Raising ground level against garage wall

[ThePistol]

Hi,

I have just started a project to put in a patio, and then re grade the remainder of the garden that slopes quite badly back to front and left to right.

I am going to build a sleeper wall across the back of the house, but the garage borders the garden on the right hand side. To get the level I need, will mean increasing the height on this side quite a few brick courses above the dpc for the garage.

Before I commit to building a wall down the side of the wall along the garage to avoid this, is there any way of safely building up the earth against the garage without causing damp issues? I was thinking of a string waterproof membrane or similar, but I suppose that still won't let the bricks breath?

I suspect the answer is going to be that I can't do this, but just wanted to check before spending the extra money and losing some of the grass, if I don't have to!

 

[John D v2.0]

Yeah you can build up if you run a bank proof membrane from lapped under the dpc up to two courses above the ground level.
That way the wall is protected from the damp ground.
You do have to make sure the membrane doesn't get damaged though, but probably less critical from a garage as long as there's no timber as it's not a habitable space.

 

[r896neo]

Is it a cavity or single skin wall? How high do you plan to bury?

 

[ThePistol]

Yeah you can build up if you run a bank proof membrane from lapped under the dpc up to two courses above the ground level.
That way the wall is protected from the damp ground.
You do have to make sure the membrane doesn't get damaged though, but probably less critical from a garage as long as there's no timber as it's not a habitable space.

Thanks

Is there anything in particular I should look for in choosing the dpc to make sure it's durable, other than just not getting the cheapest one?

Sorry to thick, but what exactly do you mean by lapped under the dpc?

And is there anything in particular I should be doing to fix it to the wall at the top, to stop water getting behind it?

 

[ThePistol]

Is it a cavity or single skin wall? How high do you plan to bury?

It's single skin. Plan is to build earth up about 50cm, which would make it approx 35cm above dpc

 

[ThePistol]

Is there likely to be any issue with the weight of the built up soil against the single skin wall? From current ground level the should be about 70cm up the wall?

 

[r896neo]

Yes there is to be honest. thats why i was asking about the wall construction. if this was a free standing wall 70cm of soil would have it over in no time but because the garage has eight on the top of the wall in terms of a roof and returned corners it is stronger by a distance than a free standing wall but it is still only 4''.

I would say the risk is quite real but hard to quantify, can you post a sketch of the area including the size of the garage any piers in the garage wall and direction of any roof trusses/ rafters

 

[ThePistol]

Yes there is to be honest. thats why i was asking about the wall construction. if this was a free standing wall 70cm of soil would have it over in no time but because the garage has eight on the top of the wall in terms of a roof and returned corners it is stronger by a distance than a free standing wall but it is still only 4''.

I would say the risk is quite real but hard to quantify, can you post a sketch of the area including the size of the garage any piers in the garage wall and direction of any roof trusses/ rafters

The picture below shows the side in view of the garage - the built up level would be approx 2.3m down the side and then across the rear. Overall length of the garage is approx 6.7m

The garage is double skinned for a section in the middle, and each of the rear corners

 

[r896neo]

If it was my own I'd go ahead but if it was a customer I would recommend on a separate wall.

Depending on how the footings were done you may be lucky and have room to build a second skin on the edge with a small 50mm cavity between. This would be an easy way to make it much stronger and more secure waterproofing.

The other option would be using some scaffold planks or 6x2s to spread the load and protect the dpm. Although obviously not as good as the wall.

I don't really think the strength of the wall is an issue given the double skinned sections and returned corners.

A ventilated cavity is the most secure way to keep the wall dry although as its only a garage some rolls of dpc should be enough.