Joists....Have I boobed?

[Dee]

6 hours ago, joe90 said:

I maybe wrong but I cant see any supports fir that pipe., if not hot water in it may make it sag over time, if you do the “ply” thing I suggested earlier this will also support the pipe 👍 2 birds with one stone and all that 🤷‍♂️

I screwed brackets under the joists to support the waste....is that sufficient?

[joe90]

9 minutes ago, Dee said:

I screwed brackets under the joists to support the waste....is that sufficient?

Ah could not see those, yes but as said above sistering or ply will mitigate any risk of the timber You removed.

[Dee]

sistering...

My task for this week

[MAB]

When I had to add some 'sister' joists in my first floor extension to strengthen the existing joists, my Building Inspector suggested using M12 bolts with these double-sided toothplate washers 'sandwiched' in-between the existing and new timbers:-

https://www.screwfix.com/p/sabrefix-m12-timber-connector-galvanised-dx275-50mm-x-50mm-50-pack/99094

Edited December 3, 2023 by MAB

[saveasteading]

3 hours ago, MAB said:

using M12 bolts

That is a very strong solution, and best if using full sister timbers,  but its sometimes tricky to drill the horizontal holes through both pieces.

[Dee]

Is this correct?

It's 2 peices of 18mm ply. (Only glue incase it's wrong.)

500mm wide x 200mm deep

The joist is 50mm x 140mm x 1900

[joe90]

I believe that will mitigate deflection completely. 👍(now 16 screws in total) 

[Dee]

Just now, joe90 said:

now 16 screws in total

16! Blimey

 

[Dee]

Should that be 8 screws through one side and 8 the other way. Or all 16 on one side

[saveasteading]

1 hour ago, Dee said:

! Blimey

 

Try to stagger them high  middle and low and not in horizontal lines. That way you are not putting g multiple screws in a single grain.

I hope you tried jumping first, so that you can report back on the effect.

 

[Dee]

6 minutes ago, saveasteading said:

hope you tried jumping first, so that you can report back on the effect.

I have and they all seem pretty solid but then I'm not a big burley bloke!

[saveasteading]

43 minutes ago, Dee said:

they all seem pretty solid but

Well you tried anyway. 

Joists fail in acceptable deflection before the breaking point.  So you're OK.

[Dee]

 

Now ive got the sisyeting underwsy, A bit off piste. But do I have to have the bathroom skimmed yo get it through build control?

[saveasteading]

50 minutes ago, Dee said:

do I have to have the bathroom skimmed yo get it through build control

not unless there is something we don't know. Has it been asked for?

[joe90]

1 hour ago, Dee said:

 

Now ive got the sisyeting underwsy, A bit off piste. But do I have to have the bathroom skimmed yo get it through build control?

No, crack on 👍

[Dee]

Build regs guy says I might need to skim.....I used Knauf 12.5 tapered plasterboard on the walls and 12.5mm pink fire rated pb on the ceiling.

The floor area is more than 4m² so he says it has to meet C-s3, d2 fire rating. Knauf state the wall board is A2, whats the difference ??? 

Cant afford to skim!

 

[saveasteading]

I'd have to check, but I'm 98% sure you don't need to skim.

You could ask him where it says so. I suspect he's bluffing it.

 

I went on a  fire course where they showed an actual fire test, that demonstrated that even open joints ( exposing a few mm of timber) stayed integral.  That's just btw, for your comfort. You'll be filling and taping?

[kandgmitchell]

A is good (A1 is non-combustible) F is bad - easily combustible. So an A rated plasterboard is better than the requirement for a C rated surface. Knuaf class their board as A2 which is limited combustibility probably because of the paper surface. 

Do not confuse spread of flame classifications such as these with fire resistance. That's something else. The BCO is saying your ceiling should resist the potential for a flame to spread across the surface to an equivalent standard of at least C-s3, d2. So thats C - limited contribution to fire, then s3 relates to smoke generation in this case emissions with a high volume intensity (scale is s1 to s3). Then d2 which refers to the tendency of the surface to produce burning droplets (scale d0 to d2). D2 is the tendency to produce high/intense dripping droplets.

 

So your ceiling must be better than one that has a limited contribution to fire, produces high volumes of smoke and produces high/intense levels of droplets. Well a plasterboarded ceiling will have an A2 limited combustibility rating (as per Knauf), probably has a s1 rating (emissions absent or very limited) and a d0 droplet rating (no burning droplets).

 

I can't see why a BCO should ever query a plasterboard ceiling when tested against the C-s3, d2 classification required by Table 4.1 of requirement B2. It's way better than that.

[Dee]

That's great Guys....thankyou again!

So grateful 

Don't think I've anything to worry about. I think he's just being particularly officious with me

 

[saveasteading]

12 hours ago, Dee said:

just being particularly officious with me

They don't know everything.

The fee doesn't allow much time for research.

It is easier / less risky to ask you to do more than less.

 

I suggesf you just say that you've decided to tape and joint instead.

[Dee]

8 hours ago, saveasteading said:

 

He said he wouldn't even necessarily do a site visit either!

What exactly is the point of them???

If he does it woukd be when it's totally completed, ....everything important will be hidden by then! He'll just see me exquisite taste in decor......is there a code for that 😉

 

[saveasteading]

3 hours ago, Dee said:

12 hours ago, saveasteading said:

 

He said he wouldn't even necessarily do a site visit either!

What exactly is the point of them???

Very important role. Reading on BH we hear of bad experiences with incompetent builders. There would be far more problems without bcos. These could become big issues to later users of a property. 

Then there are the incompetent self builders....they aren't on B H of course. 

[Dee]

Is this strong enough? 

18mm ply

Min 300mm either side of notch

60mm beneath nothch

16 screws all over the place!

[joe90]

41 minutes ago, Dee said:

Is this strong enough? 

IMO that’s more than enough to compensate for the notches, well done 👍

[MikeSharp01]

Glue (probably a PU would be enough - it's pretty good in shear) would help as well but perhaps too late now.

Edited December 10, 2023 by MikeSharp01
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