more on my floor - with pictures

[Sal]

finally found my camera. so to recap - although I am happy to accept springy floors - this one is ridiculous - and i expect to arrive downstairs the quick way any time soon. upon lifting the 1/2" chipboard, we discover the original joists are very beetle attacked and have been cut. some 'person' strengthened the floor by adding in 4x3 joists - for a room span of 4.1m, woefully inadequate. the inserting of these joists was done by cutting thru the noggins to which the lath and plaster is attached, and cutting the original joists away in places, presumably to insert a wall plate?

in this second image i have put a bit of string where the wall edge is

and you can probably see where the 'cuts have been made, its pretty much dust.

to put in joists for span according to building control - we would either have to lower floors downstairs (not going to happen cos its already too low), or raise floor, in order to accomodate joist height.

another option is to put in more of the 4x3s - at about 3
00 centres - which would make for a springy but not life threatening floor, and would keep the floor and ceiling heights. but of coure there only way to accomodate these would be to remove whats left of the original, to make space for the new. have to say i am amazed ceiling is staying up since it is attached to cut wood which is not resting on anything, and think if i removed the wood chipp paper that would be enough to bring it down - already you can make the ceiling go up and down by just gently prodding it.....

so now I have better explained the situation, what would you do?

 

[andrew gayton]

more 4x3's would be the easiest way to go; theses could be made stiffer and therefore less springy by adding mild steel to sides or by adding herringbone brace at 90o to new joisting.. btw, what do you mean by adding a wallplate?

 

[Sal]

is it wall plate or sole plate? hmm what I mean is a bit of wood resting on the top of the stone wall to which the joists were attached.

 

[Lime]

Hmmm.
There is a lot I can't see.
Can we have a lot more pictures?


I wouldn't use mild steel andrew gayton , not with wood.
It expands very differently to wood and 4+ metres is a long piece of steel.
Besides I don't think it would stop much of a spring in the floor as that length of steel, even in a box shape, deforms quite a lot under load.
If you use very heavy steel it might be more rigid but the extra weight will cause problems where it rests on the load bearing wall.

It looks a difficult job to bring the two goals together: Make the floor safe and keep the old fabric.

 

[NT]

When repairing an existing floor there is no reason to bring it upto new build standards, so you can forget about 2x10s or whatever.

The obvious solution is to put 4x4s in there, cutting away any of the old structure where necesary. Spacing the 4x4s closer than usual will help with rigidity. 16" spaced 4x3s is only barely enough, and not good strength wise, so quite a bit closer spacing would be good.

You can also strengthen floors with a few rows of accurately fitting noggins. Continuing these to each wall and attaching to the wall would really help with rigiity.

If you need any more rigidity, by screwing your wood flooring down every 6" would create a stressed box construction.

A strengthened 4x4 floor would be pretty solid.

Re the ceiling, it can be attached to the new woodwork using screws and large repair washers sunk slightly into the plaster, then filled over. I'd attach it to what good wood is there now first, as it sounds precarious.


NT

 

[andrew gayton]

steel strapping on sides of joisting works well from my experience.

 

[Nemesis]

It's certainly widely used.

 

[middi]

You have had vey helpful responses Sal, the truth is that what you really need is someone with a lot of understanding about these floors to look and evaluate what is the best approach to safeguard as much of the original as possible.

This may involve a combination of steel, wood and tension bars.

As to how the dimension and quantity of the above that will be utilised, it very much depends on the individual application.

These kind of repairs are usually done beyond the calculation of contemporary building regulation specifications, and rely totally on experience and intuition.

 

[Sal]

well, thanks for the replies everyone.

Sal