Make That Room Bigger With a Structural Knockthrough

If you need to change the layout of your home then making a structural alteration to open up a wall is great way to go. The wall you want to open up though will need to be assessed to check if it supporting any other loads.This may be a brick load or even the floor timbers so it will be necessary to do a few checks first. A typical design of a structure could have twin reception rooms, (rear and front), with the rear room joists usually running from the spine wall (the wall you may be opening) to the external walls. The front room joists in turn, may run from the same spine wall to the front external wall of the dwelling.

Any wall that is bearing the weight of joists is therefore load bearing and will have to be supported prior to any major alterations undertaken. Typically this would be done with the use of acrow props and timbers ‘needles’ or steel supports called strong boys to take the load whilst alterations are underway.

Some loads may not be from masonry by the way, they could be from timber partitions above the wall you want to take out. In the same fashion the load must be supported both before and after any alteration is taken out.

So OK, you've made the opening and the structure has been temporarily supported. This is great at the moment but nobody wants to leave ugly looking steel props in the middle of the room forever so it will be necessary to provide a more permanent support method. This structure will need to be supported by using a lintel which may be of either concrete or steel construction depending on the engineers specifications for the job. A structural engineer will be able to help you choose the right support for the job. Never guess and think you know if you are not entirely sure! Structural engineers are paid to calculate loads and will save you a hell of a lot of money if you get it wrong and calculate incorrectly.

You will need to inform the local building inspector that you are intending to carry out work to the property who will be happy to advise on ensuring the alteration is to current standards. Building regulations is required for most structural alterations so you must make enquiries before commencing works.

Before taking any masonry away, mark out the opening in the wall that is required. Use a hammer and bolster to remove any plaster on the wall. This way you will know exactly what you are taking away and also ensuring there are no hidden pipe or cables that may cause an obstruction. You will want the new RSJ or concrete or steel lintel to rest on a minimum of 150mm bearings so make provisions for this when marking out. After the structure is propped and secure you can start the opening by using an angle grinder at the openings boundary or by using hammer and bolster.

Any debris in your workspace should be cleaned and removed to ensure you are unobstructed in any way. You will now want to prepare for fitting the new concrete or steel lintel so ensure you have enough helpers to lift the lintel in place and that you can do this safely. Some scaffold boards spanning trestles offer a safe way to do this. Bed the lintel onto a stiff 3:1 mix of sand and cement sitting on concrete pad stones. Pack up the lintel with slate afterwards to ensure it is tight to the masonry above.

Leave your support props in until the next day to let the mortar set. Only after this can the props be taken away and in doing so, fill in any holes you made for the props with bricks and point up and slate if required. All you need to do now is make good the plaster work afterwards. Make sure the local authority building inspector has seen all works etc, before re-plastering.