Building a stud wall with open space above top plate (nothing to fix it to horizontally)

[wellayeman]

Hi I've been tasked to build a partition but the trouble is there is nothing to fix the top plate to as the ceiling is about 5m high and they only want it 3m high. Wouldn't be too much of a problem but the width of the partition will be about 3.5m wide and I can't seem to find any cls timber longer than 2.4m in length so I'm a but stuck as to how I'm going to build this the best way. What's the best way to join two lengths of timber together to get the strongest top plate in this situation?

Sorry if this is a total newbie question

Thanks

 

[Deleted member 174758]

For an unsupported wall you need to go to 4 x 2in CLS if at all possible as 3 x 2in CLS will be awfully "wobbly". If you buy from a timber merchant or builders merchant CLS in any section should be available in longer lengths - I had some 4 x 2in CLS delivered yesterday in 4.7 metre lengths. Some merchants carry "regularised" timber rather than CLS.

Another couple of things to consider: for a more rigid wall use a couple of rows of horizontal noggins between the joists and double up your header by adding an extra binder above it. The binder should overlap any joints on the header. Screw the frame together with 5 x 90/100 or 6 x 90/100 mm screws as screwing always makes a more rigid wall than nailing. The sole plate needs to be well fixed down to the floor - the bigger the fastenings the better (e.g. Rawlbolts as opposed to screws and plugs, or coach screws as opposed to woodscrews, etc). 400mm centres are better than 600mm for rigidity. You will need to plumb the frame up before final fixing to the floor - this will require the use of home-made timber wedges beneath the sole plate

 

[wellayeman]

Thanks for the reply. I think I understood that correctly. Just to be clear - I am also fixing vertical studs to the two walls so it will only be the top plate that is not fixed above, therefore the "frame" will already be plumb before I fix any other vertical studs or the noggins in. My order of fixing is going to be foot plate, wall studs then top plate and I will use two layers of timber for the top plate to overlap the joints caused by having to use 2.4m lengths to cover the 3.5m span. We have to use b&q/trade point for timber as far as I'm aware so limited to 2.4m lengths by the looks of it and their timber is also the "was 2x4 but now its 89*38mm" type which I am told is the same as 2x4 but just planed down?

Thanks!

 

[^woody^]

this will require the use of home-made timber wedges beneath the sole plate

That will allow the frame to rock. The frame should be flat and tight against the floor

 

[^woody^]

89*38mm

That's CLS.

The rigidity of a stud wall is more from the lining/sheathing and CLS or regularised timber won't make any difference.

You may be better off glue and screwing a single 4x1 across the top and bottom. This will need to be reduced in width if using CLS. And/or gluing the two proposed joined timbers

Boards should be horizontal and bonded

 

[Deleted member 174758]

That will allow the frame to rock. The frame should be flat and tight against the floor

I don't know about you, but in my experience floors are rarely flat and level. If the floor isn't kevel to start with and the sole plate is pulled down hard onto it without being levelled with wedges, the studs will never be plumb, because the floor throws them out. You only use wedges if absolutely necessary and you do need to use larger size fixings into either a concrete floor or a joist/beam below to keep the sole plate fixed correctly and level. Oh, and I've done enough of these to be able to say with certainty the if properly wedged and fixed they don't ever rock!

The rigidity of a stud wall is more from the lining/sheathing and CLS or regularised timber won't make any difference.

Against rough carcassing it most certainly will! (CLS has less splinters, too) As to glued joints, they aren't all that effective in a site environment because you don't have any effective means to clamp joints together whilst the glue sets and in any case carcassing timber often isn't all that straight, even regularised/CLS has defects. Glue works better on properly formed joints, such a mortise and tenon joints, or where there is a large surface area for the glue to work on, such as glueing a sheet of plywood onto a frame

Boards should be horizontal and bonded

Yes, but the way it's done in shop fit work is to glue and screw a thin layer of plywood to both faces of the wall before applying the PB, however that is quite an expensive approach (but handy if you need a full wall pattress). With the plywood cladding you can also get away with taper edge boards taped and jointed

 

[Deleted member 174758]

Just to be clear - I am also fixing vertical studs to the two walls so it will only be the top plate that is not fixed above, therefore the "frame" will already be plumb before I fix any other vertical studs or the noggins in.

Over 3.5 metres you'll still need to ensure that the other studs are plumb - two end studs alone won't necessarilly do it.

My order of fixing is going to be foot plate, wall studs then top plate and I will use two layers of timber for the top plate to overlap the joints caused by having to use 2.4m lengths to cover the 3.5m

Better by far to cut and build your wall as two separate frames, flat on the floor if at all possible, then raise them into position one by one, pack-up the lower of the pair so the tops are level, and add the binder afterwards. Trying to build a frame off the floor as sticks the way you propose is time consuming, error prone and can be very frustrating and is not the way a carpenter would normally approach the task

We have to use b&q/trade point for timber as far as I'm aware so limited to 2.4m lengths by the looks of it and their timber is also the "was 2x4 but now its 89*38mm" type which I am told is the same as 2x4 but just planed down?

Personally I'd find a proper timber merchant or builders merchants - they'll be cheaper and probably better quality (not to mention supplying longer timbers). Even with longer timbers I'd still be adding a binder to increase rigidity.

When talking about carvassing timber the dimensions are always assumed to be "ex-", so ex-4 x 2in should finish at about 90 x 44mm (3 x 2in CLS is about 70 x 44mm finished size). That's how the trade works, I'm afraid

 

[Deleted member 174758]

The rigidity of a stud wall is more from the lining/sheathing and CLS or regularised timber won't make any difference.

Against rough carcassing it most certainly will! As to glue joints, they aren't all that effective in a site environment because you don't have any effective means to clamp joints together whilst the glue sets and in any case carcassing timber often isn't all that straight

Boards should be horizontal and bonded

Yes, but the way it's done in shop fit work is to glue and screw a thin layer of plywood to both faces of the wall before overboarding with PB. Has the advantage of giving you a whole wall pattress.

 

[jks7492]

A 3m high stud wall with no restraint at the head? It’s going to be wobbling all over the place surely?!..

 

[martygturner]

I fitted a set of pocket sliding doors room divider with in a stud wall with a span of 4.1m with no head plate connection to the ceiling, . Just used the yank method, they do it all the time...make a timber beam, sandwich c16 2 x 4x2 on edge between 1 4x2's and a 6x2 planned finish for the top, just to give a little detail and something for the plasterboard to fit up to. glue and screw @ 100mm centres.

Double stack the start and finish studs, the first stud finishes under top plate and the second stacks stud finishes under the beam bottom plate, this was just to allow for fixing the beam at top side and bottom.

It supports 2 x 75kg doors for a clear span opening of 2m. As its a pocket door there is effectively no support from the studs these are just to hang plasterboard on and are just metal lath with a wood stip to get a plasterboard screw started possible 1 inch thick. It does not move.

At 3m you don't have a span long enough to do a Filch beam or a sheathed system. As your two ends are constrained all you are worrying about is the centre moving and orientating the wood in the head plate in two different planes will sort that out. If you are fitting swing doors do an I beam for any door openings , 2 4x2 with a 4x2 on edge sandwiched between.

 

[Deleted member 174758]

I get your drift you are effectively making a stiff beam at the top.of the wall, but the problem is that makes for a very thick wall

 

[martygturner]

I get your drift you are effectively making a stiff beam at the top.of the wall, but the problem is that makes for a very thick wall

Timber Stud walls are normally 4x2, the beam is only 4x2 unless you go with a 6x2 top plank to butt the plasterboard and skim to..... why would you want a bendy wall ? Who wants an office partition that shakes every time a door is closes.

 

[Deleted member 174758]

Timber Stud walls are normally 4x2, the beam is only 4x2...

Timber stud walling is anything the architect specifies. Plenty of older walls out there made from 3 x 2in, plus more midern ones from 5 x 2in or even 6 x 2in...

...make a timber beam, sandwich c16 2 x 4x2 on edge between 1 4x2's and a 6x2 planned finish for the top, just to give a little detail and something for the plasterboard to fit up to. glue and screw @ 100mm centres.

So, basically the same as a pair of 4 x 2 frames with a 4 x 2 binder on top. The 6 x 2, with an extra 1in overhang on both sides is going to be a lot more expensive. You then refer to a pocket door. Do you mean that? A pocket door retracts into a pocket within a hollow wall, which with even a 32mm thick door imies something like 150mm thickness normally

The thing I'd do is to build the wall as two frames, screwed together (not nailed), with two sets of horizontal noggins at 1/3 and 2/3 height. When the frames are fixed to the floor and a 4 x 2in binder screwed to the top and to the two uprights at either end (making in effect a 4 x 4in beam at the top) the wall would be pretty rigid. But hey, I've already stated this, and it is based on a few years experience

 

[martygturner]

Job- the beam does all the work...and no normally you don't have do a 150mm wall as the sides of the pocket are faced with metal lath faced with wood as I pointed out ...the wall itself is 100mm and takes upto a 44mm door and final thickness of the wall is 120mm with both sides encased in 9.5 board or 125 in 12.5 board...see below. If you want to do both sides these can be bussed. I would have thought with all your years you might have come across them...I stated originally that that a beam design is excellent for walls with doors in them . If I just wanted to split a room I would probably go with your cheaper option, I was just pointed out how to add an opening of any size to a room divider....and a 6 inch top plate is an architectural detail I just think its nice to finish a board to something and have a small overhang...but you are going to have to cap it someway..who wants raw board edges poking out ?