# Forum Home Renovation Brickwork  How do I block up a window?

## leverage

hi guys, 
Ive got what used to be an external window now is a window to a living room as the previous owners built a small office off the front of the house.  Ive since closed off the office door and turned it into a study nook but the window still in the middle of the wall between living room and study.  I want to block off the window but not really sure where to start.  It is approx 180high by 80 cm wide.   
The blocks have been concreted over and i would like to match the rough look it has. If i brick and mortar to match how do i support the new wall or is it simply the mortar holding it in there?  Is there some type of reo or fixing mechanism.  In my head i could potentially block it up fine but if the house moves or whatever it could crack or even fail.

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## GeoffW1

Hi, 
The window probably had or has a wooden architrave around it. Remove this if needed, both sides. You will then see across the top of the window opening some type of support for the masonry above the opening, called a lintel or arch bar. There are several sorts of these, from just a simple run of chicken wire, to a beam or bar made of either hardwood, masonry, or steel.  
If wood, it is best to remove this, as otherwise the different expansions will crack your cement render job later. You can prop the middle of the opening with a length of wood temporarily. 
The other sorts of lintel can be left there and built in, but if steel, make sure it is free of rust. If necessary you can clean that off, and prime and paint with cold gal paint or the like. 
Remove also any window parts in the opening, which will be secured to the masonry either side by some means, often big nails hammered into wood dowels. Then you have a plain masonry opening. 
Then start laying bricks to fill the opening. Just bricks and mortar is all that is needed in that sized opening, and if you REALLY want to be thorough, knock out a half brick or 2 on each side, to engage or "tooth in" your new bit of wall with the old part. Make sure the new bit is reasonably true and vertical to line up with the existing masonry. 
Plan ahead as the bricks rise so that when you get to the top, you have the right sized space to insert the final bricks above a layer of mortar, and then a space left above them about 10 mm high. This you pack with mortar, shoved in there with a trowel, or stick or your little finger. 
Now you have a brick wall in the opening, the surface of which is 5-10 mm below the surrounding cement render. It is best to fill this to level in 2 goes if it is any thicker than that. It is likely that the existing rendered edges of the opening will not be true and level with the wall as a whole, so you may have to chip or grind away any high spots around the edges. This is so the new part blends in with no obvious bumps at the join line. 
Get some render mix, or just mortar mix, mix it up, and apply it with a steel float to your new brick. Build it up to about the right level and then strike it off to level with a straight edge. Work in an upwards direction, sawing the straight edge back and forth. Fill any voids and low spots and strike off again. Allow it to set for say an hour, then finish off with a foam float. That should get you a matching finish. 
BTW, Youtube is full of tutorials on rendering, just put in "cement render". 
Cheers

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## leverage

your a legend, your post was thorough and understandable.  Just a few questions, 
- I assume theres no need to core fill any courses?
- When i render do i go slightly over the outline and onto the old render to make it match better?
- I will take a picture of the window and wall, im not sure its normal render but could be wrong, its like concrete but still quite rough. 
Thanks again, extremely helpful post.

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## GeoffW1

Hi, 
Ah, blockwork, I did not spot that, but you did say. 
Still, all is the same until you get to the very top when I think it becomes less essential to pack in mortar to all of that last narrow space. Provided the existing lintel is still there, it should not result in any settlement cracking. 
I don't think you need to core fill, it is an cosmetic infill panel only. 
As to toothing in on each side, you could probably forget about that also. 
Yes, you could try overlapping or feathering the render around the opening a bit, but cement render is not easy to feather out finely, and I think it is more important to make sure the surrounding surface is well levelled across the opening, so that you don't see any abrupt changes in level or bumps on the join line to the new surface. 
Also the more glossy the paint, the more critical your eye will be. 
Cheers

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