Foundations 1850

[Anonymous]

I live in a property built around 1843. It has a basement and ground, first and second floor. I am going to have some structural changes made in the basement and the structural engineer requires foundations of atleast 400mm to bear the new load. Without chipping up the concrete floor it there any other way of working out how deep the foundations are? Is there a rule of thumb used in those days to calculate the depth and will the old foundations be sufficient? Thanks

 

[Anonymous]

Frankly in a property of this age I'd be very surprised if there were any 'foundations' in the modern sense - more usual to have 'footings' . These can vary widely as to how deep they are.

It strikes me though that the house has been supported on these for a very long time without collapse...
but I appreciate that modern building regs may come into play here. I

 

[Anonymous]

I agree with Evelyn. Foundations are likely to be negligible.

What exactly are the changes in your basement which require this?

 

[Anonymous]

Well, two rooms were split in two but a ridiculous amount of wall was left in place. So removing the remnants of this wall. The rsj above it supports all the other floors joists which run from the fron to rear of the property.
The second change is knocking through two old coal "bunkers" which at present are deep brick built arches. By removing the end of these which form part of the rear outside wall, two tunnels will be created between the kitchen and dining room!
Hope that makes sense, it is the structural engineer who has specified this depth of footing.
p.s The house has no signs of heave or subsidence.

 

[Anonymous]

oops re previous message - I meant to say two rooms were made into one larger room!

 

[Anonymous]

It sounds a bit confusing Wayne, you have done the correct thing by asking a structural engineer to guide you on this project, and at the same time you are asking about" footings" or "foundations" on this forum.
We don't mind at all about any questions to do with period properties, but it does sound as if you may not trust what the structural engineer is telling you.
The thing is ,that if you have to comply with building reg,s, it is a different ball game altogether when involves an old or historic building.
Perhaps a bit more explanation on this may give you a better response on this forum.

 

[Anonymous]

I also knocked together the front and back basement rooms in my 1840 four storey house. I decided however not to make the opening run the whole width of the room (I think it looks better this way).

My ground floor joists, like yours, run from front to back and the ground floor rooms already had an opening between them (original to the house). The beam therefore only needed to support the ends of the joists of the floor above.

The engineer specified a wooden beam, not a RSJ. Although the exterior walls of the house are brick, almost all interior walls are studwork with lath and plaster, and there has clearly been some flexing of the interior structure over time. The engineer's view was that a wooden beam would be better because it too could flex. (By contrast, when we found a half rotten wooden beam supporting some of the exterior brickwork this was replaced with steel). The rule seems to be to use rigid beams in rigid structures and flexible beams in flexible structures.

 

[Anonymous]

Thanks for your advise perhaps you are a little confused yourself middi? The engineer has recommended 400mm foundations in order to support the increased load of removing some existing structure and supporting this on a RSJ. What I was hoping to ascertain was some indication of what I might expect to find under the concrete floor in terms of existing footings/foundations. As you can appreciate time, effort and mess created from lifting areas of a concrete floor only to find underpining may be required would be fairly painful. So I am trying to get opinions about what I might find, so i can make some preliminary action plan.

 

[Anonymous]

Well - I doubt you'll find anything resembling modern foundations. If your engineer is one with historic buildings expertise he should recognise this, but it's really impossible to guess what may or may not be there frankly.