RSJ Sizes for 7m garage ??????

[Thewhitehouse]

I am building a brick garage 6.7 m wide by 9m long and would like to have an internal garage space free of pillars or posts. The garage will be of brick and block construction and insulated. It will have a timber roof joists with clay roof tiles. The upper floor will be in the eaves and used for storage or the granny one day !

Whilst i appreciate it is a long span, any idea What size rsj would I need , each end of the rsj will be sitting on the internal blockwork spanning the 6.5m width of the garage .

I guess I would need two or three of these running the width of the garage ..

Any help would be much appreciated,

Mark

 

[freddiemercurystwin]

You doing this to Building Regs?

 

[Thewhitehouse]

Bulding Notice , so yes will need to be approved by building regs,
Mark

 

[angelboy]

I have a 7600mm x 7600mm, cavity walled brick and block (300mm) with a habitable space in the roof and I've had a structural engineer design the steels, floor joists, padstones, garage door pier stability calcs and foundation details.

It's a lot more involved than just a steel size for todays regs.

My steel is 203 x 203 x 52 spanning 6400mm due to the piers being 375mm front and back.

The foundations alone for the front door pier was 1800mm x 1800mm and 2000mm deep. Something that everyone, including the BCO thought was excessive but it's designed and calculated so it was built!

 

[tony1851]

The foundations alone for the front door pier was 1800mm x 1800mm and 2000mm deep.

Unless the garage is built on mud, that seems absolutely ridiculous.

 

[RonnyRaygun]

The foundations alone for the front door pier was 1800mm x 1800mm and 2000mm deep.

Unless the garage is built on mud, that seems absolutely ridiculous.

+1

 

[RonnyRaygun]

I am building a brick garage 6.7 m wide by 9m long and would like to have an internal garage space free of pillars or posts. The garage will be of brick and block construction and insulated. It will have a timber roof joists with clay roof tiles. The upper floor will be in the eaves and used for storage or the granny one day !

Whilst i appreciate it is a long span, any idea What size rsj would I need , each end of the rsj will be sitting on the internal blockwork spanning the 6.5m width of the garage .

I guess I would need two or three of these running the width of the garage ..

Any help would be much appreciated,

Mark

If you aren't too concerned about limiting your floor depth, then a 254 UC at mid span with similar depth easijoists would do it.
But you might need additional steels to support the dormer walls and/or roof depending on the design of the upper level.

There will be quite a bit of additional design that you should get an SE for.

 

[themiddleagedun]

The foundations alone for the front door pier was 1800mm x 1800mm and 2000mm deep.

Unless the garage is built on mud, that seems absolutely ridiculous.

You can't beat a bit of over-engineering Tony

 

[angelboy]

I totally agree.

Everyone that has to accept any liability whatsoever is being overly cautious.

Building Control, NHBC & warranty companies, SE's, builders architect etc etc.

No-one wants the finger pointing if something fails and worst of all, no-one want to be sued!!!

 

[angelboy]

The foundations alone for the front door pier was 1800mm x 1800mm and 2000mm deep.

Unless the garage is built on mud, that seems absolutely ridiculous.

It's still way over the top but let me explain a little more.

The wall between doors is 490mm with the return being 375mm (the return was designed for structural stability, taking the steel, which takes the floor and then the above brickwork, the roof trusses and the roof).

This inverted 'T' shaped wall then has a foundation design that is also following the 'T' shape but it was easier to dig a square 2m (I think it was about 1500mm fill the rest being brought up by blocks - a BCO request for ground conditions not an SE design) deep than to follow the 'T' shape.

I think the picture should explain it better.

View media item 68706
It's still over-engineered though but the cost in extra concrete was cheaper than a second opinion from another SE so whatareyougonnado?

 

[tony1851]

a BCO request for ground conditions not an SE design

In effect,then, the BCO has over-ridden your SE. Should their be any failure (eg by settlement) in the future, would the Council take any responsibility? - I doubt it.
Would your SE? probably not because his design had been changed.

In practice with a footing that size, you almost certainly shouldn't have a problem, but it does raise the issue of (structurally unqualified?) inspectors effectively altering designs prepared by (presumably qualified?) engineers.

 

[angelboy]

The SE is concerned with the point loading of the material weights that the foundation is taking. SE designed the pad to a depth of 600mm.

BCO want the depth to satisfy ground conditions and tree roots.

I don't see anything wrong with that. Neither does the BCO or the SE.

 

[tony1851]

SE designed the pad to a depth of 600mm.

BCO want the depth to satisfy their preferred depths due o ground conditions and tree roots.

I don't see anything wrong with that.

That's fair enough and in most cases there wouldn't be a problem. But if a certain pad size (in terms of area) has been specified by the SE, and the BCO wants it deeper, it will result in a greater mass of concrete over the same pad area. If the ground bearing strength was critical, then this could cause a problem.
But yes, in most cases the SE would hopefully have designed a pad in excess of the assumed bearing strength so it shouldn't in practice be an issue.

 

[angelboy]

I still think it's way over the top, as I do with most of what's underground these days.

I've said it before but every link in the chain doesn't want any liability so they tell you to stick a bit more concrete in or dig it out a little deeper.

I doubt my property is on more than 600mm in total, yet it's stood for 60 years with no issues. I'm now building in the garden yet the BCO wanted 2000m trenches within 3000m of a hedge and if I'd have gone through the NHBC they'd have wanted 2500mm?!?!?!?

Craaaaaazzzzy!

 

[angelboy]

But if a certain pad size (in terms of area) has been specified by the SE...

It was something to do with the point load on the pad was too great so the concrete would crack upwards towards the edge so the edges had to move out creating a greater area.

I don't fully get what the SE was on about but he has some fancy calculations that back up what he's saying.

On the main house there's a point where the load is 5 times greater than a standard width footing can cope with so he's designed another trench even bigger than the one in the garage.

Like I said, a second opinion will cost more than the hole full of concrete!