Use of glide shoes in truss roof

[FrogParty]

Constructing a new roof with raised tie trusses to make space for an attic room above 1.5 story walls. The truss manufacturers have specified using glide shoes to attach the truss to the wall plate. Using these does it mean that the truss will always be free to move horizontally on the wall plate? Or are the shoes fixed in some way once the tiles are on and the initial flexing done? A bit concerned about the roof moving around (or the walls cracking).

BTW using trusses rather than a cut roof with ridge beam as can't see how to get a 10m beam on site let alone lift it.

 

[chickenlips]

The use of Glide shoes on a raised tie roof truss is basically to stop the truss pushing your walls outwards.

The glide shoes them selves are a 2-shoe, the shoe part is fixed down to the wallplate and then a metal plate is fixed to a horizontal cut in the truss and the truss the sits into the shoe. All are nailed to each other, however the nail holes in the shoe where it is fixed to the truss are slotted and is where the movement is allowed. It is only designed to allow upto 15mm of movement which takes the lateral force from the truss off the wall its sat on.

http://www.strongtie.co.uk/products/type.php?typeID=51&familyID=5

These shoes are an important part of a raised tie roof.

You would have more to worry about if they are not used.

 

[FrogParty]

So that's how they work. I was wondering if it was just a matter of letting the roof settle with the tiles on (and deflect a bit) before fixing it. You are right, better the truss move a bit than stress the wall.

However now I am wondering how a moving roof structure, even just 15mm, will impact my attempts to make the house air tight? Butyl tape can accommodate normal settling of joints, but not sure about a 15mm shift. One reason for having the raised tie truss is to avoid the impossible job of making an attic truss with dropped bottom chord air tight. Just how much does is this kind of structure move compared to a normal fink truss roof?

 

[chickenlips]

I cant see any problems with air tightness with a raised tie truss. You wouldnt see any physical evidence of movement in the roof even with it fully tiled.
The roof could move over time, ie after a large snowfall, however it would be minimal that there would be no obvious signs. Certainly none that would pose a problem.

An stub (bobtail) attic truss would be just as easy to make air tight, as long as the bottom chord of the attic is built into the blockwork and the end verticals set in so that it can be filled between the centres. However you wont get the same usable space with that of a raise tie roof