Portal Frame Building Pads

[Wendelspanswick]

I am setting out the foundations pads for my 10m by 5m steel portal framed shed, 3 frames with one frame at 2.4m to eaves and the other two at 3.4m to eaves as the ground slopes.
The higher 3.4m to eaves half of the building will have a solid concrete floor and the other half of the building will have a suspended floor.
I will most probably spec the frames for a local fab company to make up in 175mm by 100mm UB.
So my question is what size concrete pad and how deep?

 

[Rig Pig]

Depends what sort of load you intend to put on it & the type of soil

 

[Wendelspanswick]

Depends what sort of load you intend to put on it & the type of soil

I meant the size of the pads for the portal frame bases rather than a floor.
Frames will be clad and roofed with steel box profile, subsoil is a stoney shillet, no clay or sand.

 

[Hitch]

Think he means if there will be hoists, cranes, mezz floors aswell...

 

[Wendelspanswick]

Ah I see, nothing of any great mass hanging off the building, one end will be a storage shed with concrete floor and the end with the wooden suspended floor will be a rest area with a small kitchen, sofa, shower and toilet.
Roof pitch will be 28 deg.

 

[Wendelspanswick]

Obviously that size will require planning permission (over 3m high) so surely the architect will have specified the size of the foundation pads when submitting plans to the council.

Paul H

It's an agricultural building built under Prior Notification rules so no planners or architects involved.

 

[awemawson]

It doesn't necessarily need planning permission. If it is an agricultural building it can be done on a 28 day notice if he has over 12 acres

edit: You got there as I was typing !!!!

 

[Rig Pig]

I would be inclined to go with two trenches of reinforced concrete to give it plenty of mass to resist wind and simplify levelling, have you checked for any buried cables pipes etc?

 

[Wendelspanswick]

No worries on the buried utilities as it's on virgin ground in the middle of nowhere.
Access is difficult which is why I am trying to keep the volume of concrete down, any concrete will have to be mixed in a PTO mixer. The site is well shielded by trees and the slope of the hill so I was thinking along the lines of 600x600x600mm for each pad with the concrete floor tied into four of the six pads.

 

[CompoSimmonite]

Anything over 30m square floor area requires building regulations even if classed as permitted development for planning purposes. Assuming the building regs have been approved by council don't the plans show the required size of the pads ?

Paul H

It's an agricultural building built under Prior Notification rules so no planners or architects involved.

You will see I deleted my postings virtually straight away as realised I was wrong but you must have replied anyway

Paul H

 

[awemawson]

We have always used a 1 metre cube at the foot of each leg of portal frame buildings here. No science behind it, just the considerable experience of the chap who's put mine up in the past. We are on clay by the way.

 

[Wendelspanswick]

Anything over 30m square floor area requires building regulations even if classed as permitted development for planning purposes. Assuming the building regs have been approved by council don't the plans show the required size of the pads ?

Paul H



You will see I deleted my postings virtually straight away as realised I was wrong but you must have replied anyway

Paul H

It's not Permitted Development it's Prior Notification, two different things completely.
Also agricultural buildings are also exempt from building regs (Class 3).

 

[trogboy]

Hi, this is my first post on this forum. I've been lurking and learning for a long time, but I couldn't resist replying to this thread.

Footing depth depends on consideration of the strength and compresibility of the underlying soil. If you really are into a weathered shale (shillet) then the allowable bearing capacity on flat ground is going to be more than adequate for just about any load you could apply with a building that size so small pads would be fine.

Post up some pics of the site as the slope sounds like is could be significant at one end of the building. If it really is steep the stability of the slope could affect the choice of foundation.

Ad

 

[Wendelspanswick]

Hi, this is my first post on this forum. I've been lurking and learning for a long time, but I couldn't resist replying to this thread.

Footing depth depends on consideration of the strength and compresibility of the underlying soil. If you really are into a weathered shale (shillet) then the allowable bearing capacity on flat ground is going to be more than adequate for just about any load you could apply with a building that size so small pads would be fine.

Post up some pics of the site as the slope sounds like is could be significant at one end of the building. If it really is steep the stability of the slope could affect the choice of foundation.

Ad

I am estimating the height differential at the moment as I don't know anyone with a dumpy level to borrow. I am keeping an eye on Ebay but until I get one at the right price I have gone 'old style' by ordering a 15m water level for less than £8 including postage.
It should be here before I go up to the field at the weekend where I can take some accurate levels and I will also take some pictures of the site.
Cheers.
John

 

[brightspark]

I am estimating the height differential at the moment as I don't know anyone with a dumpy level to borrow. I am keeping an eye on Ebay but until I get one at the right price I have gone 'old style' by ordering a 15m water level for less than £8 including postage.
It should be here before I go up to the field at the weekend where I can take some accurate levels and I will also take some pictures of the site.
Cheers.
John

i have a laser level i use at work regular and have a set of water levels with nice brass fittings . i scored them for 4 quid at car bootsale . the bloke didnt know what they were .he nearly choked when i said id been after a pair for years and they were for nothing