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Cutting Out New Window and Door

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Second Floor Walls

A couple of new openings need to be cut out. The first is for a new window in the side wall of the original back room. The second is for a new doorway to the under stairs cupboard.

The window opening is in a 9” solid brick wall. One of the team marks out the overall size of the opening on the brickwork outside, having consulted the drawings to get the exact position and dimensions. A single brick is cut out from the centre of the course above the opening with a bolster and hammer. Fortunately the brickwork is bedded in lime mortar so they aren’t as difficult as they might have been to cut out. However, it does mean that other brickwork is easily loosened so the work has to be done carefully.

Strongboy on acro supporting brickwork

An acro with a strongboy mounted on top is set up inside to support the head of the opening and a course of bricks across the top of the new opening is cut out. This ‘slot’ extends beyond the sides of the new window by about 9”. Another course of bricks below this is also cut out but only for the width of the window. The reason for only cutting out two courses initially is that they want to get the new lintel set first and supporting the brick work above before cutting out the rest of the opening.

Head of new window opening Steel angle supporting external brick work

On the outside, the brickwork wants to sit immediately over the window rather than having the concrete lintel showing so a concealed lintel detail is used. A galvanised steel angle spanning the width of the cut out is positioned. The width of the steel is half the thickness of the brick work and is positioned so that its bottom lip can support a row of bricks in line with the outside of the wall. This part is then made good with alternating stretchers and cut headers bedded on the steel to match the existing bond of the wall.

Strongboy propping up the concrete lintel

On the inside, the concrete lintel is positioned across the top of the opening. The width of this lintel is also half the thickness of the wall. This is jacked up tight with the acro and strongboy and the ends are packed with slate so that it is now fully bearing the load of the wall above and the prop can be removed.

Brick work knocked out Detail of window opening, concrete lintel and steel angle

With the head of the new window fully supported, the opening below can be cut out. On the outside of the wall, the guys use a grinder to cut a straight line in the brickwork around the perimeter. The central section is then knocked out. The line cut by the grinder means that the edge of the opening is a clean cut and the window frame will sit snugly against this simply needing a little frame sealant to seal the edges. You’d imagine that knocking out an opening in an old brick wall would result in a load of making good to be done. But these guys manage to do it pretty neatly and you can already see that once the frame goes in there will scarcely be any making good needed at all.

Pocket being cut in brick work Detail of opening concrete lintel New door opening ready for framing

On to the doorway that needs to be cut out for the understairs cupboard. The original access to this area was from the back room of the house. However, with the alterations, access is now required from the front room instead. The position of the new opening is marked on the wall and a pocket is cut out at the top. A prop and strongboy are used to support the centre while a slot is cut out along the top for the lintel. This wall is only half a brick thick and is plastered on both sides so a concrete lintel can simply be set over the top. The lintel is positioned and propped up tight while the ends overlapping onto the wall either side are packed with slate. The acro is then removed and, as was done with the window, the rest of the opening is cut out in a similar fashion.

If you live in the Hertfordshire area and are looking for a professional building contractor, you can get in touch with G L Smith and Sons via their website:

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Second Floor Walls

G L Smith and Sons