I often hear of people putting accrows under first floor joists that run into a wall in order to support the upper part of that wall. But is that a sound way of doing it? How do I know that the brickwork sits directly on top of the joists, there could be a gap between joist top and next course of bricks?
propping first floor joists to prop up wall
- Thread starter rsk1
- Start date
Sponsored Links
If there is a gap, it's generally very small; most joists in older houses are usually the depth of two bricks.
Its a useful way of supporting the inner skin.
Its a useful way of supporting the inner skin.
D
Deleted member 174758
It depends on the brickwork, the joists and the amount of wall you are removing. Personally I don't like doing it because on old buildings you can never be sure how far into the masonry the timber extends, nor how sound (or rotten) it is, or how good the masonry is for that matter. If joists are going to rot anywhere it's always at the ends. We tend to use Acrows with Strongboys on smaller jobs, like these examples (culled from the 'net):
On bigger jobs it tends to be Acrows with RSJ "needles" that are used:
On bigger jobs it tends to be Acrows with RSJ "needles" that are used:
On one of my joists i reckon i can feel a 10mm gap. It might only be small, but if there's a gap then the bricks are not being directly supported. If they were to drop, and close that gap, that would be bad. Wouldn't it?
Sponsored Links
D
Deleted member 174758
One only, it shouldn't be an issue. If it were 3 or 4 together it would be. Timber wedges/packers could be used to block-out the gap
Example of work where the inner skin is supported off the floor joists, in turn supported by a plank and props. The outer skin is supported off strongboys, and the beam to be installed is at the bottom.
Ever since BC and architects started getting their knickers in a twist about air leakage and heat loss regards joists being built into walls and then thrusting build-in hangars upon us as a remedy, I've often wondered how these would work in a propping situation as we are discussing presently.
D
Deleted member 174758
I think I'd rather not find out! The SE has thrust those things at me on a number of jobs in recent years and I'm now really wary of them on old buildings (newish stuff less of an issue).
what things to check? what precautions?
That's the thing, if you don't know then you won't know.
Generally, it's about looking at the condition and layout and deciding how many props, where they should be placed, is the wall going to self-support between the props or is precautionary wedging required. Whilst a collapse is unlikely unless totally incompetent, the difference is in how much wall falls out between the props and how much making good is required. And if you can't get in to properly pack any wall that drops, then the wall above will drop slightly afterwards and crack all the plaster.
This is what can happen when a long-span beam is inserted, caused by deflection of the beam. The tell-tale step-cracking usually occurs at a weak point, such as below a window. In fact, it's not that serious and isn't a major structural concern.
In this case, the walls were being re-plastered anyway, so no harm done.
In general, cracking above the level of the beam is rarely a structural problem; if cracks appear below the level of the beam, alarm bells should
start ringing.....
In this case, the walls were being re-plastered anyway, so no harm done.
In general, cracking above the level of the beam is rarely a structural problem; if cracks appear below the level of the beam, alarm bells should
start ringing.....
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
