All Need To Know About Load Bearing Walls When Building An Extension

Load Bearing Walls and Your Extension

Before we get onto that though, you will probably have heard the builders and architect discussing load bearing and non load bearing walls.

Don’t just nod and pretend you know what they mean-especially if you think you may want to try a little bit of alteration of your own further down the line.

A load bearing wall supports loads from above funnily enough.

So, if you want to remove the whole or just a section of wall, you will need to support any loading above, unless, of course you want to recreate your very own Fred Dibnah (one for the teenagers) type scenario.

A structural engineer will have done the calculations and worked out the sizes of RSJ (Rolled Steel Joist - there, you finally know what it means!) required to do the job. These will be shown on your

Plans and your builder will follow them.

Structural Engineer

If you consider the layout of a typical 3-bedroom semi, tends to comprise a kitchen, living room and dining room.

The wall between the living and dining rooms will, in most cases, take the joists which span from the external walls. Therefore, this wall is taking a load.

It will need supporting if you intend taking it down. Don’t fall into the trap of thinking that just because a wall is timber studwork, it isn’t load-bearing.

You need to check out what’s above it. Again the structural engineer or architect will have shown this on the plans-that’s what you pay him his eye-watering fee for.

Someone has got to pay for that BMW he turns up in.

When trying to ascertain if a wall is load bearing or non load bearing, the best way is to check out which way the joists run.

If they are running parallel to the wall you wish to take down, then it’s a pretty safe bet the wall isn’t taking any joists and isn’t load bearing.

You can work out which way the joists run by lifting the carpet upstairs to expose the floor boarding beneath.

The joists will run at right angles to the floorboards. You will see the nail holes. Elementary my dear Watson.

A slightly messier way is to knock a small hole in the ceiling below and shine a torch into the darkness.

Opening Up?

Right let’s re-focus on your extension.

Like I said earlier, you might want to take the wall down between the new extension and the existing house. Will it be load bearing or non load bearing?

I hope I didn’t hear anyone say non-load bearing.

Good. So you will need an RSJ to take the weight of the brickwork above. When I build an extension, I like to finish the majority of the construction work before taking this wall down.

This has the advantage of keeping all the mess, radio noise, profanities and cold out of the dwelling until absolutely necessary.

Your builder will check the wall that is to removed for any services and cap them off or remove them before starting.

Support and knocking through.

Your builder will start by making slotted holes in the brickwork above the position of the new R.S.J.

They will go right through the brickwork to the other side. He will then insert strongboys (essentially welded plates with handles) which, in turn, are placed on top of acrow props and tightened up thus supporting everything above.

There should be an acrow and strongboy at least every metre or less of the opening to be formed.

With this all in position, you builder should the be free to remove all the brickwork beneath. As a back up, additional acrows supporting scaffold boards can be used to span the ceiling joists and spread the load further.

Right, now it’s the horrible bit.

Inserting the R.S.J.

Obviously an R.S.J. can't float in mid air-it has to be supported at both ends.

Your builder will have chopped the brickwork back to the required opening size, but left piers at each end on top of which he will have placed padstones at the appropriate height to take the weight of the new loading.

The R.S.J must have a minimum bearing of 150mm onto the new padstones which will need to have been left for a while to go off and be strong enough.

A padstone is simply a block of high density concrete cemented in position.

Some Local Authorities will accept 3 courses of engineering bricks or even a section of steel plating as a substitute.

It’s now time to bring in the R.S.J. Your builder and his team will now have to lift this length of cold, hard, unforgiving steel into position. It’s a horrible job. Be prepared for lots of swearing and cursing.

It was bad enough just getting it around the back, now they have to lift it onto those padstones.

One slip can result in broken toes or digit removal. I’m not kidding, it can be very dangerous especially in winter and where scaffolding is involved. Each R.S.J. is of different length and specifications, but if the load is too great to safely handle, lifting gear called genies have to be hired to help.

This will obviously cost more but the safety of the individual is far more important.

Levelling and making good

Once the R.S.J has been lowered onto the padstones, your builder will check his levels and hopefully find that the steel is looking good.

He will now make good between the top of the R.S.J. and the existing brickwork using slates wedged tight and pointed in.

This last step is important, as leaving gaps between the R.S.J. and the above brickwork will result in movement, and hence a wall above that will crack like an England back four.

All that remains is some making good and a hot bath for some builders with aching backs and calloused hands.