Foundations too high - Help

[Spjg1997]

Hello,

First time post. I have put my questions in bold as appreciate this is a beefy post.

I convinced myself and everyone else that I could dig and pour footings on a rear single story extension. Long story short, when the brick layer said “fill her up” I genuinely filled the footings to FFH.

The skirt damp course on the inside is therefore 150mm above the finished floor height inside but BC haven’t commented. I am installing a lapping DPM under the slab and folding it up behind the DPM skirt on the perimeter walls. Is this going to cause me any damp issues? Will I have to no nails the skirting board to prevent piercing the DPM?

Secondly, this has therefore caused me a big problem with the back doors. At the moment we are going to have a 6inch step out the back door. Which is going to look sh*te.

Is there any way I can lower the footing in the back door opening and build it back up with 150mm course of bricks and subsequently lower the ground floor level outside? I appreciate this will be cutting into the footing but technically there is nothing above it but a door opening?

I have been bo*locked enough by my old man and my Mrs so any help to get me out of this would be appreciated.

Cheers, Sam

 

[noseall]

Hello,

First time post. I have put my questions in bold as appreciate this is a beefy post.

I convinced myself and everyone else that I could dig and pour footings on a rear single story extension. Long story short, when the brick layer said “fill her up” I genuinely filled the footings to FFH.

The skirt damp course on the inside is therefore 150mm above the finished floor height inside but BC haven’t commented. I am installing a lapping DPM under the slab and folding it up behind the DPM skirt on the perimeter walls. Is this going to cause me any damp issues? Will I have to no nails the skirting board to prevent piercing the DPM?

Secondly, this has therefore caused me a big problem with the back doors. At the moment we are going to have a 6inch step out the back door. Which is going to look sh*te.

Is there any way I can lower the footing in the back door opening and build it back up with 150mm course of bricks and subsequently lower the ground floor level outside? I appreciate this will be cutting into the footing but technically there is nothing above it but a door opening?

I have been bo*locked enough by my old man and my Mrs so any help to get me out of this would be appreciated.

Cheers, Sam

Is that DPM lapping a course above where it should be lapping? Looks to me like it is...?

In terms of the floor slab - fill in the void with compacted hard core and lay a concrete slab level with the top of the foundation concrete. Lay a DPM over the lot, fit as much insulation as you can squeeze in and lay a screed.

 

[Spjg1997]

The DPM is probably 3 course too high. Thats because I have poured the footings incorrectly to FFH. I am comfortable with the build up and starting that today.

Big questions is am I able to lower the footing at the back door in anyway? It would involve cutting it with a grinder or cut off saw.

Not sure if anyone has any thoughts!

 

[catlad]

Its bound to have a knock on effect, but I would probably do it instead of having a step.

 

[Spjg1997]

Its bound to have a knock on effect, but I would probably do it instead of having a step.

I agree mate. In terms of knock on effect - all I can think of is having to drop it, rebuilt with a lower DPC and then lower the garden 150mm below that.

Anything else?

 

[noseall]

The DPM is probably 3 course too high.

What were you thinking...?

 

[Notch7]

convinced myself and everyone else that I could dig and pour footings on a rear single story extension. Long story short, when the brick layer said “fill her up” I genuinely filled the footings to FFH.

It’s a bit hard to see what’s going on in the photos, is that the concrete foundation you can see around the perimeter?

If your foundation was set too high why did the brick layer not question it?

 

[noseall]

If your foundation was set too high why did the brick layer not question it?

That's what I'm wondering.

Surely it would have been better to peck off the top 225mm of excess conc' before setting out?

 

[Spjg1997]

What were you thinking...?

It probably more the fact I wasn’t thinking. It’s a mistake I’m trying to fix

 

[Spjg1997]

That's what I'm wondering.

Surely it would have been better to peck off the top 225mm of excess conc' before setting out?

If only he had rung me to say this I would’ve gone back and chipped it myself. It was a take the money and run job. A big lesson learnt, and sadly I only realised my mistake when the roof framing was in

 

[Spjg1997]

It’s a bit hard to see what’s going on in the photos, is that the concrete foundation you can see around the perimeter?

If your foundation was set too high why did the brick layer not question itI’m considering seeing if I can implement a step foundation at the back door?

Yes that’s the foundation poured to FFH (in error). I’ve dug down 500mm and am just about to building it back up with type1, sand, slab etc.

I am going to chip out the footings that stick into the room enough to be screeded up to and then most of it will be concealed by kitchen unitsw etc

Updated design is attached.

Big problem is the back door opening, I’m wondering if a retrospective stepped footing can be implements at the back?

 

[endecotp]

Is it the back door we can see in the photos? It seems to have two courses of bricks over the footings. I don’t see why you shouldn’t remove those. You would need to bodge your plastic around the corners.

Is there an external skin of brick? Why is the rear wall studwork and the others blocks?

 

[Spjg1997]

sorry the stud work is a temporary door to keep the rest of the house secure. That is where the back doors will be.

I didn’t think I could fit a back door directly onto the footings?

 

[Notch7]

Yes that’s the foundation poured to FFH (in error). I’ve dug down 500mm and am just about to building it back up with type1, sand, slab etc.

I am going to chip out the footings that stick into the room enough to be screeded up to and then most of it will be concealed by kitchen unitsw etc

Updated design is attached.

Big problem is the back door opening, I’m wondering if a retrospective stepped footing can be implements at the back?

I’m a little confused by the floor make up in the drawing…..have you omitted the screed layer?
Also is there a reason you have you put the insulation at the bottom?

In regards to the foundation, I would be concerned about the damp arrangements, usually the cavity extends 3 courses below DPC which means any water or damp build up runs down to the bottom, well below internal floor level, screed and skirting. You might be able to a oid any problems provided you pay close attention to the DPM detailing.



I can’t see why lowering the found at the front will cause a problem but you need to be careful where on the damp proof detailing where the foundation steps

 

[Spjg1997]

Thanks, Notch.

The drawing was done by a friend who is a QS to scale floor to ceiling height.

The insulation will sit on top of the slab and the underfloor heating will be covered by a liquid screed.

In terms of the DPC, I was going to cut the foundation down and lay 3 courses of bricks back up with the DPC sitting between the top and second row. The DPC will lap under the DPC in the remainder of the block work. Rough sketch below, black line is DPC.

I would then drop the floor in the garden, install an ACO drain that runs into a soak away and a weather shield on the back doors so anything that comes off the door runs away from the house.