Paul from Wales starting on timber frame extension with DPC question

[hotnuts21]

Hi all,

 

Im paul and have just started on our two storey extension to our old Victorian terrace. The house was a HMO, but we are slowly turning it into a family home. Currently has no toilet or back wall so we are living in a holiday cottage, conveniently next door. The work is a mix of trades, DIY and my project managing it.  Trying to do it on a ridiculous tight budget, but optimistic ?  I do have an Instagram account for those interested in following the development you can find it at https://www.instagram.com/ty_ni_aber/

 

My first question is about the side walls of the timber frame and the fact our neighbours property is higher. The extension walls will be going on the party wall line, however now we have demolished the party wall etc, the ground level of the neighbours on both sides will be higher than our finished floor level, this has to come from the floor level in the rest of the house, i understand this should be 6" lower on the outside than the in.

In a standard construction this would be dealt with by a cavity tray, however our extension is timber frame not brick/block and the cladding is vertical timber cladding. Obviously the cladding will be cut short of the ground, but im concerned about the higher ground on the neighbours side, whilst its not going to be touching up against the build its going to be close and rain/water run off may cause an issue. I did think about doing a few courses of bricks at the bottom and putting in some kind of cavity tray, however this would mean the bricks stick out further than the timber cladding.

Note, to the rear of the property the ground will be lower than our floor level, so its just the sides. I also live in Wales and it really knows how to rain here too!

Has anyone dealt with a similar situation before?
Thanks
Paul

[Temp]

1 hour ago, hotnuts21 said:

I did think about doing a few courses of bricks at the bottom and putting in some kind of cavity tray, however this would mean the bricks stick out further than the timber cladding.

 

You can get plinth bricks that have a 45 degree sloping top. You run a strip of lead flashing behind the timber cladding (and any membrane) down onto the plinth bricks, out and about 1" down the sloping part. This helps stops frost damage to the top of the bricks.

 

An alternative to plinth bricks is to use some slate set on a mortar bed but plinth bricks are better in my opinion.

[Temp]

1 hour ago, hotnuts21 said:

im concerned about the higher ground on the neighbours side, whilst its not going to be touching up against the build its going to be close and rain/water run off may cause an issue.

 

We have a split level house so there are similar changes in level under our house. I was also concerned about water penetration. Built a french drain...We dug regular foundation trenches and filled them with concrete then we built brick and block walls up above the high side. These block walls were tanked on the outside with a paint on rubber tanking solution down to and including the tops of the concrete. Then a sand blind and a perforated pipe in gravel were installed before back filling. The drain pipe led to the rest of the rainwater collection system. 

 

 

 

Edited January 11, 2020 by Temp