Is my Timber Floor Structurally Sound?

radooo

House was built 3 years ago; however the floor appears to bounce to some extent. I have removed the floor and the osb board. Photo can be seen here

https://www.dropbox.com/s/ed5zavef39ki3uu/IMG_5323.JPG?dl=0

as you can see on the picture, joists are 9x2 (4.5m long) with a 35cm spacing between joists. What concerns me are the ledger board that are the same size and it also appears they might not be attached to the concrete wall properly as I can't see any screws or sleeve anchors sticking out of the ledger.

Can you please share your thoughts?

It can be also seen on the photo that electric cables are not housed in an insulated tube to prevent from timber joists catching fire in the event of electrical wiring fault. Aren't builders required by law to place wires in an insulated tube to minimise fire danger?

Would really appreciate your thoughts. Thank you.

Gumbo

Get an engineer to assertion their suitability ASAP.


Timber requires 12kw to combust so maybe someone with electrical experience can shed some light on what kind of loading travels through the wires, although I'd imagine the trip switch will engage well before the point of combustion.

The wires do not need to be housed in any tubing that I'm aware of in a typical residential single dwelling.

antiskeptic

radooo wrote: »

House was built 3 years ago; however the floor appears to bounce to some extent. I have removed the floor and the osb board. Photo can be seen here

https://www.dropbox.com/s/ed5zavef39ki3uu/IMG_5323.JPG?dl=0

as you can see on the picture, joists are 9x2 (4.5m long) with a 35cm spacing between joists. What concerns me are the ledger board that are the same size and it also appears they might not be attached to the concrete wall properly as I can't see any screws or sleeve anchors sticking out of the ledger.

Can you please share your thoughts?

It can be also seen on the photo that electric cables are not housed in an insulated tube to prevent from timber joists catching fire in the event of electrical wiring fault. Aren't builders required by law to place wires in an insulated tube to minimise fire danger?

Would really appreciate your thoughts. Thank you.

Looking at my homebond manual.

Using the lowest class of wood (let's assume yours is). A 225 x 44 joist can span 4.6m at 350mm spacing. The joists should be bridged together at half span with 'noggins' (Google it) that are at least 3/4 the depth of the joist.

Dunno about ledger board attachment but it strikes me as unlikely they aren't attached to the wall - otherwise the floor would fall down. Perhaps the fixings hidden by the joists.

The bounce will occur mid-span so the fact the ledger board is same size as the joists doesn't strike me as problematic (unless the bounce sees the ledge board move relative to the wall.). It the ledger board where larger, it would protrude down into the room below so same size strikes me a correct.

The wiring looks standard issue. I've never seen wiring run in tubing in a house. There is no reason for the wiring to go on fire unless it's not protected properly by a trip switch (which should be rated to prevent overload of the wiring to which it's connected).

You sometimes get wiring run in tubing in industry where it goes through metal as the fretting of the wire against the cut hole in the metal can cause problems - but even in those cases, the tubing is local to the hole only, the wiring isn't run in tubing throughout.

Calahonda52

As above re wiring regs etc.

As for structurally sound, yes indeed

Re the bounce, there is always some give in a suspended timber floor.

It seems to me that the ledger board is slightly deeper than the joists which means that the OSB sits up on it and is up from the joists close to the wall.

Also I see no evidence of any fixings through the OSB so perhaps the bounce is in the OSB.

You should screw the floor down, say using 5mm by 60mm or 5mm by 75mm screws at 600mm centres, with the OSB pre-drilled and countersunk so as the screw pulling action is all in the joist.
Mark the positions of the joists and ledger, carefully, on the OSB

ps Also be aware of where the wires are passing through the joists

antiskeptic

Calahonda52 wrote: »

It seems to me that the ledger board is slightly deeper than the joists which means that the OSB sits up on it and is up from the joists close to the wall.

Good spot! That would certainly cause extra bounce and more certainly if the boards weren't screwed down. Either cut the board short of the ledger board so that the board lies flat on the joist. If that isn't acceptable (it might result in a visible step near the skirting board) then route the edge of the board so that the board is stepped and lies flat on the joists and contacts the top of the ledger board.

the_pen_turner

Calahonda52 wrote: »

As above re wiring regs etc.

As for structurally sound, yes indeed

Re the bounce, there is always some give in a suspended timber floor.

It seems to me that the ledger board is slightly deeper than the joists which means that the OSB sits up on it and is up from the joists close to the wall.

Also I see no evidence of any fixings through the OSB so perhaps the bounce is in the OSB.

You should screw the floor down, say using 5mm by 60mm or 5mm by 75mm screws at 600mm centres, with the OSB pre-drilled and countersunk so as the screw pulling action is all in the joist.
Mark the positions of the joists and ledger, carefully, on the OSB

good call. that lip is creating a bounce
how many bridging pieces are there across the span
definitely screw down the osb . I would do 400 cetres

radooo

many thanks for all your tips :-) Are you suggesting to cut a 4.5cm stripe from osb board to make sure it sits straight on joists and not the ledger board?

Calahonda52

45 mmiill be beyond skirting board so more problems.
The problem is that they are not all lower than the ledger so I would just screw it down, you could try rebate the edge of the OSB sheet but you may not have the gear for that and then if its too much, when u screw it down on ledger the rebate may break....

sydthebeat

Is that trimmer rather than a ledger?
What is the wall behind it? A chimney perhaps?

Very strange that the joists wouldn't be built into the concrete wall, or on built in shoes...

mickdw

Your span looks fine for the timber sizes.
Seems to be a lack of bridging but that may just be the camera angle.
Perhaps it's poor quality timber and the tops are not flat meaning the floor it sitting on some joists but not on others resulting in bounce.
I'd pull a line across various points when you have the floor up.

antiskeptic

sydthebeat wrote: »

Is that trimmer rather than a ledger?

No idea what it's called - just going with the OP's description for simplification
.

Very strange that the joists wouldn't be built into the concrete wall, or on built in shoes...

If built in they'd certainly give rigidity but I wouldn't see a functional issue with them as they are

antiskeptic

radooo wrote: »

many thanks for all your tips :-) Are you suggesting to cut a 4.5cm stripe from osb board to make sure it sits straight on joists and not the ledger board?

As calahonda says: simply cutting 45mm off means the board stops short of the skirting and you might have a visible step from edge of board down to ledger (plasterboard thickness + skirting might just cover this though. A rebate in the OSB is the other solution (cutting a step into the board which covers the ledger).

sydthebeat

antiskeptic wrote: »

No idea what it's called - just going with the OP's description

The reason I ask is because if it's a ledger it should be fixed to the wall, but if it's a trimmer, such as around a chimney, it won't be fixed to the wall and could be the cause of some of the bouncing.

antiskeptic

sydthebeat wrote: »

The reason I ask is because if it's a ledger it should be fixed to the wall, but if it's a trimmer, such as around a chimney, it won't be fixed to the wall and could be the cause of some of the bouncing.

Aha! Something learned every day. Ledgers and trimmers...

Hecklar

What's the thickness of your ply, and how is it fixed down? Looks like very few screws used. See if you can get someone else to bounce the floor in the middle while you look under to see where the movement is. Save you a lot of guess work.

bertie 56

That seems a poor builder job altogether...

What thickness is your OSB, by the way ?

First of all, IMO, the joists hangers should have higher flanges. They don't even cover half of the height of the joists : your joists are not maintained laterally and are crooked .
As said before, check the bridging ! That's a very important structural part .
Before closing everything again , a rebate in the OSB will make it settle better.
And plenty of screws ( pre-drill the OSB ). You can glue too if you are sure of not opening again.

About the electrician job, you are lucky, you were not far of having one joist cut with the hole saw !:rolleyes: ( How does this lamp looks like underneath ??? )

About tubing the wires , ah, well , question of taste ...

SC024

The Hangers are fine, There standard joist hangers & you don't mention any abnormal loadings etc, Re: pre-drilling the OSB there's no need Just get 5 x 60 half threaded woodscrews will do the very same job with plenty of pull but save you hardship. I wouldn't bother glueing cause you never know when you will need to take them up for pipes / cablees etc. You could rebate the back of the sheet if you really want to take the bounce out of it.

bertie 56

SC024 wrote: »

The Hangers are fine, There standard joist hangers & you don't mention any abnormal loadings etc, Re: pre-drilling the OSB there's no need Just get 5 x 60 half threaded woodscrews will do the very same job with plenty of pull but save you hardship. I wouldn't bother glueing cause you never know when you will need to take them up for pipes / cablees etc. You could rebate the back of the sheet if you really want to take the bounce out of it.

Standard doesn't mean fit for purpose...
There is a recommended ratio height of the joist / height of the timber.
( I have to find it again, it was from a manufacturer . 2/3 ? )
Anyway, it's just common sense, when you think a bit...
The alternative with these hangers would have been to put some bridging close to the ends of the joists to prevent wrapping .

About the screws, yes, partially threaded screws can be put without holes...in the middle. I would pre-drill at the edges and corners to prevent splitting, though... And all brands don't have partially threaded screws of medium size. Spax, for ex, starts at 80 .