Trench blocks or block and engineering bricks?

[M7ATW]

Hi,

I'm considering to undertake a very small extension on the side of my house and am just considering the construction details to enable me to cost out the materials etc.

Is there any benefit from installing 300mm trench blocks instead of blocks and engineering bricks?

Is it just quicker/easier due to only laying one block or is there other benefits/negatives that I haven't thought of?

I'll be installing engineering bricks on the last 4 courses up to the DPC so that it allows for any discrepancies on the outside floor level.

Any advice appreciated.

Thanks

 

[daza1001]

Using trench blocks you will save you on cavity fill concrete. You have to fill cavity up to 225mm from DPC normally.

 

[M7ATW]

Daz - Thanks, I'm aware of the need to fill the cavity with a weak concrete mix, so yes that's another saving.

I've dug a trial hole today to try and establish the depth of the trench, but I've got a metre down and still hitting fairly loose sandstone, so looks like they might need to be deeper than I'd originally hoped.

This is one of the reasons for the question, as I'm trying to assess the easiest solution for laying purposes.

 

[cjard]

Not that concrete is expensive, but trench blocks are brilliant.. Use a shovel to lay your mortar out and throw em somewhere near straight and level. Ask your building inspector about the ground conditions as you may be removing stuff he'd be happy to put a strip found on

 

[M7ATW]

Cjard - thanks, that's the answer I was hoping for - both in relation to the trench blocks and the ground conditions.

I've never completed anything on this scale, therefore I'm a little phased by the groundworks.

I'm awaiting feedback from the Local Authority whether it falls under permitted development, then i'll be going down the Building Notice route.

I'd imagine I'll have to complete the neighbour consultation scheme which will put me on hold for a while. Does anyone know if this is required on all permitted development projects?

Thanks again.

 

[cjard]

Ground works are frustrating because you spend hours and thousands that, by the time they're complete, look like nothing has really changed.. Remember to leave service penetrations where required

There's a section of the forum dedicated to planning but the tall and short of it is you can put a single storey extension 3m on an attached or 4m on a detached house unless specifically prohibited by the planning permission that implemented the house, or by article 4 direction on your area. These sizes are doubled if you complete the neighbour consultation process. Note that a house always has an "as built" element and may have an "extended" element. If you build a new extension that connects to an old extension, it becomes a single extension and if the new part is done under PD the whole must fit within the rules

 

[M7ATW]

Cjad - Thanks again, it will be 4.2m long on a semi-detached property, so it appears the neighbour consultation will be required.

As long as the project doesn't need full planning, then I can live with a few other requirements.

 

[cjard]

By long I presume you mean deep (rearwardly projecting, measured from the rear wall that is going more rearward).. The width can't exceed half your house if it's a side extension or wraparound. There will be various bits like height restrictions, appearance. All detailed in a govt guide.. Google planning portal common projects permitted development

 

[M7ATW]

Cjard - it's to the side elevation and will be 1.5m wide x 4.2m long. I've looked on the Planning Portal and am familiar with the requirement to match materials, maximum eaves and ridge heights etc.

I know this is very small in width once you've knocked off the 300mm cavity wall and dot and dabbed the walls etc, but it's just for storage etc and will hopefully be the first DIY extension, so I can cut my teeth before starting a 3m x 3m on the back.

Thanks for all your help.

 

[cjard]

It depends then where the 4.2m starts. A side extension establishes a new side wall to the house. THe front most corner can be no nearer the road than the corner it replaces. The back corner can be no further from the road than the existing corner plus 3m (6 with NCS)

If your house is 10m deep, and yoire starting your 4.2m extension from a point 8 metres back from the front most wall, then 4.2m is within PD, as the extension will only hang off the back of the house by 2.2m.. Beware the earlier note I made about multiple extensions:if they touch, they merge in he eyes of the law

 

[M7ATW]

The proposed extension will not project beyond either existing corner - it's just going to tag onto the side of the existing house with a door opening broke out in the existing cavity wall at the bottom of the stairs.

There's no previous extensions to complicate matters.