Cavity trays omitted next to roof

We are going to build a pitched roof over a porch and we omitted to install cavity trays (to be joined to the flashing later) in the cavity wall it will abut. The porch will be an enclosed area. The wall is built up to the ridge level of the porch roof at the moment and the porch has been built, just without the roof.

The picture in this page shows the cavity trays we omitted to installhttp://www.cavitytrays.co.uk/damp_products.php?id=typex

Both the NHBC and Council inspectors have been to see the work but neither commented on the cavity trays.

Is there a (cheap and easy) remedy to the situation? All suggestions welcome

Thanks

Nige f will probably rollock me for saying this but cavity trays are only useful in very severe weather conditions.
that is continuos driving rain for a substantial period of time.

i have only known of one instance where the driving rain actually caused a problem local to my area.

it may be a different story else where in the country.

if you feel that driving rain is going to be a problem then a cavity tray installation could be a wise move.

there are no cheap alternatives i'm afraid.

The house is in an area of the UK with low exposure to driving rain, the classification says:

"Sheltered, less than 33 litres/m2 per spell"
Could this be the reason why the inspectors did not comment on it?

Also, it does not appear that the Building regs demand cavity trays in this position. The NHBC guide specifies them but the inspector only insisted on the cavity trays above the windows.

The builders did put a cavity tray on the horizontal row of bricks immediately above the place where the pitched roof ridge is but the cavity tray does not follow the slope of the roof downwards and cannot be joined to the flashing. This picture shows it:




However, I do not want the above to become excuses

I`d say that is acceptable...given the exposure etc. and the fact that stepped trays need to be done carefully and using a large amount of lead and actually look untidy ..in my opinion , when they exit the brick work and flap down onto a pitched roof ..........never classed as a pedant