Cutting insulated render

[phatboy]

We had our house insulated early this year.

We replaced a couple of windows at the same time and so pushed the windows to the outside edge of the blockwork, and let the insulation form the entire outside reveal.

Now, a few months on, we have decided to replace the remaining windows (A bit more money became available). I obviously want to push these also to the front edge of the blockwork to remove the cold bridge.

The easy option would seen to be cut back to where the blockwork ends and tuck the windows behind requiring no additional work to the EWI, but a better option for getting the windows well sized seems to be to cut the front face of the insulation to the original window width, and then form a new reveal. Can this be done with no bead there, or is this likely to end in an ugly mess?

Thanks
Tim

 

[vinn]

Have whoever did the original work return and quote - DIY messing up on detail like that could result in damp reveals for the next 10 yrs.

 

[phatboy]

Have whoever did the original work return and quote - DIY messing up on detail like that could result in damp reveals for the next 10 yrs.

Oh don't worry I will be, was just wondering if it was even a possible thing. Can it be cut back with the required accuracy or does it break up was my main concern.

 

[phatboy]

I haven't progressed this yet, but if anyone can advise it would be appreciated.

The original installer is no longer around to do the work, but I will be getting someone who knows what they are doing in.

I just want to know if what I want to do is possible or a bad idea.

Also, how would one cut the render? Would the right blade in a Fein type tool do the job?

 

[Doggit]

Pictures would help, but how thick was the insulation, and what render and top coat was used. On a general baisis (not knowing your specicif setup) you could cut the render with a diamond blade on an angle grinder, but you then need an angle bead to reform the corner, so you'd then need to re-render the top coat on the wall, and then redo the top coat again. All this will depend on where you can take the render to. On the job I did last year, I set up a break between the upper and lower floors so that any painting or maintenance could be done if necessary.

Can you fit the windows from inside, and then make good. If you can, then go for the easy option. You'd carfully mark out where the window was going to go, and also use a multicutting tool to get you a clean line, then fit the window to that line, and finally silicone the joint.

 

[phatboy]

Thanks for the help.

- Insulation is 90mm thick (less in the reveals as shown)
- Boards were Kay-Cel, base coat I am unsure of the make (It was French), and the top coat was Parex 534 Sand Fine

Hopefully the photos help. The ideal solution in terms of biggest windows is to cut back to where the sills (They are fascias) are, and re-form the corner there. Can this not be done without a bead? I thought as the render would have some strength, it could be rendered up to as the new corner? This could be nonsense, but would be good to know why.

The other method sounds a lot easier and probably what I will end up doing. I have some round carbide tipped cutters for my Fein tool, and can cut 100mm back from the front edge carefully, and then the window can get slotted in via the inside - the reveal inside will need re-plastering anyway so any damage past the bead would not matter.

Before I go for the easy option, I would want to rule out the harder but ideal option, or it would forever bug me that I'd been lazy.

Thanks
Tim

 

[Doggit]

I'm going to stop and pause a minute Tim. Having gone back over the post, I now see that part of wanting to move the windows outwards, is to reduce the cold bridge, but how bad is it; do you have any cold spots around the windows, and have you put an IR themometer on them to compare the difference.

If you're happy to replace the windows to their current position, and can carefully extract them from inside wthout damaging the EWI, then unless the cold bridge is bad, I'd be temped to replace as is. But even if you were to move them further out, I still wouldn't go as far as the edge, because as Vinn has pointed out, you risk a weak join between the window and the insulation that may not have been fixed securely to the wall. And you don't know how they fixed the reveal insulation to the wall, and you could well find that you've got a thin strip floating about. You might get away with fixing to the edge if you were to superglue a trim to the window frame, and then silicone it to the EWI, but it's a bit of a risk.

And I'd consider this to be the sensible method, not the lazy one.