new extension and cavity trays Damp can be a major issue in the home. Find answers to questions or post your own here.

[alandyman]

Hi,
I'm planning to put a garage and porch extension on my house.
I understand I'll have to install cavity trays in the existing wall (1960s semi) above the roofline for the porch because the wall will change from being external to internal. (I do need to do this don't I?)
So I also need to do this above the roofline for the garage?

I'm keen to avoid doing this on the whole lot if possible as it'll be a lot of hard work!.

I've attached a picture of the project below.

http://img184.imageshack.us/my.php?imag ... rance01ap2

[stoneyboy]

alandyman,
In an ideal world you should install cavity trays but as you say it is a lot of work. You could just fit lead flashing above the roof and see how bad water ingress is. If the amount of water entering is unacceptable treat the wall above the extension roof with a silicone liquid - this will need re-doing every couple of years
end

[the specialist]

Well said stoneyboy - however if you use a resin based waterproofer it will last 10 years!

Aidan

[TheDoctor5]

If you type the key words of your question into our search box to the left of the site you may find the answer is already posted or is in the DIY projects section of the website. Every post goes through a monitoring process and using the search box may speed up your answer.

If you are looking for general advice on cavity trays and the like, please see our cavity wall DIY how to pages which has useful info on insulation of cavities, cavity trays and lintels and pumped cavity walls.