Self build Garage.

[Bouba]

I asked this advice on another forum but got told that it is only meant to be done in a by a pro. I would like to build a garage in my garden and believe its not as difficult as its been made out to be.

I own end-terrace so all 4 sides belong to me. Please can I get advice as to how to proceed step by step.

The total area is 3 metre x3 metre only. Apex roof and total height around 3-3.5 metre.

Concrete Block or Brick. Which is cheaper?

Self mix concrete or readymix?

My garden has only 1 foot of top soil and then I hit clay. Do i really need to dig a 1 metre or 600 mm is fine.

Can i just do the digging and footings and lay block or brick few months down the line.


Single skin if using bricks or blocks and then lag it from inside.

Materials required list.

Thanks you.

 

[Bouba]

Apologies dont know why the text is in bold. Did'nt mean to be rude.

 

[limerockconstruction]

Just given the line of some of your questioning, i'd imagine that it will be quite difficult for you! I would imagine that if you don't already know which is cheaper block or brick then you should stop right now.

 

[Bouba]

Any other views please except the "do not do it" types.

 

[noseall]

600mm deep excavations are acceptable if soil conditions are unlikely to change.

Anyone can build anything, we are all human after all. However there are some things that are easier to get wrong than others. There are also some things that are more difficult to put right than others. A pro just knows how to do the above better.

You can lay the concrete and then build off it a century later if you wish, but you will need to clean the concrete off first. Laying on the conc soon after it sets gives you a nice clean base.

Do you know how to set out a building square? How to peg foundations level? Drains?

 

[Bouba]

Noseal. Thank you. This is the sort of answer I was looking for.

Please advice if 150mm deep concrete be enough or do i need more depth. Yes I can build a square using 3/4/5 but dont know what to use for shuttering.

Is there a forum or website which gives a detailed sppon feed step by step for building a garage.

My side and back neighbour have high flower beds so if i put Acudrain all around the perimetre and divert it would it help damp.

I want to build a raised slab off the ground and start the first course of brick on that. Is this possible or will i need to start the first course underground.

Thanks

 

[noseall]

It is more beneficial and simpler to build a conventional strip foundation base than it is to faff about with a reinforced slab, and will alleviate any damp ingress headaches later on.

Dig down to suitable sub soil, i.e min 600mm deep, at appropriate trench width.

Pour min 250mm concrete found's.

Build masonry up to dpc, i.e. finishing 150mm above external ground level.

Lay concrete floor on dpm to suitable height corresponding with external ground levels etc.

Build garage masonry off dpc.

 

[Bouba]

Thanks noseal.

Finally what to use to bring level upto dpc.
Engineering bricks or dence concrete blocks.

I want to use few courses of engineering bricks at the bottom and then continue with facing bricks till roof.
As it is single skin, I read somewhere I need cavity wall. This will always be garage and used inly for car maintainance purposes

 

[pred]

Underground 10 newton blocks.

As noseall says, dig out your trench, you want 600mm wide and as I don't know what your soil is like I will say1 metre deep, you want to end up with at least 200mm thick concrete strip foundation, so from the highest point of the trench area knock a baton into the trench floor until it is 750mm from the top of the baton to the lip of the trench, put a piece of timber across the trench to measure down, now using a spirit level hammer more batons in the centre of the trench all the way round every 4' or so, these batons will be staying there, they are the guides for pouring your concrete in till it reaches the top of the baton, you will need a decent rake to move the concrete about and a couple of helpers on wheel barrows, if you phone the concrete delivery with the sizes they will tell you how much you require, NB they will not hang about, time is money and they have other clients with deadlines!

The next day you'll have a trench with a good 200mm thick concrete, start building up with your 10 newton blocks, four coarses will be 900mm high which will give you your 150mm above ground level for your DPC and DPM.

When you've got that done come back.

 

[^woody^]

Why are you recommending 10N blocks for a shed? The OP will break his back trying to lay those in a trench

And a 450 trench will do for a single block wall

If the OP is not experienced, then he will have a job trying to square the walls in a deep trench

The best option would be to mass fill the trench with concrete and have 3 course of engineers - 2 above ground, 1 below. Easy to do and easy to level and square up

I can't see a point in having a DPC with single skin garage/shed walls

 

[noseall]

I can't see a point in having a DPC with single skin garage/shed walls

For the sake of a few quid and an hour or two with the trowel, i can see the point. If for example they wanted to add another skin and or convert then they have a dpc in place.

 

[^woody^]

But it wont do jack, its not about the cost. The wall above the DPC will be just as damp as below

 

[pred]

But it wont do jack, its not about the cost. The wall above the DPC will be just as damp as below

Sorry woody I don't understand why the wall is going to be wet above DPC, could you explain please.

The reason I said use blocks is because they are a lot easier to lay, asking someone to lay engineering bricks is like throwing them in at the deep end.

I said go down a metre as I don't know what the soil is like there so play safe, if he wants to reduce the depth of the trench then do it in 215mm increments and lay one coarse less of blocks, I would hate for him to go down 800mm and get cracks within 12 months if it were not deep enough.

 

[Bouba]

So if a wall will be damp above and below dpc, how does one overcome this. As I said earlier I will not convert this in a living space but after all the hard work, i would want atleast a dry structure.

What to use then. Mass concrete or dense concrete block. Are red engineer brick not good as dpc or should i use staff blue underground.

 

[^woody^]

Sorry woody I don't understand why the wall is going to be wet above DPC, could you explain please.

Its a single skin wall. That wall will be getting soaked from the rain, and that moisture will be getting to the inside face.

So having a DPC is doing nothing at all to keep the wall dry and the inside of the garage dry

In addition the DPC retains water that moves down the wall, so after prolonged rain it ends up with more damp (a line of damp) along the top of the DPC - again making the inside face damp just above the DPC.