The first of a few flitches
A flitch repair certainly has its place within the armoury of conserving of a historic timber frame. The flitch in principle allows a greater retention of of historic material and is a mostly hidden repair, whereas a carpentry solution (if strong enough), would equate a high loss and a very obvious repair.
In this instance the flitch plate repair allowed one of the original timbers to remain in situ, in its primary location, maintaining its chamfers and stops whilst providing the structural integrity to the frame and floor. It is logical to think that if the timber was replaced or repaired then this would be adequate, but due to the large amount of timber notching, removal of structural elements the flitch is doing much more than the original timber.
A flitch plate repair can be carried out in several ways, but is essentially it is a steel beam sandwiched between two slices of timber and bolted in position to provide extra strength and reducing the timbers deflection. Or in the case of this flitch, a T section of steel with mounting feet either end.
The moulded timber in question which was down for repair was ruptured at about 1/3 span of the beam, a scarf repair would have lost 1/3 of the timber plus a minimum of 2.5D (depending on the scarf) which would not have been acceptable, nor met the loading requirements needed for the building or the floor above. The new stainless steel plate spans from wall to wall through the beam so, as well as picking up the floor load, it also serves to tie the two walls together. Something the original timber was not doing!
Reinforcing the beam with a hidden stainless steel T section allowed us to meet these structural requirements along with saving the maximum amount of historic material, yes the timber was cut along its back, but from the underside on show the timber remains historic with the tell tale signs of reinforcement through diamond pellets above the bolt holes.
The old moulded beam in the play room can now breath a big sigh of relief now this steel is in place and hopefully admired for many years to come. This flitch was the easy one, we have another to do twice the size soon, watch this space!