Ideas for beefing up butchered joists...

[Tim W]

Hi,

While pulling some wires, I was reminded why plumbers should never be allowed to own reciprocating saws...

I have *many* 8x2 joists with 2" deep notches hacked out (mercifully in the "correct zones" more or less, and several 4x2"'s stacked on the original 4x2" ceiling rafters with half the wood missing on the top piece (lower original rafter is fairly unscathed).

I would add that, surprisingly, this is not actually bending in any appreciable way (ie ceilings aren't cracking) and it's been like this for

30 years.

However, I don't think it would do any harm to tidy it up a bit.

I will be infilling the notches with blocks of wood so the new floorboards sit right and have something to screw into.

I might be able to swing in a new 7x2" sitting on 1" pads on both wall plates between a pair of the less good joists.

For the rest, I'm considering screwing in a number of 4x2" noggings - tight fit, big screws to add stiffness. I may also consider adding some steel plates (sort of 7" x 6" ish) screwed in across the stacked 4x2" "joists" at some interval to tie them togther a bit more.

Are there any ready made plates for this sort of job (ie would one of those "nail plate" joiner thingies add useful value) or are there any other good ideas...

Removing wood (to replace) isn't an option - it's all randomly nailed together...

The aim here isn't to meet any particular building reg or to stop anything falling down (it isn't) - merely to leave things a bit better than we found them and perhaps lessen future problems...

Ta

Tim

[John Rumm]

Adding herringbone straps can make a massive difference to reduce the amount of "bounce" in a floor. Either cut from wooden battens in the traditional way, or using the premade metal straps.

[Tim W]

John Rumm wibbled on Friday 09 October 2009 04:51

Ah - should have checked the Wiki...

has to be said that the span is 3.4m which isn't so long.

The metal doobreys won't work as I can't get underneath to fix them and the joist spacing is random - but wooden ones would be possible. I've been running the cables in the centre 1/3 mostly (partly to avoid problems from screws) so I've left the way open to do this...

I'm tempted to do it in the storage areas too (boarded 4x2") as it shoul really beef those up - though it has to be said, I can stand on a single

4x2 joist and it doesn't perceivably bend so I reckon the original wood is pretty good stuff.

That coupled with some plates to strap the stacked 4x2" joists would probably help a lot.

Thanks

Tim

[NT]

Sounds like youre trying to solve a problem that doesnt exist. A mix of 6" and 8" timber is more than enough for 3.4m

NT

[Tim W]

NT wibbled on Friday 09 October 2009 12:13

A slight misunderstanding... In some places, it's more a case of "is 4x2 big enough for 3.4m?" If it had been me packing up 4x2 with another 4x2, I'd have glued and screwed them. But, as I say, removing anything is too disruptive

I guess your mention of 6" is from the 8" joists with 2" notched out - OK that's a good point. I'll concentrate on plating and noggin up the stacked timbers.

[NT]

What exactly is the problem? 2x6 over 3.4m makes a good solid floor, even with the odd 4" bit.

NT

[Tim W]

NT wibbled on Friday 09 October 2009 17:08

The problem are the sections of floor that are 4x2 + 4x2 where the top 4x2 is cracked, hacked and generally buggered up with 2" deep notches. You see, they didn't put 8x2" joists everywhere - almost but not quite. One section is where there's a chimney - the bloke must have been flummoxed by the lack of availability of joist hangers, so he got "creative".

Only this bit is right by the door, in a high traffic area. Worth doing some remedial work IMO, even if it's a bit of a kludge.

The other section of stacked 4x2's is in an alcove with no chance of high floor loadings so I'm less bothered.

Cheers

Tim

[geraldthehamster]

No offence, but I think you're making unnecessary work for yourself.

Cheers Richard

[Tim W]

geraldthehamster wibbled on Friday 09 October 2009 23:20

Well, I have a certain amount of remedial work anyway - like filling or bridging the notches (other wise using floorboards would be impossible - they fall into some of the notches).

It's a "while I'm at it" thing - I doubt if it will actually equate to very much extra work and many of the new (1970's) timbers are warping (not as good as the 1950s wood) so bracing it up may well prevent future problems unspecified.

[The Natural Philosopher]

In which case, if you are laying a tightly screwed skin to it, do NOT worry. Under normal loads, the lover beam will be in tension, and the upper in compression with a bit of tension and compression in te vertical plane, in between.

Once you screw e.g. a chip floor on top, that takes over almost completely the function of the top part of the beam: Its sole function is then to stop the floor buckling upwards or downwards.

If you have just floor boards, its a bit more of a problem, but you can still make good by either screwinng ply over the joists firts, and then boarding, or laying steel strapping over each joist and screwing it down.

You see,

[John Rumm]

A bit of strapping here, and a few noggings there will cure a good number of ills. Generally you have the reassurance that its been there for a good number of years without issue - and that even included all the structural stuff made of of rotten wood! So in general its only going to be better at worst.

[Tim W]

The Natural Philosopher wibbled on Saturday 10 October 2009 01:49

Unfortunately my original post said no ply and no chip - just screwed non T&G boards.

I want easy access so it's boards only I'm afraid.

You see why I'm looking at tightening up the joists now...

[PeterC]

Fully agree with easy access. My neighbour has put laminate in her bathroom; I've done quite a bit of work in there and know how many pipes and cables are now buried. I can feel an angle-grinder moment coming on :->

[NT]

So there isnt a problem

NT

[Tim W]

NT wibbled on Saturday 10 October 2009 09:42

What about the bit by the door that's a high traffic and potentially high load area?

[dennis]

Steel is poor in compression, unless its substantial it probably wont do anything useful.

[fred]

In article , Tim W writes

Although high traffic, it's going to be low load (no pianos, beds, wardrobes etc are likely to be left in the doorway for extended periods ;-).

I agree with others who view it as a non problem but I know you like to do the best job possible, add (nail) 12mm ply plates linking the two joists for half a metre either side of the cuts if you feel you have to.

[Tim W]

fred wibbled on Saturday 10 October 2009 11:25

Well, the weak bit doe run along to the window where there could be a sofa with 3 fat blokes on :)

Ply plates - that's a good idea. Easy to cut (ie I could get B&Q to turn a sheet into 7.5" strips then chop saw those as required.

In fact that might be a good solution to how to fill the holes to take floorboard screws. The notches are very irregular and cleaning them up to be square will involve a lot of messing around and removing more material from an already damaged timber.

With a sheet of ply both sides, I can simply screw a 1x2" batten level with the top of the joist and supported by the ply on both sides - much easier than trying to craft custom wood patches in.

And a few herringbones or noggins and I think that will do the job.

The room is going to get more use than it probably ever has before (as a lounge it could have 12 people up there, previously it was a bedroom and probably never had more than 3. It's really a case of "why not beef it up" as the floors up anyway, it looks wrecked and the various methods described here will cost bugger all and take a few days.

[Dave Liquorice]

Yeah but 3 in a bedroom bouncimng up and down in unison.

Where's me coat?

[Why?]

Dear Tim The best way to fill the compression zone is to get a hard(er) wood folding sliding wedges (ie if it is a two inch wide two inch deep notch cut some 4 x 2 with a power saw such at an angle such that the two cheese shaped bits sliding up and down increase the width of the combination) put the thin ends of wedges in at each end in opposing sides and slide together until they meet the edges of the hole you are filling - use two hammers either side to knock the two together. do this with glue in the joints and finish off with a pin or screw if you are feeling really belt and braces about it.)

To increase stiffness I agree about the herring bone or solid strutting but is is worth it on 4" joists If you have four inch joists on top of the existing that is not good as all it is is extra weight UNLESS you add a piece of ply to the side of both and make them one

Chris