Spreader beam

[mylittlehouse]

Hay everyone, I had my end wall taken out in my Victoria terrace, the structure engineer used a portal box frame with a RSJ in the floor (spreader beam) and one supporting the bricks above and the RSJ's separated by two posts that are bolted into the walls.
This has been done.

The engineers words say that the spreader beam should sit on the houses existing foundations.
When building control came out they said they would not approve the steal work as they need to see what it's sitting on as the builder put concrete ether side.
Today I have dug out either side of the RSJ to look under it.
Now it site on concrete that was poured into the floor as the existing bricks did not go deep enough and were removed to get the RSJ in.
So it turns out that the RSJ is sitting on around 50mm of concrete where the bottom of the existing wall was.
Under this is just clay I suppose how it was built originally.
How are building control going to insist it must be on existing foundations if the never were any and the wall was originally built on clay?

Will they accept this or will I have to put in a foundation?
Ay ideas?
Can I argue there choice considering the wall was already there.
I'll post a picture if needed.

Cheers all desperate for some form of info

 

[mylittlehouse]

Hi there
After a little more digging (not literally)
The RSJ is sitting on 50mm of ballast concrete and that sits on clay that the house is built on.
The spec said it must sit on original foundations but the last course of brick was removed.

Any ideas if BC will be happy or I will need to sit a trench and put in a foundation.
The original foundation is clay, according to the spec it needs to sit on the original foundation. Does that mean clay is ok?

 

[noseall]

You will need to underpin the walls that the beam sits upon.

It is not unusual to have to beef up poor or inadequate foundations.

50mm in not even adequate for a floor slab.

 

[tony1851]

If it's an old Victorian terrace house. it's likely that the original foundation was nothing more than a slight widening of the wall just below ground level, such as a 1 1/2 brick wide footing, or possibly a 2 - brick wide footing.
If the spreader beam is fairly deep, then most of the original below-ground brickwork will have gone.

Whether or not the spreader on 50mm of concrete will be sufficient to spread the load is anyone's guess. Remember that the load distribution will now differ and, depending how the connection between the column and spreader is made, depends on how effective the spreader is in distributing the load.

You really need to speak to your SE about this; if he was aware it was an old house, he should have known that the existing footings will be relatively small.

 

[mylittlehouse]

Hi there
Thank you for some clarity.
So will BC be able to tell me what they want to see or will the SE have to tell me what I need to do for BC to be happy?
Cheers

 

[tony1851]

Hi there

So will BC be able to tell me what they want to see

No; the building inspector will allmost certainly say that he wants to see foundation calcs from your SE. These will be passed to the council's own engineer for checking.

 

[mylittlehouse]

I will call BC on Monday and let them know that the original foundation is clay and that I will speak with my SE to inform me what needs to happen and provide their info to BC and hope for the best.
Is this normal thing to have to do?

 

[mylittlehouse]

Hi all
Thought I would post a update to this.
I spoke to my SE today and he confirmed that as building control were not happy that I need put acro the frame back up so I can dig under the spreader beam.

A trench must be dug under the spreader beam to allow for a 450x450mm minimum concrete block to be made. The block must also be at a min of 900mm from the normal floor level.

BC have said they want to come and see the trench before its filled I suppose so they can confirm the total depth.

Only thing I cannot work out is how to jack up the RSJ considering I need to dig a trench below the current one, where would I out the acro stands?

Cheers all

 

[RonnyRaygun]

BC have said they want to come and see the trench before its filled I suppose so they can confirm the total depth.

Only thing I cannot work out is how to jack up the RSJ considering I need to dig a trench below the current one, where would I out the acro stands?

Cheers all

I don't understand why your SE didn't ask to see the results of trial pits before installation...

But anyway, ideally you need to support the acrows on pads of some description that keep bearing pressures below the aloowable limit for the soil. You only need to allow for dead load and a nominal imposed load of furniture though, and you don't need to worry about depth, just dig away any top soil and bed evenly.

 

[mylittlehouse]

Yeah, my architect passed details of the house to their SE, he did not visit my house.
I will get someone to dig the trench under the spreader beam but how can I put acro stands under the RSJ when the space below will be dug out?
Do I have two acro stands and something between them?

 

[noseall]

You support the beam from a distance i.e. with needles or bridging beams or prop the beam more centrally whereby the ends are being underpinned.