The Brew Cabin

Posted: **Tue Feb 12, 2008 3:54 pm**

Hi Guys, You've got a complete amateur here:

I am currently looking for contractor to build a retaining wall to bring ground up to level, for off road parking (3 spaces) at the rear of our garden (pics below). Any help with the specifications would be really appreciated as I'm completely out of my depth here.

I've had a couple of quotes and the guy I liked seems to be a little outside his comfort zone and I really want to dot the i's and cross the t's. before getting a final written quote.

This the spec i've formulated so far(mainly copied and pasted from this site), please feel free add, take apart or tell me I'm peeing in the wind. The contractor I mentioned was talking about a 9" thick concrete block wall, would this give enough support?.

He's also humming & arghing about a written gaurantee and it would be a great help if anyone could point me to exactly what a written gaurantee would actually gaurantee, if you get my drift.

Anyway here's the spec:

Excavate and dig foundations for large retaining wall (150 mm deep 450mm wide)?
Build large retaining wall to bring ground up to level and fill void with hardcore ?
Excavate any soft spots in sub-grade as required and dispose.
Supply, lay and compact minimum of 100mm of DTp1 crushed stone sub-base material to falls and levels.
Supply and erect all necessary formwork and shuttering.
Supply and place 1 layer of PIFA 1200 Damp Proof Membrane to base. Lap joints to be taped with min. 350mm overlap.
Supply, place and finish 100mm of Class C30 mass concrete with steel reinforcement.
Include expansion joints as required, comprising full depth flexible filler board with 30mm suitable sealant to top of joint. ?
Surface to be brush and trowel finish.
Clear all site of shuttering, debris and rubble on completion and make good.

Thnx in adavance for any replies or advice.

Posted: **Tue Feb 12, 2008 5:20 pm**

you will need a hollow concrete block wall, with vertical and horizontal reinforcing rods, going into the foundation, then mass filled with concrete.
The footing will need to be wider, and deeper, and re-inforced, but a structural engineer will be able to specify this further.
You will also need to remove the topsoil. don't put hardcore straight on top, and i would also suggest a terram matting underneath.
Apart from that, i see no problems, but there are others far more qualified on here to tell you better!

Edited By dig dug dan on 1202836918

Posted: **Tue Feb 12, 2008 9:35 pm**

i have seen 225 blocks go with this kind of loading,i would opt for a 600 mm wide foundation 450 deep with L bars in the foundation spaced to come up the centre of the blocks,once the blocks are laid (a pain over the rods,i know from experience)fill the voids with a no fines dry concrete (engineer specified this last time) and away you go
this type of wall needs to have returns at one end at least to strengthen it ,so the finished wall will be a a L or U shape

we normally set out some blocks in advance and make a template for the bars in advance so they work to the holes,drilling 12mm holes through a rip of ply does the job fine
but as ddd says engineer would be able to say 100%
cheers LLL

of and if you use hardcore make sure and crush it first down to type 1 size
brick hardcore is not suitable due to voids,needs to be crushed first

Posted: **Tue Feb 12, 2008 9:36 pm**

i just looked at your profile and you are in DDD's locale :;): :;):
he rents out a lurvely crusher
LLL

Posted: **Tue Feb 12, 2008 11:20 pm**

Hey thanks for the replies.

Its a bit late now but here's my revised spec:

Excavate and dig foundations (450mm deep X 600mm wide) for footing of large reinforced retaining wall
Supply and place Class C30 mass reinforced concrete footing with L bars spaced to centre of concrete blocks
Build large retaining wall with vertical and horizontal reinforcing rods using hollow concrete blocks (215mmx440mm??) to bring ground up to level. Fill the concrete block voids with a no fines dry concrete.
Remove top soil and excavate any soft spots in sub-grade as required and dispose.
Fill void with type 1 size crushed hard core
Supply, lay and compact minimum of 100mm of DTp1 crushed stone sub-base material to falls and levels.
Supply and erect all necessary formwork and shuttering.
Supply and place 1 layer of PIFA 1200 Damp Proof Membrane to base. Lap joints to be taped with min. 350mm overlap.
Supply, place and finish 100mm of Class C30 mass concrete with steel reinforcement.
Include expansion joints as required, comprising full depth flexible filler board with 30mm suitable sealant to top of joint. ?
Surface to be brush and trowel finish.
Clear all site of shuttering, debris and rubble on completion and make good.

Is this the kind of concrete block your talking about http://www.westernblocks.co.uk/dchbtb.pdf, I'm unsure of sizes.

LLL I 'm sorry I really don't understand

this type of wall needs to have returns at one end at least

The wall is U shaped or am I missing a point here.

On a side note withh 600mmm footing and as I won't have access to the other side of boundary will that mean a gap between the wall and boundary.

There hasn't been a structural engineer involved in this, (cost,cost and cost) am I being really stupid.

Any hints about the written guarantee would be really appreciated

Thanks again

The Brew Cabin

Help with specs for retaining wall - Needs to support vehicular use