Advice on new front garden wall

12 Feb 2014
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United Kingdom

We're looking into having a new wall built to the front of the property and have had two quotes so far but I had a few questions I wanted to ask before we went ahead.

The wall will be 8m long double skin at about 1.1m finished height with blues on edge, supported by three 1.6m pillars. There is a relatively big Acer tree (question to come about this) about .7m away (see photo) from where the old wall was.

The existing footings were probably 100mm and were all cracked and broken from when I took the old single skin wall down so these will need to come out and new footings to go in for a double skin wall.

One of the builders suggested a 450mm wide X 800mm deep footing for the new wall with the width around the pillars being larger. Does this depth seem right? They build houses on 1m footings.

With this depth I'm sure that the Acer tree roots will come into play and I'd hate to kill it as it's very nice to look at. Could the footings be made shallower around the tree without any major issues?

We are going to have the drive block paved later in the year, would this affect the new wall at all?

Should the new wall be constructed from class A engineering bricks from the footing level upto two courses above finished ground level?

The wall will be built flush with the pavement edgings, should the wall and pillars be in line or should the wall be stepped back?

With regards to a tile crease, most of the walls I've seen look like they have standard rosemary tiles fitted with the lugs for the roof battern included, are creasing tiles flat with no lugs? And should this be a double tile crease?

We've had labour only quotes of £1180 and £1250 to pour the footings and build the walls and pillars. Does this seem reasonable?

Any advice is appreciated, excuse my lack of knowledge about building. That's why I'm here!

Thanks, Matt
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Just dug a test pit near the tree, no major roots in the bit that I excavated. The footing will end up being 500mm from the trunk which is about 150mm diameter.

At around a foot down it's red clay, will this affect anything?

Do we need anti heave footings this close to the tree?

You're over-thinking things regarding the tree. Roots wont be a problem, if anything it will be moisture extraction and related soil movement, but in these cases if anything at all it will be relatively minor and even movement not disproportionate and the foundations down slightly in to the clay will deal with this.

800mm deep foundations is nonsense. Does the builder have a clue? 500-600 or just 100mm in ti the clay will be fine and 300 wide will be too.

Bricks need to be frost rated, but whether you have engineers at ground level is just down to design choice.

Tile creases are normal clay roof tiles (not concrete ones). Nibs on the bottom row, reversed on the next one if double crease. If you want nibs both sides, then the builder need to cut the tiles in half - so more expense.

Postion of piers is design choice.

You need planning permission for anything over 1m adjacent to a highway. Have your builders mentioned that in the quotes?
Thanks for the reply Woody,

You're right I have a tendency to overthink and over engineer. I've been looking at tree root barriers all morning! would it be worth putting some geotextile material in the footings near the tree just in case? From what I've read it's late summer that any problems might happen with shrinkage, and that's in the rare case that we have a dry summer!

I did think that 800mm sounded a bit ridiculous unless he was referring to the overall depth with 2 courses below? The wall will be double skin and the piers are double brick so I thought about 400 and 700mm width around them respectively.

Ok thanks, it looks like engineerings are cheaper that the ibstocks, do these need to be perforated or solid below ground? I'm guessing we can have perforated for the top of the wall as you won't see the holes.

I hadn't thought about that with the tiles which is good info to know, from walking round our area I've seen it done about a dozen different ways. I'll get some clay tiles.

We've had three quotes now, not one has mentioned the height as on our street there are a few of similar design, however they may have had planning permission. I'll call the council later today and enquire about ours.

Thanks once again for the help.

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Ground movement wont be an issue.

The ground moves seasonally and that normal. It all moves together.

The builder has came today and dug down to 500mm by 450mm wide.

He mentioned having three courses below ground level which would make the footings about 280mm to 300mm. We're about 150mm into the red clay.

Does this sound right? Are 300mm footings deep enough?

He's dug down 500, that's the foundation depth not 300.

If the clay is firm it's deep enough
He's dug down 500, that's the foundation depth not 300.

If the clay is firm it's deep enough

Thanks for the reply Woody, I'm struggling to sleep as this is on my mind.

I'm not sure I understand, from what I've read the footings need to 150mm below for frost protection and he mentioned two or three courses below ground level which would make the concrete depth only 300mm wouldn't it?

He also found some decent sized tree roots from the Acer going under the footing, this slims the concrete down to 250mm at one point.

There are also 4 old concrete posts about 300mm square dotted throughout the footings, they finish about 200mm below ground level. Are these ok to stay in?



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A small shallower bit will be weaker but it will just bridge over if the ground is stable. My worry would be your incoming gas and presumably electric supply if present. You need to make sure they aren't concreted in by surrounding with some compressible material.
Thanks for the reply John, I spoke to him this morning and we agreed that we'd cut the posts off flush after some discussion.

We've also made the trench deeper but he didn't think we'd have enough ballast to take us up to the 150mm below mark. We're currently 300mm below with concrete still going in but not alot left.

I've put some thick pipe insulation around the gas pipe as it was worrying me also. The tree roots are pretty much touching it but I think the tree is at full height seeing as it's over 20 years old so hopefully this won't cause issues later.

If were short on the footings can 7n concrete blocks be used to reduce the amount of courses needed below ground? That was the bricklayers suggestion.

If were short on the footings can 7n concrete blocks be used to reduce the amount of courses needed below ground? That was the bricklayers suggestion.
Yes that's normal because each block is the same as 6 bricks so time saving. They aren't half heavy though.
Yes that's normal because each block is the same as 6 bricks so time saving. They aren't half heavy though.


Would they be frost proof enough though? I'm happy to go with them if that's the case.

We ended up 300mm below ground level so it looks like that's the case. Concrete level finished at 350mm.

Will the double wall skins be tied together with normal ties? And how do they join onto the pillars? I just want to verify as I don't want this wall to fail in a few years!

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Would they be frost proof enough though?
Will the two skins walls be tied together with normal ties? And how do they join onto the pillars?
You don't need a cavity wall, that's only needed to stop penetrating damp get through a house wall which doesn't apply to a garden wall.
What pillars?
A garden wall is a very simple construction, don't over complicate it.
Thanks for the reply, I wasn't thinking of a cavity just if the two skins are tied together in any way.

There are going to be three, two brick pillars spaced at the start, middle and end of the wall, which will be recessed back so that the pillars are flush with the front of the road standing proud.

He mentioned building the pillars first then joining to the lower wall to them but I wasn't sure how.

Hope that makes sense.
"Foundations" are the bits of a wall below ground level.
Foundation depth is the distance (depth) of the wall (including any concrete) below ground level.
Foundations may be brickwork or blockwork or may be concrete but are often a combination.

So as long as the builder has dug down to a suitable depth and width, it does not matter if it is concrete or brick or block, or how deep any concrete is. It's the depth of the trench that matters.

Where those roots and cables pass through the trench then they should be bridged over and if possible the concrete foundation strip would pass under them. And a suitable gap each side of the roots left.

Don't let your builder build piers and then the infill wall. It will look crap. Have him build them as one.

Have good sleep.

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