Jacking up wall/floor

[Fash]

I'm sure the answer's here somewhere but I can't find it. Lots of information about Americans jacking up their houses but since these are mostly stapled together it's not really relevant to my 1750 townhouse! The problem is that at some point in the 50's the previous owners of my house took out a wall in the basement and on the ground floor without putting in proper support. The beam they used in the cellar went in sideways (H beam instead of I beam which is about a quarter of the stiffness.) As a result there is a significant deflection on the beam in the cellar which translates into a bow in the floor at ground and first floor level. I'm having it dealt with by putting in new steels at first floor and ground floor level. The question is what is the best way of raising the floors back to approximately level before putting the new beams in? I don't really want to just preserve the existing bow although some unevenness will remain after jacking. Is it is simple as tightening the acrows until they lift the structure or would I (or at least my builder) be better off using a second set of Acrows with hydraulic jacks to do the lift with the original acrows then raised to take the load. This way I could raise it a little on the hydraulics and then move up the screw jacks to maintain the lift. Anyone done this before? All advice (although especially good advice) welcomed.

Fash

[Peter Crosland]

Sounds like the advice of a qualified structural engineer would be advisable.

Regards from Peter Crosland

[Lobster]

You have absolutely *got* to take the advice of a structural engineer over this. Have you really not already done so?

IANAE but surely there would be a real risk of totally buggering up the house by cranking the structures up as far as their original positions. Really not worth risking losing your house (life?) over a couple of hundred quid's worth of fees.

David

[Jonathan Pearson]

Fash wrote: SNIP

Steel doesn't creep, so assuming that the live load hasn't changed much (and that the beams haven't deteriorated over time and been subject to a fire etc), then the deflection occurred when the modification was undertaken, hence the deflection won't get worse due to the deadload - however as the beams were installed sideways (why???) as you rightly point out the strength has been reduced somewhat, and may deflect due to the live load (do you get cracking in walls etc), but nevertheless given the time its been there its unlikely to be unsafe!

You could do nothing and live with the deflection (if the live loads are okay), however as other have pointed out you need a structural engineer and competent builder to undertake these works as there are lots of considerations, such as beam design, pad stones, method of works, accrow design and location etc.. + all the consequences of jacking and moving the up the above walls - if you plan to change the steels, warn the wife before the quote comes in that a family holiday might be out of the question for a good few years!

Jon

[fred]

From the sound of it, it's only the floors, doesn't sound like the mother of all disasters in the making to me.

[bigcat]

If the only thinkg you need to move is a suspended wood floor, it can be jacked up on car jacks, removing loads off the floor first. It can then all be propped while the steelwork is removed.

If OTOH you wish to move a structure that supports a wall, as others have said I wouldnt consider it at all, not without expert advice at the minimum.

NT

[Fash]

I'm not completely stupid, so YES I do have a structural engineer, =A31600 so far and still counting. Quote for replacing/renewing steels is ~=A313k including some other stuff I haven't described. I generally find it helps to be informed before speaking to my structural engineer since I last did any beam calculations at Uni ~12 years ago. That's why I asked for anyone with experience of doing it/seeing it done to comment. I am also aware that any deflection took place when the inadequate steel was put in before. The point still remains that the house dropped when the steel was put in due to its inadequacy (the deflection on the steel doesn't need to be measured it can be seen with the naked eye) and I'd like some of it back. Anyway back to the first point, of course I will speak to the Structural engineer I just want to go in armed with suggestions, so far it's definitely helped me to get what I want in terms of design.

Further practical advice welcomed.

Fash

[e-mail] wrote:

[Owain]

T i m 's gotta mate selling a 4 post car lift ....

Owain

[Mike B]

One key point when jacking the middle of any beam is how far does it extend into the walls. If the walls have been built onto (or settled onto) the beam entering them at a certain angle then you will need to support the beam at the ends and remake the wall supports as well.

[tony sayer]

In article , Mike B writes

FWIW I remember many years ago knocking out the middle wall to make one big room downstairs, and after winding the acrows up and new beam in and well hammered shims into place on the new engineering brick support some of the doors upstairs opened a whole lot easier:))

[Andy Luckman (AJL Electronics)]

Strange, by posting upside down and not trimming a single syllable, you certainly appear so.

[The Natural Philosopher]

No, thats merely usenet inexperience and a welcome lack of pedantry and the sort of patronising attitude that comes from those who learn to use Usenet 10 years after everyone else, but 2 years before the current newbies.