Bearer is bowing under the strain.....

[dna]

Hi,

Am wondering what to do about a problem bearer. I recently purchased a 100yr old timber house and am wanting to sort out the bearer in the attached photo (ignore the red arrow).

All the bearers under the house seem to be being 4"x2" (with the 4" in the vertical direction), except that is for the bearers running down either side of the central corridor. These are 2"x3" (with the 2" in the vertical direction). I'm not sure why these are different but they have walls above them (maybe because the load is spread by the wall whereas a bearer below open floor will see higher point loads?).

Anyway, one of the walls has been removed and the 2"x3" bearer below that section is bowing between the stumps. The section impacted is roughly 7' long (although the bearer is longer than that). The bow between stumps doesn't seem to be more than a few mm and I suspect the wall was removed 30-40yrs ago and so I don't think it is happening quickly but the floor boards are squeaking and are starting to show slight gaps. The stumps are spaced at about 3'2".

Any ideas as to what I can do to sort this out? I don't particularly want to have to put in additional stumps (there's only a few feet to work in) or lower the existing stumps to increase the cross section of the bearer. There's only 1/2" space on the top of the stump and so it'll be difficult to put another bearer in parallel.

I was thinking that screwing a metal plate (or an angled piece for even greater rigidity) to the base of the bearer might pull it straight and provide the additional strength required but I don't particularly want to have to raise the bearer to fit in the metal as it will mess up the floor levels. This would mean I could only screw the metal to the wood between the stumps. Could I do this without splitting the wood?

Interestingly, the parallel bearer of the same dimension is not showing any similar signs of bowing despite greater spacing between the stumps (3'6") but it has not had the wall above it removed.

Any bright ideas about how to do this or comments/ridicule of my only idea would be greatly appreciated.

Thanks
Duncan

[Shedhand]

A bit of clarification is needed here. Not sure what you are referring to as bearers. Bearers are the timbers which sit on the stumps. Joists sit on bearers usually at 90 degrees. Flooring is nailed to joists. Are you referring to bearers? Is it a bearer that is sagging? Or a joist?

[pawnhead]

Easy.
cable truss (http://www.pryda.com.au/catalog.php?sectionid=20&type=Builders%20Hardware&conn=BAC200) :wink:

[joe greiner]

A bit of clarification is needed here.

Sure is. Your terminology is confusing. And the sizes cited seem somewhat flimsy for floor construction; although shorter spans might validate them.

Only a few mm sag in a 100-yr-old house doesn't sound alarming, unless it's quite a few.

In general, spans can be stiffened, as well as strengthened, by addition of metal plates, which don't need to extend all the way to the supports. But they won't remove the sag, unless you jack up the "bearer" with the plate below before making final attachment, so as to camber (or pre-curve upward) the assembly. Pre-drilling for screws should alleviate splitting. As to the amount of camber needed, this calculation is best left to an experienced builder or an engineer. I'm not licensed in Oz, and frankly I wouldn't do the engineering by long distance anyway.

Joe

[pawnhead]

In general, spans can be stiffened, as well as strengthened, by addition of metal plates, which don't need to extend all the way to the supports. But they won't remove the sag, unless you jack up the "bearer" with the plate below before making final attachment, so as to camber (or pre-curve upward) the assembly.You wouldn’t have to have the flange on the angle going under the bearer. Although it would be better giving support under the bearer, it would be a little bit more hassle to install. You could rely on the bolts to hold up the bearer.
Drill three holes in the steel before you go under the house with your drill, bolts spanner and car jack. Jack up the bearer and bolt it on.
Or just drill one hole in each end of the steel. Hold it up against the bearer, with the flange underneath the bearer, and mark one of the holes. Drill and bolt it on at one end. Put a packer on the flange in the middle, and jack up the other end. Check that the bearer is straight and adjust the thickness of the packer if it’s not. When you’re happy, drill and bolt the other end.
It would be cheaper than a cable truss, and just as easy (if not easier) to install.

[Shedhand]

If it is bearers you're talking about, then the simplest and cheapest way to fix it is to jack the offending bearer up slowly - say over a week - a centimetre at a time so the floor boards don't get damaged. Then remove the ant-caps on the two stumps. Remove a coarse of bricks (or cut the equivalent if the stumps are wooden), replace the dampcourse and underpin the bowed bearer with a new bearer. Releast the floorjack slowly. Bob's you're uncle. Joe's right though, 4 x 2 seems a tad underdone for bearers. More suited to joists. My bearers are 8 x 4's and joist 4 x 2's. I had a sagging bearer in my new extension and tried the metal plate solution but the bearer still sagged so jacked the bearer up past straight, got the nail gun out and fixed a 1.8 metre length of 140 x 32 Tas Oak framing to each side. No more sag.
Hope this helps

[pawnhead]

Sorry Shedhand, but that doesn't sound simple to me at all. Bob sounds like a slave driver, not your uncle.
Whack a steel angle on with a couple of bolts FTW :2tsup:

[SilentButDeadly]

I was struggling with the photo for a bit but now I think I have it.

I'd be looking to a length of galvanised RHS 50mm square with 3.2mm wall thickness or better. It'll need to be long enough to run from the bearer in the foreground that runs at a right angle to the damaged one to a similarly arranged one that I think I can see in the distance. You'll need some flanges at either end to bolt into these bearers.

Jack up your slumping 2x3 and place the RHS on the face you can see in the photo. Bolt it in either end and at intervals along the 2x3. This will help support the 2x3 while it carries the load.

Extra support can be provided by a flying truss arrangment on the steel. In the middle of the gap between the stumps, weld in a 150mm length of 10mm steel rod on the bottom face so it is pointing straight at the ground. Take another longer length of the same material and weld one end to a point close to one stump on the bottom face of the steel, run the length across the end of the first rod and across toward the other stump to form a low large triangle (actually two triangles). These really strong triangle will help prevent any bending of the steel.

In the end, however, you probably really need the services of a structural engineer.......just to be safe and sure.

[pharmaboy2]

I know its already been said, but given its not causing huge damage above, and may ahve been like that for yonks, consider the slow jacking up of the offending bit, and some timber along side , but short of the stumps (after all, a 2/3 can take an awful lot of load if its only got to span a ft), and either nail with framing gun if you have one, or screw with pre drilled holes with batten screws, maybe 8 or 9. In my place wiuth a similar problem, I put a new 90/70 HW bearer alongside, and put 3 M10 bolts through plus a few batten crews just for good measure - although I never jacked it up, as it didnt seem like it was going to help - I just wanted to shore up what had already gone on.

If the roof is droping, or damage apearing nearby, then I'd definately get professional advice.

[dna]

A bit of clarification is needed here. Not sure what you are referring to as bearers. Bearers are the timbers which sit on the stumps. Joists sit on bearers usually at 90 degrees. Flooring is nailed to joists. Are you referring to bearers? Is it a bearer that is sagging? Or a joist?

Thanks for all the replies...

Sorry I wasn't clear. It is a bearer that is sagging. The bearer in question is 3 x 2 (with the 2" in the vertical dimension). In the picture it is the bearer running into the distance across four stumps (the stump with the red arrow pointing to it is supporting an entirely different bearer). The spacing between the stumps is roughly 3 feet.

What are people referring to when they mention flanges? Any photos?

Is there likely to be any expansion/contraction issues with the temperature changes?

I'm torn between the option of a metal plate and the wooden support.

[dna]

You wouldn’t have to have the flange on the angle going under the bearer. Although it would be better giving support under the bearer, it would be a little bit more hassle to install. You could rely on the bolts to hold up the bearer.


Is the idea behind this to run the metal support across a number of stumps or just for short (3 foot) sections between the stumps?

[silentC]

That looks like an incredibly bodgey job to me. I've never seen anyone use a 3x2 on the flat as a bearer. It'd be putting in some new stumps and getting a decent sized bearer in there. That thing isn't strong enough as a joist let alone a bearer.

Bit hard to tell from the pic, but it looks like you have every second joist sitting on the bearer in the middle of a span between piers, is that right?

[dna]

That looks like an incredibly bodgey job to me. I've never seen anyone use a 3x2 on the flat as a bearer. It'd be putting in some new stumps and getting a decent sized bearer in there. That thing isn't strong enough as a joist let alone a bearer.

Bit hard to tell from the pic, but it looks like you have every second joist sitting on the bearer in the middle of a span between piers, is that right?

The only thing that makes me question whether its dodgy is that the parallel bearer is identical (although no walls taken out above it) and it's showing no problems after 100yrs. I'm pretty convinced it is the removal of the wall above the bearer that has introduced the problem.

Will have to check the joist spacing but yes there are joists sitting on the bearer in about the middle of the span.

[silentC]

I can tell you right now that the bearer in question would never pass current building standards. But then the majority of the house frame probably wouldn't.

The reason I can tell you it is dodgy is because it is bent like a banana between those two piers. A decent bearer sitting on edge would never do that. If others in the floor haven't gone the same way, it's good luck not planning :wink:

[silentC]

Another point: in modern building design, and I would have thought the same held true back then, the floor holds up the walls, not the other way around...

[TEEJAY]

Another point: in modern building design, and I would have thought the same held true back then, the floor holds up the walls, not the other way around...


Some people get lucky and the panelling on the wall stiffens it like a bracing sheet and the wall supports itself. Being an old house it most likely has masonite or similar lining.

I know what you are saying and it doesn't comply with theory and regulations but it works this way all the same.

[journeyman Mick]

Silent,
in some older construction styles the floor is held up by the walls. The house I grew up in in Sydney was double brick on sandstone strip footings. The floors were supported on the sandstone blocks that formed the base of the walls.

Mick

[silentC]

Well, yeah but that's a different style of floor. This one is a platform floor with the walls sitting on the floor. I think the style you're talking about there is called a balloon frame? The walls go up first and then the floors are suspended between and there is a solid foundation under each wall.

[joe greiner]

Yeah, that one threw me from the outset. How could removing the wall make the floor sag? Doesn't really matter, I guess. If sag correction is desired, lots of suggestions here.

Joe