Ben100

Hi all, just to close the loop on this one. I spoke with my mortgage company who confirmed that I do not need a structural warranty for the extension, but they do require building regs.

That's interesting. I've got planning permission and have BC inspecting each stage, so I would think I'll be ok.

I'd think BC sign-off would be enough too. I'll give my bank a call and see what they say.

Hi, I'm building an extension to my existing house and was wondering if I need a structural warranty? The extension is large and will double the size of the existing property. I'm not looking to sell after, but who knows. I may need to remortgage at some point too. Cheers, Ben

aha, ok, so tanking for example?

Good point. A line of insulation between the slab and internal blackwork should resolve this.

The insulation vendor states they have no issue with the insulation getting wet, but I understand your thoughts on that. I was thinking the same. If I was to run the DPM on the outside of the external brick facing wall can I just run it down to lap over the footings or would I need to run a continuous DMP through the footings and back under the slab? I've seen both examples when doing some research. My preference would be to run a DMP down from the external facing brickwork and lap the footings, then another DMP under the slab and into the internal blockwork.

For the time being I don't want to drop the entire site down 375mm and I'm not very keen on having a 375 trench around the extension either. My plan is to run the two rows of blocks and DPM up >150mm past the external ground level with cavity insulation, and just have the external ground level by the door dropped with some stairs. I'll add some french drains too for ground water, but it is a dry site with plenty of natural drainage already. Also, I'll increase the insulation in the slab. Something like this (not to scale).

Yes, looks like a typo. I'm planning UFH, so I'll definitely look at adding some more insulation in the floor.

Thanks for the advice! The cladding will be timber on TF.

Ok, thanks, I'll check out the 60mm insulation with BR. This is the exact floor build-up specified. Floor type 2. new ground bearing concrete floor: New floor to achieve U-value not less than 0.22w/m2.k Floor finish TBC 65mm reinforced S/C screed separating membrane 60mm Celotex GA4000 150mm min ground bearing RC slab Well compressed hardcore. We plan to clad the TF with vertical timber cladding to as close to the ground as possible. At the moment we're planning a single block foundation. We're actually going to be 375mm below ground level. The reason for this is a mixture of design and planning restrictions. thanks!

Yes, sorry, I mean ground floor. I am considering the idea of lowering the ground all around the new extension, but this would mean having a trench all around the property or lowering the entire garden. Both ideas are not ideal...

Hi guys, I'm looking for some advice and example foundation and slab detailing for timber frame construction. This is what I have in mind so far. Foundation: 300mm of concrete (my soil type is hard ballast) Single 140mm block up to DPC Start of TF construction with 145mm sill plate Slab: Hardcore Sand 60mm floor grade insulation 150mm RC slab 65mm screed One more important detail is that the new construction is set 135mm below ground level, so the internal first floor level is below the external ground level. What options do I have here with regards to the foundation? I can see two options. Dig a trench around the building around 375mm so the exterior ground does not come in contact with the house, and maybe add in a french drain. Have a higher DPM to external ground level and add some insulation to cope with the external ground being in contact with the foundation above first floor level. Any thoughts and comments very much appreciated as always Cheers!

Wall construction is timber frame.

No, it seems to be inconsistent across the plans. Even the points at which the measuring was taken from seem inconsistent.

Yes! I have no idea why it is like this...

Looking at it close up, the architects lines simply don't look like they measure from the actual corner...

I'm going to spend another day trying to set out the plans. If I don't get anywhere, I'll look for a surveyor. One thing I've noticed regarding the drawings/plans is I get different measurements than what is listed by the architect. I'm sure there is a reason for this or something I'm missing, but I'm not sure what. If you look at the attached screen shot (capture3) of the dwg files you can see my measurements (in green) are different to the architects (in red). It looks like the architects measurements don't go all the way to the edge of the wall (capture4), which makes them shorter. Or am I measuring them from the wrong points?

Yes, good point. I’ll check with local surveyors also.

At this point I measure 100 times, mark 30, and never cut! ?

Thanks for such a detailed reply! Great advice!

Thanks all, good advice here. I’ve tried the curves method with tape, but had some issue with accuracy and spray paint. I think the lines need to be much thinner. Not sure, maybe I’m trying to be too accurate at this stage?

Hi all, Can anyone provide some advice on setting out angles for footings? I have an unusual design with some angles, with some long runs of 10m, which is causing me lots of issues. As you can imagine if I am a degree of so off with these angles I end up being > 100mm off at the other end of the 10m run. I've just not been able to get the angles and correct lengths to match up. I have been using the 3,4,5 method for checking 90 degrees, but I'm still having issues with the other angles. Do you have any advice? Maybe I can use a laser level for this, but I've not been able to find a laser level which measures angles? Any and all advice is appreciated as I've spend 2 days on this already and am stuck! Thanks! Ben

I think I'll buy a nail gun ?

Sure, no worries. I might even put a small blog together about the build.