Retrofit Timber Structure inside Solid Brick House

[paulandfrodo]

I'm refurbishing an old School Building. It has 9" solid brick walls.

We are building an inner timber 'skin' that will

A. Take the load of a mezzanine floor above (taking advantage of the height of the School), to give us a second floor.
B. Allow us to comply with Thermal Regs
C. Give us some straight walls as the existing brick walls are a bit all over the place.

The wall structure is (from outside to inside)

220mm Bricks (Imperial)
50mm Air Gap
100mm Sawn/Treated Timber (4 x 2 at 400 centres)
between the Studs 100mm Rockwool
Vapour membrane 500g or more
Celotex / Eco Therm (to meet regs)
12.5mm Plasterboard.

The floor is a poured re-inforced concrete slab. As such we will drill through the sole plate and fix to the floor (packers to ensure level) we have a double top plate as we are putting 175 x 50 (170 x 47) Floor Joists.

My question is....

I need to fix the timber wall to the brick wall to give lateral support - especially around existing window reveals to ensure a good, solid structure.

However, I cannot see a metal product specifically for this purpose. As, we essentially need an L shaped bit of metal with a drip point at the mid-point. Or at worst, an L shaped bit of metal we can put in at an angle, ensuring any moisture runs away from the timber.

Any help or advice would be REALLY appreciated.

 

[theprinceofdarkness]

Just spent 1/2 hour googling "wall ties". All the sites were terrible. I think what you want is basically a L shaped strip, one end you screw and plug to the wall (thin edge vertical), the free end then is angled upwards a bit and is screwed to the sides of your wooden studs. I think that you will have to handle a sample to see how easy it is to bend (have you a vice and a hammer?) or if its the straight flatish ali strip type, if you fancy drilling masses of fixing holes.
Frank

 

[paulandfrodo]

Morning Frank....

Thanks for the input. I had a search around and can't see a product specifically for this problem. However, their are a few around that can be 'pimped'.

We can use a lightweight strap

http://www.screwfix.com/p/sabrefix-roll-edge-restraint-strap-bend-500-x-100mm-5-pack/85398

And screw into brick work, then offer up to stud work at an angle, when in place, use a disc cutter to remove anything sticking out.

Or we could use a sabrefix frame tie. Again, screw into brick work and then offer upto stud work. This would not need to be cut. Ok, this one from screwfix is a tad too short, but you get the idea. This is also cheaper. Whilst it looks like it might deflect, I don't think it will.

http://www.screwfix.com/p/sabrefix-timber-frame-ties-250-pack/29339

The final option, if I am spanning a large area (which I will be doing at times), is a little bit of threaded bar resined into the wall at an angle (going downwards). In the same way you would attach a plate to the wall.

I've attached pics of the above two products.

 

[^woody^]

Why does it need restaining?

If you wanted to make the frame more rigid, then make the panels up with sheathing on the back face, and then fix in position.

 

[theprinceofdarkness]

Those straps are very OTT. Most of the material will be wasted, unless you beat up the waste into the shape you want. This is actually quite good. Using the bit with the bent right angle, you will have to drill and plug at an angle so the leg that runs towards your wood is 1/2" (?) higher on the wood side of the cavity, it will look awful but it will provide the anti drip feature. The waste you can then bend at the correct angle, a right angle but slanted across the width. If you are lucky you will be able to pick up the predrilled holes. Only reservation :- In theory the cut edges will need galvanised type paint on them to stop them rusting.
P.S. Your VCL should go right under the plasterboard. have you figured what to do with your services in the wall?
Frank

 

[Doggit]

If you haven't put up the inner wall up yet, then I'd be tempted to put a dpc against the wall, then fix tanalised timbers using Torx wall screws.

 

[paulandfrodo]

Thank you for your replies.

Woody.

Due to the area we are studding against and all the odd nooks and crannies the old building is offering to us, the loss of an additional 18mm either side and cost I would prob. pref. a to-wall-fixing. Your solution however would give a rock solid wall, that I could quite happily fall against. Essentially, the main areas we will be concentrating on with this problem will be around window openings. The rest of the stud walls should be fairly good due to the proximity of returning walls, floor & ceiling connections.

theprinceofdarkness (is this an ozzy ref ?)

I've got ones with pre-drilled holes. We were looking at this exact solution. They are pretty cheap and darn sturdy. Installing running upwards towards inside will give anti-drip. We will be running electrical/data services in the walls. And warm/cold water services will be run in the ceilings and where necessary when bringing them down inside externally exposed walls (if we have to), I will put a vapour barrier between them and the outside to resolve condensation - oh, and insulate them. Equally, we might just run these in the floor within the celotex. But we will attempt to keep warm/cold services within the thermal envelope of the building.

Doggit

For the initial DPM that is under the concrete slab, we have done this and brought it 1m up the wall. I think this might be a very good 'belt and braces' idea. If we did we would of course ensure this would come down behind (on the external wall side) of the 1m DPM that is coming up from the floor.

 

[^woody^]

A timber frame won't flex, and yours will be restrained by the floor it is supporting. You don't need to fix it to the wall.

 

[theprinceofdarkness]

Lucas the car electrical people used to use the motto " The King of the road", because of the unreliability of their kit, some wag renamed them " the Prince of darkness" . I think it was used to describe Machaivelli, in earlier years
Frank

 

[Doggit]

Interesting point woody; great in theory, and very good out of the box thinking. Except real life is where some idiot leans something against the wall before the next floor goes on.

 

[paulandfrodo]

Woody, yep, after putting up the 4 by 2's with double top plate, noggins and single sole plate, it seems pretty darn solid. When we get plasterboard on, should be fine.