which is full width, 2.4m long from rear wall at a height of 2m from floor.
The end of the 5.4m length could be supported by a full width RSJ as you suggest but sat on a 1m piece of something (either steel or block or whatever) to lift it to ridge height.
The front would then presumably still sit on the lintel above the door unless a similar idea could be used from another full width RSJ.

The roller shutter has the tube and curtain designed to be mounted inside - as you say on the inner edge of the inner leaf. However, if I move that to the inner edge of the outer leaf and have the inner leaf lintel raised by 300mm (or whatever the height would be) to accomodate the tube and curtain, it should fit into place with few (that's a fatal thing to say!) problems. The cavity walls do not need to be met where the door is -in my opinion!

I apologise for my approach to simplify the problems - I appreciate it isn't quite like that. I just want to ensure that I get it right and build whatever in at the correct stage if necessary.

 

[Static]

Sorry but some of the info your giving conflicts a little.. probably cos your still not settled on final details..

You have a suspended floor at one end of your garage!? Sorry im finding it hard to visualise, some form of toilet? or is this attached to the main building? Maybe an internal garage? If so its turning from "just a garage" to a major complication..

You say theres to be a pitched roof on this, but then suggest no ceiling members, will there be roof ties higher up? Or is it in the intension to use this steel beam as the roof support? Or will the pitch have its own independant ridge beam?

Maybe some photos/plans will help?

ps.. you should check with a roller door manufacturer about your idea of external mounting they will know if its possible..