I NEED to build a garage!

[Graemevw]

Hi, just registered as i need some advice about building a garage.

Ive been searching the net for weeks and have learnt alot but still have questions.

First off, im a tiler by trade. I can turn my hands to most things, including blockwork.
I am confident in my abilities to build it, just not confident in my understanding of the requirements.

It will be 7.5x4m ish.
Double doors on narrow end, single door just after half way, 2 windows in one side.

It will be close to a boundary so will have to be block. It will have to be flat roof i guess due to the 2.5m height restrictions.

What im struggling with is foundations.

Slab with built in footings, or strip foundations with seperate slab floor? I'd like it to be as draft and damp proof as possible. It wont be for cars, it will be for a couple of motorbikes in one half and general hobby stuff in the other half.

I was going to build from wood as i could have built up from a slab but being close to a boundary makes this a no go.

There is no rear access and the site will be maybe 150'-200' from the road.

All the calcs ive done seem to suggest i need around 10 cubic meters of concrete. This would have to be ready mix, and pumped due to amounts and access and is going to get very expensive!
Is there any other options?

How much could 2 people expect to mix and pour in a day? Not 10sq M i guess!

If i go seperate footings and do the slab floor in 2 parts i can do it on 3 seperate ocassions rather than all at once.

A guy at work said i could lay the foundations in bits and as long as there is re-bar it would be fine. Is this true?

Walls will be block for 2 walls that are hidden and brick for 2 that are seen.

This is my first house and it requires renovation. Doesnt even have a kitchen yet! Not alot of spare cash left so i could do with saving on the costs of the foundations if i can, hence trying to avoid pumping large amounts of ready mix.
My wife needs a kitchen, but i REALLY NEED a garage/workshop

Thanks.

 

[flameport]

There is no rear access and the site will be maybe 150'-200' from the road.

You may want to reconsider that location, since it will make it rather difficult to get materials to the site (not just the concrete either, what about the blocks, sand, cement, roof, doors, internal finishes etc.)
Presumably you want to have lighting and power in it? How far to the house?

All the calcs ive done seem to suggest i need around 10 cubic meters of concrete. This would have to be ready mix, and pumped due to amounts and access and is going to get very expensive!
Is there any other options?

No - foundations are required, and they are made from concrete.
Pouring the slab or foundations in separate bits will just cost more and delay the whole project.

Not alot of spare cash left so i could do with saving on the costs of the foundations if i can

Unless the site is particularly unusual, saving a few quid on the foundations will be a very small amount compared to the total cost of the build - even more so if you want this garage to damp proof and usable as a workshop.

 

[Graemevw]

I have 2 possible locations, along the back of the garden, or i could build halfway down the side of the garden. This would half the distance to the road.

Only about 1.5m wide side access too.

I know i need foundations, and i know they need to be concrete. My question about other options was more about how to construct them rather than alternative materials.

I expect it to take me a while, motorbike will have to live in the (unbuilt) kitchen for now.
I expect to do it all myself, as and when i can. I can hire a digger for excavations, i can rope in friends to help easily enough too.

Just trying to get my head around how i can acheve suitable foundations at an affordable cost.

So i can try and work things out, what size foundations will it need? Will this vary depending on foundation construction?

If i go with strip foundations i seem to remember reading 100cm x 40cm, is this right?
The floor would be light use so i figured say 4" of compacted type 1 and then 4" of concrete. Sound ok?

If i went with pouring the foundations and slab in one would these dimensions be the same?

I know this is the wrong way to go about it, but i'd like to avoid going overkill on the foundations (although they obviously need to be good enough) as this may need to be done by hand!

The best, easiest way would be to dig out and get ready mix pumped in but before i can work out what that may cost i need to finalise how much i'd need.

If pumped ready mix is out of my budget then ill have to find another way, no matter how hard that might be.

 

[Graemevw]

Forgot to add, it will have light, and power. It will be somewhere between 20 to 80 foot from the house.

Dimensions are very vauge at the moment as we dont live there yet, not completed on the purchase yet.
But i spend my time at night lying in bed thinking about how im going to build this.

I may be being nieve about the costs but i think foundation costs will be large compared to the rest. Im going to build it all myself. I know qualified electricians, plasterers, chippies etc so i have no need to pay any trades, even for the few things i cant do myself.

Once i get the ground works done, in my mind, it all seems like it should be pretty simple.

Famous last words no doubt!!!!

 

[r896neo]

No your right its not rocket science.

Dont built it off a raft as you'll never be able to damp proof the junction between wall base outside and inside.

Simple strip foundation will do. they only need be double your wall thickness wide then about 9 inch thick. Depth of dig will depend on conditions but will be at least 600mm often closer to 900.

Whilst bulk filling the trench with concrete is common nowadays this is mainly a cost saving measure because its so fast but if doing it yourself it'll work out cheaper to do the footings in block probably. You can bring the footings up in block on the flat to your desired dpc height and then build on up. Leave the dpc sticking out a few inches on the internal side to tie in with the floor dpm. To make it easiest have your finished floor level a few inches above dpc.

As for the floor 4 inches of MOT then 4 inch of concrete sounds fine. If you want to park a car in it maybe go up to 6 or throw in a sheet of mesh. As for the dpm leave plenty up the edges and simply fold down your sticking out dpc and lap the dpm on past it up the wall.

Obviously getting materials in is your headache. Finding a dumper/ rough terrain forklift etc to get most volume in as few trips as possible will be your main problem.

 

[Graemevw]

Materials will no doubt have to be hand moved. A pain, but i can rope in a fair few friends and re-pay them with tiling work later on.

I'd love to put a car in it, but there isnt much side access.

So, strip foundation it is then, with re-bar i assume (can probably scavenge that for free)

So i was pretty much right with the 1m depth, ill use 4" blocks but will do foundations twice as wide as the piers.

I assumed that i'd need to fill most of the 1m depth with concrete, only needing to fill 9" is a massive saving on concrete! I could probably mix that myself.

Thanks for the help.

 

[^woody^]

You could do a strip foundation down to about 750mm not 1000

Also, rather than mass fill with concrete, you can have a strip just 200mm deep and then use blockwork to bring the foundations up to just below ground level, and then have something like 4 courses of engineering bricks - 2 above ground, and 2 below.

Width wise, a 450mm trench will do, but for laying blocks you may not be able to work in the trench, so a 600mm wide trench may be needed for that reason alone - its just a case of back filling afterwards

But do your sums to see if mass fill concrete would be cheaper than a smaller strip and blockwork

Avoid doing the concrete strip in pieces if possible. Even with rebar there is potential for differential settlement and movement

If a workshop, then think about insulating the floor a bit to take the chill off the slab. Likewise if costs allow, for the walls and roof/ceiling

 

[Graemevw]

It will be insulated, it will probably also get a wood burner (a good friend is a qualified fitter).

I havent looked into insulating the slab, but i will. Im sure there are already many threads on this subject, ill search for some.
Wall and roof insulation for sure!

Ill price up the foundations now i know my options but im sure it will be cheaper doing it in block.
Maybe if access was easier and labour was costing then things would be different.

On teh subject of block, i 'had' intended on doing 2 walls in lightweight blocks (the front and one end will be brick to match house).

I have since read that these dont render well though. Is this true?
Would be nice using something light as it all needs to be walked through.

Also, the blocks for the foundation, i assume these need to be of a different spec to the main wall block?

I know nothing about blocks, although i have laid some before.

Trench will be dug with a digger and i have loads of space so wide trenches to make life easier will be no problem.

 

[Graemevw]

Been looking at slab insulation and damp proof membrane. Seems ok.

Im a little confused about levels though.

How high above ground should the damp proof course in the wall be?

The under floor membrane needs to tie into this right?

However, i dont want too big a step onto the garage floor.

I assume there is no problem with the floor DPM coming as far up the inside of the wall as i like?

As long as floor level is above outside ground, and the DPM ties into the DPC then all is good right? even if the finished floor level is a good few inches below the DPC.

Exposed membrane up the wall will be covered by the insulation anyway so wont be seen.

Just wanted to make sure i understand properly.


On the subject of wall insulation, i was just going to batten the walls, put in insulation, then board.

What about the piers though, just insulate and board between them? Or is it pointless unless i insulate 100%?

Thanks.

 

[^woody^]

Hey, were did masona's post go with that slab detail and my subsequent comment?

You naughty mods ... that could be useful as an example of how not to do things!

 

[masona]

Hey, were did masona's post go with that slab detail and my subsequent comment?

You naughty mods ... that could be useful as an example of how not to do things!

I alert the mods to take it off as I thought thats what you wanted because I can see where you're coming from regarding the dpm which is pointless info which I'm surprised the paving expert website is generally pretty good info but I thought it would be easier for the diy'er to do if the dpm was done correctly but it's misleading.

 

[^woody^]

LOL ... Ok, its just that I thought I was going mad, as I looked for the post everywhere