Timber beam connection to existing masonry

[Ben Bord]

Good morning,

We are doing a loft conversion. Structural engineer has designed timber beams over existing windows below to carry the load of rafters and transfer it away from window lintels. In order to install this beam and achieve correct level for rafters, we will have to match the top side of this timber beam with existing wall plate. This will mean removing locally wall plate and taking off 1 or 2 layers of brick. My question is how do we fix this beam to masonry so it doesn't rotate. I have looked in Simpson catalogue and the only connection that would be suitable is the wall strap (please see attached). The problem is that this only works for new masonry wall. We don't have access to the wall below in this way as there is insulation in the cavity and plasterboard on the inside which we would prefer left undisturbed. So the only thing left is to try to screw it from the side to the masonry which doesn't seem sufficient.
Is there any standard way this is usually done?
Thank you very much for your comments.
Ben

 

[^woody^]

Why would a beam rotate?

 

[Ben Bord]

Rotate/move I guess I am trying to make sure it stays in its position. If it doesn't move, why do they fix wall plates with straps?

 

[Notch7]

Rotate/move I guess I am trying to make sure it stays in its position. If it doesn't move, why do they fix wall plates with straps?

Wall plates are fixed with straps to stop strong winds creating uplift and blowing your roof off. Or on a gable end to tie the brickwork to the roof.

 

[Ben Bord]

Ok. So are you guys saying that we should cut wall plate, remove 1-2 layers of brick, put in the timber beam over window, maybe put in few screws through into the masonry and then put rafters onto the beam and that should all hold? It doesn't seem very stable to me, but I'm no expert so I will trust your judgement.
Thank you.

 

[^woody^]

Rotate/move I guess I am trying to make sure it stays in its position. If it doesn't move, why do they fix wall plates with straps?

Whatever is fixed to it will hold it in position. The forces on a wallplate are different to the forces on a beam and so require different solutions.

Surely if you have had all this designed, then if the designer thought it was necesary to design something to stop it moving, then he would have done so. Or like on every over loft, the beam is just put there and that's it.

 

[Notch7]

Ok. So are you guys saying that we should cut wall plate, remove 1-2 layers of brick, put in the timber beam over window, maybe put in few screws through into the masonry and then put rafters onto the beam and that should all hold? It doesn't seem very stable to me, but I'm no expert so I will trust your judgement.
Thank you.

The rafters you fix to it will lock it in place. There are no lateral or twisting forces if the rafters are sitting on top. If they are fixed to the side with joist hangers that may be different, but probably solved using the correct hangers.

If you think about it really big steel beams in a lintel arrangement arent fixed in place -a fixing into masonry wouldnt do much on a 300kg beam anyway!

 

[tony1851]

If you are fixing the floor joists firmly to the sides of the rafters, that will stop the feet of the rafters from bending outwards. The load would then be acting vertically downward and the timber beam would not rotate.