Bridging Openings

Filed Under: Do it yourself, Home repair, Remodeling    by: ITC

The way you tackle the job of making an opening in a wall or removing the wall completely in your house, depends on the type of wall it is and its construction.

A load-bearing wall contributes to the strength of the house by supporting some of its structure: a floor/ceiling, an upstairs wall or part of the roof.

A non-load-bearing wall is simply a dividing partition and its complete removal will have no effect on the rest of the house.

Inspect the floor space above it for signs that it supports the joists, or an upstairs wall. Look in the attic, too, to see if any of the roof framework rests on the wall in question.

All external walls are load-bearing and in general any wall at right-angles to the joists will be load- bearing too. Walls that run parallel to the joists are probably non-load-bearing.

Walls may be of brick, concrete blocks or be wood framed. All three types of construction are used for both load-bearing and non-load-bearing walls.

When you make an opening in a wall, no matter how narrow or wide, you must insert a supporting beam or lintel across the opening to take the load of the structure above, even if it is a non-load-bearing wall. The problem is that even by removing a narrow row of bricks or blocks to make room for the be will put the structure at risk.

For a narrow opening like a door, the bond in pattern of the bricks or blocks will tend to make the wall above the opening self-supporting (or self-corbelling) and only a small triangular section of masonry will be at risk. This can be removed, the lintel fitted and the masonry replaced.

With a very wide opening, the self supporting tendency will disappear and a wide area of the wall will be liable to collapse. To prevent this happening. you must support the wall (and sometimes the ceiling on either side) temporarily with heavy wood and adjustable props.

Openings in walls may be spanned by lengths of concrete, steel or wood. Those for fitting over small openings like doors and windows are called lintels; those for spanning wider gaps are called beams. The following are common: Steel Joist — a heavy I or L-shaped girder for spanning very wide gaps in load-bearing walls; Reinforced Concrete Lintel — for internal or solid brick external walls in spans of up to 10ft.

Heavy to lift and often cast on the job site, is the Pre-stressed Concrete Lintel — lighter than reinforced concrete lintels but not suitable for load- bearing walls, except in upper floors. For spans of up to loft, the wood lintel is used in wood framed walls.

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