Window & door replacement with a cavity wall.

[Stubbsk]

We want to replace our backdoor and adjacent window, I've attached an image of the current setup.

We are thinking about french doors, perhaps with a side panel to allow the doors to open wider as the outside yard is quite narrow.

The initial quotes I have received sound crazy, along the lines of £2-3k, tell me if I'm being a cheapskate?

I know there are some great suppliers available online, prices around £700 for what I want, but I'm a bit reluctant to take on the work myself without first getting to grips with the following.

Removing the small brick wall below window
There's not much masonry to remove so I'm happy to attack it by hand but:

• Is it possible to get a clean'ish cut with the remaining wall? Perhaps drill through the half bricks every inch or so and knock them out by hand, and finish with some render if it's a bit dodgy? (External masonry is painted white and far from perfect anyway)
• Or does this really require specialist power tools to avoid damaging the remaining wall?

Exposing the wall cavity
The current frame appears to be set into the cavity wall, but the UPVC will be sized to the masonry cavity and set into the outer brick leaf right?

• So would I simple have to insert thermal insulation board into the cavity, and perhaps some expanding insulation foam?
• Then would it need to be capped with a fascia, or plastered if still visible after installation?
• Would weatherproof flashing have to be added?

Most the guides online pretty much just say to use some packers to get the frame level and then screw it in, add trim and seal, done! So any advice or even dissuasion would be welcome.

I'm not ruling out getting a pro in, but at the very least I want to know what needs to be done.

Thanks!

 

[Gazman16]

Pretty much that, Only scanned it quick but only 2 things I noticed you missed
1. Making good the floor/threshold
2. Building control sign off (around £200) or Fensa sign off

Unless your in London that a bit expensive. I would say a £1500-2k job mainly depending on sidelights or not

 

[Stubbsk]

Thanks Gazman, that's reassuring.

1. The floor should be fine, just need to match to the existing painted concrete.
2. I'm aware of the Fensa sign off, although I had read that it was a bit cheaper, so I guess I need to contact the local building control first.

I've just come across 'Cavity closers', and they're good to just screw the frame into right?

Although would it be acceptable to sit the french doors closer to the front of the exterior leaf, say just an inch recessed, so that the door can open wider? Or would this look terrible and allow water ingress?

 

[Gazman16]

Hello

No you wont be able to fix to cavity closers as they have no strength.
Ideally you should be at least 30mm in from the exteria and the inside of the frame should cover any vertical DPC or be a little in past the bricks to prevent bridging the cavity

 

[Stubbsk]

OK, so...

Run dpc over the outer leaf and fold back into cavity to stop damp bridging the plasterwork.

Fill cavity with insulation board or cavity closers (a touch of expanding foam if necessary).

Level sill with packers and set with silicone (Any special tips for low thresholds?).

Level frame with packers, and screw frame directly into the outer leaf or use batons to attach it to inner leaf.

Toe and heel glazing and fit beading.

Seal with silicone (Also came across some interesting expanding tape...), add trim if the gaps warrant it.

Will require building control to sign off if we knock out the little wall, plus license to alter from Freeholder