More Garage Headroom

[Drumtochty]

I want to increase the headroom in my garage to use a car lift. No, I do not want a pit so please do not suggest one.

I have 2.4 mtrs under the trusses and would like nearer say 3.6 mtrs under the trusses.

The garage is timber construction 6m x 6m made of 90mm x 40mm uprights with 19mm boarding and its on a 4" block wall all round. It has a 4" thick concrete floor and the external earth comes to about 6" below the block wall garage interface.

When we built the garage the contractor had to go quite deep to reach hard pan and the block walls are 1.4 mtrs high.

Now the idea I have is to remove the concrete floor and say about a further 1 mtr of hardcore and then relay 200 mm of concrete. Therefore I will possible get

3.3 mtrs clearance under the trusses.

Will the following probably happen.

Will the timber garage tend to pull the 4" wall down and at the front there will be a large hole in the wall of 5mtrs by 1 mtr that was a block wall before.

Will the earth outside the garage tend to push the walls in.

How do I stop moisture coming through the walls if they do not fall in.

[NT]

not want a pit so please do not suggest one.

r the trusses.

th 19mm boarding and its on a 4" block wall all round. It has a 4" thick co= ncrete floor and the external earth comes to about 6" below the block wall = garage interface.

d pan and the block walls are 1.4 mtrs high.

er 1 mtr of hardcore and then relay 200 mm of concrete. Therefore I will po= ssible get 3.3 mtrs clearance under the trusses.

re will be a large hole in the wall of 5mtrs by 1 mtr that was a block wall= before.

Yes, strongly so. Any underground one sided wall is a retaining wall, and must be accordingly much thicker.

Tank them on the outside with bitumen or plastic sheet. Don't try to tank the inside, it doesnt work.

NT

[John Williamson]

want a pit so please do not suggest one.

19mm boarding and its on a 4" block wall all round. It has a 4" thick concrete floor and the external earth comes to about 6" below the block wall garage interface.

and the block walls are 1.4 mtrs high.

mtr of hardcore and then relay 200 mm of concrete. Therefore I will possible get

3.3 mtrs clearance under the trusses.

will be a large hole in the wall of 5mtrs by 1 mtr that was a block wall before.

What you want to do amounts to building a pit the size of your garage.

You need to make the supporting walls round it strong enough to support the earth, the water in the earth, and the weight of the garage and any adjacent buildings. A structural engineer will be able to do the design for you, don't try and guess, as things vary with the soil type and surrounding loading such as your house walls.

Unless you are going into the side of a hill, you will also need to build an access ramp with a gradient of no steeper than about 16%, so if you go down a metre, then the access ramp will likely be 10 Metres long.

The floor needs to be strong enough so that the whole structure can almost act like a boat's hull, and it all needs tanking on the outside. You will also need to make arangements for pumping out any ingress of water when it rains.

If you are allowed to, it would be a *lot* easier and cheaper to extend the garage walls upward.

[Drumtochty]

So dig out outside of block walls. Lay some more foundation concrete s and lay lets say a further 6" block all round tied into the existing 4" block wall then tank it to stop water coming in.

Refill with earth and if that works go ahead with removing the floor and hardcore after an engineers design check.

want a pit so please do not suggest one.

19mm boarding and its on a 4" block wall all round. It has a 4" thick concrete floor and the external earth comes to about 6" below the block wall garage interface.

and the block walls are 1.4 mtrs high.

mtr of hardcore and then relay 200 mm of concrete. Therefore I will possible get

3.3 mtrs clearance under the trusses.

will be a large hole in the wall of 5mtrs by 1 mtr that was a block wall before.

[Drumtochty]

o not want a pit so please do not suggest one.

der the trusses.

with 19mm boarding and its on a 4" block wall all round. It has a 4" thick = concrete floor and the external earth comes to about 6" below the block wal= l garage interface.

ard pan and the block walls are 1.4 mtrs high.=20

ther 1 mtr of hardcore and then relay 200 mm of concrete. Therefore I will = possible get 3.3 mtrs clearance under the trusses.

here will be a large hole in the wall of 5mtrs by 1 mtr that was a block wa= ll before.

John thanks for that!

I have a price of circa =A314k to manufacture and erect a 6m x 8m X 4 mtr = below the trusses workshop plus the base say =A35k. Plus at least =A31k for= the roller door. The numbers are getting just daft so thinking of other op= tions but the idea I had will not be cheap either.

[Jeremy Nicoll - news posts]

not want a pit so please do not suggest one.

Is there a reason why you're not:

- taking the roof off - heightening the uprights & walls - putting the roof back on?

(It's an interesting mix of imperial & metric measurements!)

Although 4" concrete is presumably currently thick enough to support a car, is it thick enough to support the point loads of a car lift?

- but also have created a swimming pool which will need pumped out?

[RustyCrampon]

want a pit so please do not suggest one.

19mm boarding and its on a 4" block wall all round. It has a 4" thick concrete floor and the external earth comes to about 6" below the block wall garage interface.

and the block walls are 1.4 mtrs high.

mtr of hardcore and then relay 200 mm of concrete. Therefore I will possible get

3.3 mtrs clearance under the trusses.

will be a large hole in the wall of 5mtrs by 1 mtr that was a block wall before.

Could you replace the wooden trusses with custom-made steel portal frames? They would definitely need to be designed by a structural engineer, so not cheap.

[Andrew Mawson]

I reckon it'd actually be easier to jack the whole structure upwards in stages and increase the height of the 4" block wall accordingly. This eliminates the issues with damp ingress, stops you having to break up the existing floor, and also saves the disposal issue of the excavated spoil. If you lag bolt timbers horizontally at a lowish level to the existing uprights to brace them, it would be relatively simple to jack it up with several hydraulic bottle jacks on block at a time.

AWEM

[Drumtochty]

Thanks guys,

To answer some questions

If I put in a four post lift I need 150mm of concrete but others have done = it on 100mm like my garage slab. I suppose I could dig squares out for say =

1 mtr around where the posts go and put in 150mm depth of concrete at those= areas.

A two post lift which is my choice needs 200mm depth of concrete slab. I'm = told and that would be a new floor slab end of story.

Jacking up the garage is being considered. Either prefabricated timber pane= ls underneath or as others have suggested adding to the concrete block wall= . The use of concrete blocks would take say three or four days to dry out b= efore I could jack the garage back down on them. It only needs a strong win= d one of those nights not in the weather forecast to create a large wooden = sail I believe.

The sensible person would just put their cars into a local garage which are= both good and inexpensive locally.

With regards to putting a metal portal roof on the existing garage, the exi= sting garage supplier reckons the garage structure cannot take the extra lo= ads and in that case needs a metal shed or a block shed.

The thoughts at the moment are to get a Stongmantools 1 mtr rise lift which= would only need say a 500mm jack up of the garage and putting in prefabbed= timber sections.

The problem with that is that I would always be wanting a full size lift ev= ery time I wanted to work underneath the cars but it would be great for bra= ke and suspension work.

As I thought, removing the floor and digging down has a number of it's own = exciting features and is now well on the back burner.

[Andrew Mawson]

I recently had a section of my house re-built, and the block wall was built on the Saturday, with the wall plate bedded down that day, and the entire roof structure (hipped with a Sussex Bonnet) was built on the Sunday morning with absolutely no problems with taking the weight of the roof. The blocks and wall plate were bedded in a 5:1 mix of building sad to cement, was had very adequately gone off the following morning.

AWEM

[Nick Odell]

want a pit so please do not suggest one.

19mm boarding and its on a 4" block wall all round. It has a 4" thick concrete floor and the external earth comes to about 6" below the block wall garage interface.

and the block walls are 1.4 mtrs high.

mtr of hardcore and then relay 200 mm of concrete. Therefore I will possible get

3.3 mtrs clearance under the trusses.

will be a large hole in the wall of 5mtrs by 1 mtr that was a block wall before.

Are you in England or Wales?

When I first read this, I assumed that you were talking about commercial garage premises but your comments elsewhere lead me to believe your garage might be part of your residence in which case the current 2.4m under the trusses may have been determined for a reason.

If these are residential premises in England or Wales, you might like to take a look here:

you get too committed to a course of action.

Nick

[Dave Plowman (News)]

The name would suggest Scotland. Or an ex-pat who wishes he still was there.

[Tim Lamb]

Along the same lines...

Re-make the timber trusses into raised tie trusses by bolting additional timber to the existing and raising the ties in the region of your proposed lift.

6m width should give you ample room for anything other than a Chelsea taxi.

Somebody with more knowledge than I can give you suitable timber dimensions. If these get silly you could use *flitch* construction for rigidity.

Benefits... can be done without interfering with the existing weather proofing.

regards

[Drumtochty]

We live in Aberdeenshire. You need planning permission for a shed over 4 mt= rs in height as this would be and I have obtained that as part of a scheme = to extend the existing double garage.

This is a domestic situation and the garage / workshop is to keep me busy i= n retirement.

I have this morning after my last post had a quote for the ground works to = build the new stand alone shed and it was over =A315k plus the same for the= stand alone shed. Getting too silly.

Therefore there are now two options.

1) Put an extension on the existing 6m x 6m garage on the back end that you= drive into from the existing garage, this would be the same width but 7 mt= rs long so total length 13 mtrs. This would take a full height lift.

2) Increase the height of the existing shed and that would be about 500mm t= o 600mm and use a mid height lift with a lift of around 1m.

So the story goes on!

[Nightjar]

On 11/08/2012 00:25, Drumtochty wrote: ...

the trusses workshop plus the base say £5k. Plus at least £1k for the roller door.

That doesn't sound excessive to me, although, unless you need to get tall vehicles in and out, you could probably save by using an ordinary garage door.

had will not be cheap either.

Excavation is always expensive.

Colin Bignell

[Jules Richardson]

Or accept that it will[1] leak, and collect moisture that does get through in an internal channel around the perimeter of the structure; direct it to a sump pump, soakaway etc.

Internal walls can be finished (ply, plasterboard etc.) on standoffs so all of this is hidden from the occupants.

[1] which seems to be the case with any subterranean structure on a long enough timescale.

cheers

Jules

[GB]

I was thinking along these lines, but you beat me to it. This must be

*by far* the cheapest solution.

[Tim Lamb]

It does force the lift to be positioned in the centre of what we are told is a domestic double garage.

If this is a problem, perhaps the concept could be adapted to creating a

*dormer* along one side? Happy planners, still d-i-y able, although costly if the existing roof is slates or tiles.

regards

[GB]

If the OP is putting in a lift, it ought to be possible to add a couple of supports for the roof right next to the uprights of the lift without these getting in the way. They may well not be needed, but it's an extra thought.