Conservatory help:- party wall

[Shemboa]

Hi
Wonder if anyone could help. I'm wanting to build a conservatory 3m projection. And 3.8m across my house. My house is a semi. The conservatory will leave a 400mm gap to my neighbours house. Footings will be for a 600mm dwarf wall. And then a lean to PVC on top.
2 questions I would like help with if possible.
1 is how deep with the footings need to be? They will need 2 course on top of them to take it to damp course.
The other is about a party wall agreement. Do i need one or not. I bought my house with help from catalyst housing. Who own 20%. And I have to let them know if I build anything ect. They have come back with this question.
Saying they just need to know if we do or don't. Then I can't make plans to start the work.
We are going to stick to all the rules so we don't need planing permission.
Hope someone can help. If I've not been clear on anything let me know. I've got limited knowledge on building ect.
Thanks for your time

 

[tony1851]

Just take the foundation to the same depth as the house foundation.
You won't need to appy the PWA if your excavation will not be lower than the foundation of the adjoining semi.
If you do it this way, you will save having to apply the Act and avoid having to give shed loads of money - for absolutely no purpose - to a surveyor.

 

[DIYerNOT]

Just take the foundation to the same depth as the house foundation.
You won't need to appy the PWA if your excavation will not be lower than the foundation of the adjoining semi.

I have a similar issue (although I'm in a mid-terrace and can't decide between an extension and a conservatory), but how would I know how deep the foundation of the houses either side of me were?? I know for an extension the foundations would have to be 1m so I assume the foundations for the houses would be more than that already?

Probably a stupid question....the first of many to come!

Thanks

 

[Shemboa]

Just take the foundation to the same depth as the house foundation.
You won't need to appy the PWA if your excavation will not be lower than the foundation of the adjoining semi.
If you do it this way, you will save having to apply the Act and avoid having to give shed loads of money - for absolutely no purpose - to a surveyor.

What is the minimum depth I could go do you think? If the house is a metre plus.. Could I just do 400mm? Will this be ok as long as it solid down there.
Just want to save all the extra cost of concrete an time digging ect if I don't need to.
Thx for your reply

 

[jeds]

400mm would be ok from a party wall point of view but may not be stable enough for your conservatory. If you are on clay you run the risk of movement and cracking at that depth. I would go 600mm minimum on gritty, stony clay and 750mm if it's softer workable clay. That of course assumes you don't need building regulations - in which case you'll probably have to go 900mm.