Search the Community

I'm building an extension (basically corridor) between my house and a detached garage I plan on converting. The trenches at 600mm wide leave just a small strip in the middle. Aside from the cost of concrete, is there any reason for this to be 2 trenches or could I just excavate the lot to the levels specified by BCO and fill the whole thing with concrete? Blue lines mark the inside of the trench

Hey Guys, Im a Uni Student studying ATD, was wonderings if anyone would be willing to have a look at at some drawings I've produced, Im sure they have lots of errors and I was hoping to minimise them, thanks for your time and any help advice, is much appreciated. The First Detail is a Curtain Wall Foundation Detail, and im getting very confused with Weather proof membrane's. The Second Is my attempt at a parapet detai between the Mansard floor and second floor I know I need to somehow include a gutter which Im also stuck on. If you have any queries feel free to ask, hopefully managed to upload to in the right forum Cheers

I'm building a small extention which will be a link between the main house and a detached garage. The garage sits ~45cm higher than the house so the foundations have been designed to be stepped. When it comes to building, does it make sense to cut the trench directly out of the concrete patio in the picture below and dig down or to completely clear the site and then dig the foundations? My thinking is that by removing less patio it will have less chance of collapsing but would be grateful of opinions. Blue lines below show the path of the inside walls of the extension

Hi All, I was hoping that I would be able to get some friendly advice which would help us decide on a sensible solution for the foundation design on our self build. During the planning phase we had an investigative ground survey, The report which was very extensive involving 6 piles drilled to various depths of 4.6 to 6.9m over the site, the soil was then tested for quality and the holes then monitored and tested for subsidence and water content over a 12 month period. The results of the test were that construction could be permitted but it was highlighted that some ground movement to the top 3.5m of superficial soil had moved down the slope during the test (6mm during the year of this test). In regards to foundation design the report summary recommended re-enforced deep trench foundations or a re-enforced concrete raft with a lightweight timber frame structure. After getting our planning approved we approached a structural engineer who reviewed our plans and report and also spoke with the ground investigation company to discuss the report before visiting the site to assess the project. Their recommendation was to having a piling solution due to the area and the work involved. For reference the property is a 10m x 10m square, and we are intending to go brick and block now we are having a piled foundation. Our site is sloping around 14-20 degrees, but the build will be on level ground so we will be cutting into the slope and installing a king post retaining wall behind the house to hold back the soil. There is already a log retaining in place which we will replace with something much better. It has held without moving for 10 years but as it's softwood it's now rotting away. The plot is also in a world heritage site with a history of coal mining so the ground is generally poor in our county. Planners and engineers are very wary in this historic area due to many period properties subsiding due to the ground conditions, sloping sites and traditional construction methods used in the older buildings. On the recommendation of the SE we approached several piling contractors for advice and quotes. The first company recommended and quoted for 35x 150mm driven piles driven to a depth of 5m. We were very happy so we booked him, he then supplied us with his structural engineering design but last week called up to say he couldn't do the work as he had spoken to another contracter who had worked in the area and said we needed augured piles rather than driven which was something he didn't do. I then went back out looking for a new piling firm and spoke with another contracter who was familiar with the area, he had actually done the piling for a build in the same street 10 years prior. He recommended that augured piles would be needed due to the ground conditions but his quote never transpired which was a shame, likely due to being so busy. I then spoke with another company, this company seemed like a really good team, really helpful, loads of positive reviews and a great website with lots of videos and photos of previous work. After sending them all the information they quoted for roughly (35x 150mm driven piles driven to a depth of 4m) , the quote was really competitive and I called them to discuss it. I mentioned that another piling contractor had recommended augured piling and said driven was not an option for this site. His reply was that they felt that the project really didn't need it? They also said following a site visit their structural engineer would make another SE plan for us and before that they would send me an additional quote which included heave protection and augured piles so at least I had a cost for both. The revised quote showed pre-augured piles down 2m. But didn't mentioned fully augured? Just augured. I then approached another company, after looking at the ground report and plans they said that driven piles would not be suitable and that I was going to need a more substantial piling solution. They quoted for 18x 300m augured piles to a depth of 12m. This was around £10k more than the driven piles quotes I had received from others but it's also the most heavy duty solution for the job. It seems we are going for a piled solution for our self-build but with all the different information we have we are having a hard time deciding on the most sensible choice, it would be great if anyone with experience in this field could give us some advice on what way to go. The information we have summarised: 1. Quote for 5m 150mm driven piles - But then said he couldn't do the job 2. Said we needed augured piles, driven no good - Quote never received. 3. Quote for 4m 150mm driven piles, but did an additional quote for pre augered piles with driven should it be need once's SE calcs done. 4. Quote for 12m 300mm driven piles. Many thanks, Edd

I have a large concrete base at the bottom of my garden which is approx 40m2. I would like to build an outbuilding made of bricks at the side and breeze blocks at the front and back. I would also like to build a cavity wall to ensure the building is well insulated. When looking at picture IMG_8756 on the right hand side the neighbours garden drops down significantly as can be seen in IMG_8758. There is a small single wall that has started to lean to one side. How would be the best way to deal with this? Would you recommend removing the single wall that is leaning over and replacing with a retaining wall? I would appreciate any advice. Also happy to provide more details if needed.

I am in the process of final bits of design on my self build garden office. However I have hit a conundrum and can’t seem to find any advice online as to how many concrete blocks plinths I need for my foundations. The building is to be made from timber as you will see below. How many concrete block plinths to support the base? and how far should each be spaced from each other? My building is: 4211mm x 3188mm These are the two options I was playing with. One with more blocks is what I had before watching a few videos and the one on the right is what I'm now thinking... if it'll hold up! It's just for an office / play room so doesn't need to house extremely heavy equipment. Any advice is greatly appreciated!!

Hi I am starting on Selfbuild Journey. We recently bought a banglow built in 1960s on a very clayee place with existing foundations between 400mm and 1m. There has been no movement/cracks. Good old days..... but it wont pass the building regs these days and we want to build on top. Hence, starting again is the option we are seriously considering to future proof the house to some extent. The existing banglow is c180sqm and with extension we can go to 225sqm plus if we build on top the first floor and the loft, one can see the expected size. This is a great forum and it has been very helpful so far and now I want to start active conversation with you guys who have been on similar journeys. Is there anyone who can share the excel spreadsheet for the cost estimation. It will be a self managed project with core skills arranged with each of the skilled trade. I read somewhere on this forum about Abbey pynford for foundations involving Piles. They have been contacted and yesterday the ground investigation work was done (expect the depth of piles to be around 10/11m with slab and the void to allow for the clay movement. That would a significant spend. The reason I am describing this as an experiment is as I want to test getting material and fit out outs from manufacturer and the scale of the project is such as that in my experience manufacturer here or in Europe/China will happily provide the requirement. In other words what would be the bare cost of a house build taking all profits element within the supply chain and building contractor out. I am just keen to find that out as the build cost per sqm does not work in my head. I want to know the real breakdown. So procurement is where the true experiment sits. I have some contact in China supply chain so any procurement from China should not be an issue. My plan is ensure the structure is all based on BBA approved items so that it qualifies for the warranty. Key steps I have outline in my plans are as follows and I am expecting different skills are required for each of the key stages hence would source these: Surveys / planning work QS costing Warranties Procurement Foundation / ground drainage /Subfloor Underfloor heating DPM Brickwork/Block work/steelworks and insulation Timber work Roof work (clay tiles or sate -chinese/spanish) Windows Weather tightening Heat Plumbing and in house drainage Electrics first fix MvHR Drywalling (metal furring channels and then either tape and joint using plasterboard or MGO) trying to skip the wet plastering but enhancing the sound insulation Stairs and balustrade Bathrooms Tiling and flooring Kitchen including separate scullery Internal doors and skirting (composite skirting boards) Decoration Second fix electrics Lighting Patio Landscaping Epc (Any thing I missed -please advise) I dont envisage I would be able to do all in one go so happy to divide the project in phases if required. Would really appreciate any help/feedback/insight that can be provided.

Hello, trying to figure out a possible wooden floor on foundation construction. Given limitations on allowed building height, I'm trying to win as much vertical space as possible. One thing that could help in this is lowering the ground floor as much as possible, and I have come up with the following draft, further detailing may be necessary, dimensions can change... My main concern are moist issues, arising from wooden beam floor starting at about ground level... Any opinions on this approach are greatly appreciated!

Good morning all, I have a few questions regarding a raft foundation. I am building a temporary structure in the fom of a mobile home whilst i get the main construction underway. The site is exposed and in the windiest area in Europe as such instad of piers i decided on a raft foundation. it is a 3.6m by 12 m raft andin my head a simple 100mm concrete slab would do. It will sit on glacial til so the need for hardcore may not be needed. So to my questions. 1) What alterations to the simple slab would you make? 2) the top soil has poor drainage, i was thinking of placing a simple draininage trench on two sides to drain away the water prior to laying the slab. If you have any links to documentation, videos or advice that would be great. Regards fiaraz

Hello. My wife and I are in the process of purchasing some land in Durham. As with most land up these parts, it's been mined, and there is a coal seam 11.5m down, 1m in depth. We have quotes to grout the land, one at 21k and one at 27k, however this is fixed price. Has anyone ever dealt with this before? And what foundations are suitable following this? Just a raft or trench? The bore hole report is attached if anyone reaaaalllly wants to help out ?. Thanks. Fern Meadows Bore Hole Report.pdf

Hello I am wanting to extend my kitchen (flat roof) by 2m but there is a soil pipe on the wall which needs to be demolished. The soil pipe is from the upstairs bathroom (house has a pitched roof upstairs like a loft conversion). Soil pipe runs up the wall and then goes up into the eaves and then 1m across before it connects to upstairs WC. I would prefer not to see the soil pipe on the new extension wall so two questions are : Soil Pipe and Sewer Questions (1) If the soil pipe is boxed into the kitchen (I am keeping a nearby wall that it could be run down) what issues will I have trying to get the soil pipe over or under the new foundations? (2) If boxing in is not an option, can I use two elbows to create a step down (if needed) to allow the soil pipe (with 1:40 fall) to run inside the flat roof? In relation to (2) I want to keep the extension as low as possible, so eaves height or ideally less (so flat roof starts at or under existing gutter). 2.65m high walls in house so eaves is reasonably high. Hence elbow step down question. Foundation Question The extension will only be two new walls. The length (7.5m overall) and the (2m) return. The other (2m) return is already on the house. The question is, the length will join to a wall on the garage. So 5m will be new and 2.5m will be existing end of the garage wall, will the garage wall (single brick) need to knocked down to put deeper foundations in? Or would the inner leaf of the new garage wall element just require the deeper foundations? Many thanks

I have been gathering prices from the usual suspects (Kore, isoquick, Izodom) for my insulated raft foundation. I thought i was up to speed however Kore has just thrown me off a little with the engineering costs sheet they supplied. (See attached) and below for the two specific paragraphs. So when we are talking Kore type - insulated foundations, when is a ground bearing insulated foundation, not a insulated raft? Insulated Foundation Engineering costs (One off).pdf

I need to finalise this for our timber frame company prior to them installing the raft foundation (they will also site the service ducts and drains). I understand that mains water needs to come in through a 110mm duct/drain pipe to allow space to insulate the main. I want water to go back out again to a garage and/or an accumulator that I can isolate from inside the house. Can both of these water runs fit in the one 110mm duct, or do they have to have one each? Is there a more intelligent way to do it? I understand that mains electricity can come in via a 50mm duct. Can it also go out through the same duct ( to the garage etc) or do they need separate ducts, one in, one out? What about BT, (we weren't going to bother but nothing else is available and the 5G option using Huawei equipment is starting to look dodgy). I presume that needs its own duct and can't share with the electricity? Finally, as a belt and braces option, I'd like to put a spare duct in for a (potential) future ASHP, or AirCon. Would that be 110mm as well? And how would I seal it in a way that I could reopening at some later stage?

Hi, first post on these forums. Our building project has got to the stage where foundation trenches have been poured and block & beams are supported on blockwork. Before we go on, the ground has proved very difficult - heavy clay on a sloping site and water frequently pools on top of the foundation and hence under the floor. Because of this we are going to lay 100mm perforated pipe all around the perimeter and discharge it into the rainwater drainage exit pipework (below foundation level). The question is what material to use for backfilling over the pipe. I know it will require something like gravel with a Geotex wrap to prevent sediment getting into the pipe but I don't like the idea of bringing any of the clay back in as it will shrink and settle like crazy. There are to be paths and patios to most walls so whatever backfill is used it has to be well compacted. Would 10mm gravel (around the pipe) topped with Type 1 be sensible or any better ideas? The depth required varies but there's a considerable volume to fill so cost is highly significant.

The slab team from MBC arrived on site this morning. It's like having the building version of whirling dervishes who've just dropped a few speedballs. My word, they make progress! The team is headed up by Harry and he has 3 others in his team, but this will fluctuate a little over the course of the job with Harry needing to have a look at another job for most of tomorrow then the younger lad taking some leave to go to a music festival. Tsk, the youth of today! He worked like a machine, though, apart from the bit where he nearly rolled over one of the piles as he was looking in awed astonishment as a rather attractive young lady farmer drove past on the nearby track in a JCB that was most definitely bigger than the roller machine he was on. I don't think it was the vehicle that caught his attention so much as the driver. Sniggers all round. I arrived just after 8 am this morning and the first lot of hardcore had already been delivered. In total, there were 4 loads of type 1, but I piggybacked onto this and ordered an additional load (paid for by me) which the team will then spread and roller for me in the area beyond the bucket in the above photo, which will create a nice level area for the crane when it arrives to bring in the timber frame. I've had really good luck with the weather so far and hope it continues, but if it rains between now the completion of the timber frame, the site will turn to mud PDQ and slow things down horribly. Once the hardcore was going down and getting compacted, the piles were cut off to the correct height, leaving the rebar in position, ready to be tied into the beams. I have no idea what you call the digger thingy that they are using to move the stone around the site, but it's an impressive beast. It looks a lot like the bottom of a tank with its caterpillar tracks and then something a bit more transformers-like with its swivelly cab and arm. Either way, it was mechanical poetry in motion when driven by someone who clearly knew what they were doing. The team will have been working till 7pm this evening, so they will have got all the hardcore down and compacted and were going to start on the sand, if they had the time. The first load of sand arrived about 4.30 this afternoon, more to follow on tomorrow morning. As well as working 12 hour days, Harry has already had a chat with the neighbours to let them know that they will be working over the weekend, too, on both days. The insulation is due for delivery tomorrow and they will be putting the pipes that carry the service cables into this, along with the UFH pipes. I'm not sure when the steels will arrive, but that must be also imminent as the piles will need to be tied in before the concrete is poured. The building inspector is coming on Monday to check out everything before the pour. For interested parties, THE CONCRETE POUR IS CURRENTLY SCHEDULED FOR TUESDAY. I've read a couple of horror stories and some not-quite-horror-but-not-very-nice-stories about uneven slabs, so I've told Harry that before they leave site, I need him to demonstrate with a laser that everywhere that a wall rests is absolutely level and within tolerance. Harry is a man of few words and he didn't quite bat an eyelid, but I explained that I would much rather that something like that is demonstrated rather than just verbally assured. He seemed fine with it. So, one final picture of the hardcore going down, from the garage side of the house. More blow-by-blow action to follow tomorrow.

Spent the weekend setting out our house. Hired a theodolite. Turns out theodolites have gone digital in the 23 years since we last used one ? but a You Tube video helped and we spent a joyous 3 hours setting out all the corners of the house. Amazingly, we have dug pretty much in the right place. And we feel more comfortable setting out accurately rather than measuring from a vague boundary hedge. MBC on site Wed / Thursday (in theory). Our sub-base is going in now (MBC doing the top 150mm MOT type 1). Just wondering about ducts. for water and BT. We also need to run the electric armoured cable in. We know we should have posted this question earlier. It has been bothering us for weeks. Site plan looks roughly like this. Its a weird shape (cut off a larger house behind). Plant room is shaded in yellow. Intended route of water (blue) and electricity (black, from kiosk) shown. Both go under the garage slab so we are ducting that tomorrow. Do we run these ducts at 700mm deep to the plant room and then up into the plant room? i.e. is the bit I am filling with around 300mm subbase as I type going to have to be dug out to put these ducts in? Or do they rise slowly and then go in the final layer (which MBC are laying)? BT duct is another question but please help us sort out water and elec first. Thanks.

As I'm getting the roof taken off the bungalow next week, I thought that I had best get my site insurance sorted out. When I was ringing around for quotes, every organisation asked whether the build would need piles in the foundations to which I answered in the negative as I had not heard anything to the contrary. HOWEVER, the lack of information in one area doesn't equate to certainty in another so I contacted MBC for some information from their SE as to whether he felt, at this stage, I would need to have piled foundations before going ahead and purchasing insurance. The SE, via MBC, got back very quickly indeed. This is the plan of our site with the existing and new structures superimposed, as well as where hedges and trees have been. The handwritten comments are self explanatory, but the orange areas are where the excavation needs to go much deeper than usual, probably about 1200mm, then back-filled with hardcore. Zarucki Fill_Excavation Depths.pdf So, to dig deep or to go for piles? The SE has said that both will work and the deciding factor is which is cheapest. In the sums I will need to do next week, I will also need to account for the cost of getting any piling system designed as MBC don't do this, then also getting the piles, foundation and super structure all connected up; please excuse the lack of technical terms. At the moment, I have no idea of what piling system would be needed, but if it's anything like @recoveringacademic experience, then it could be a process that requires a piling mat meaning I'll have almost formed the MBC foundation anyway. For those who want to read about Ian's experience, his excellent blog account of piles is here: Recovering academic's pile blog Of particular note is @Calvinmiddle's comment about his deeper foundation on clay for an MBC build. At the moment, I'm heavily leaning towards the deeper foundation and no piles. I will check out the economics of it; if it's a close thing, I would prefer to avoid piling just because I feel more comfortable with the principles involved in the deeper hard core layer and it avoids involving yet another contractor. But who knows - until 10.00am this morning, I had no idea what a piling mat was and a week is a long time in self-building.

Good Afternoon All. I seem to be progressing on my new build and I should have the Building Regs documents back from Potton in a few weeks. I am going to put them with my own drainage layout and Bingo ..the lorries can roll (or so i thought) After a talk this morning with Potton it seems that the bit in the Order that says THEY do all the layouts and stuff, is only applicable if you pay the extra for them to do the planning permission and all such like ...(sigh) I am OK with the drainage layout as its a "funny one"as we are going through our parents land to connect to all services .. ..about 50m in all (thankfully most of it in their garden, so we can do the work ourselves) What has reared its head is the "foundation plan" ...or "foundation engineer report" ...I had never heard the words until today from Potton. So I called up the company doing the foundations and they tell me they quoted (and expect it to be) they HAVE visited the site and we have got a soil report ....so.........100cm x 60cm / Beam and Block ...which from what I can see is a standard. They have told me they have never been ASKED to make an engineer report for a foundation Potton said they will give the foundation company the "Slab setting out plan" and "line and point loads plan" ? ....but I don't think that is the same So I guess what I am asking is... a) will the council expect this ? b) is it basically a drawing I could do? b) does anyone have something i could look at to get an idea thanks in advance Eddie

Hello Everyone, I am progressing with some quotes for the foundations for my Potton home. I must admit, the prices have me a little daunted as they seem to be a lot MORE than I was told about 6 months ago. I am not suggesting I am getting "shafted" but I want to run it past you guys to see what you think. I am building a Potton Timber Frame and have been advised that Block and Beam would be the way to go ....easier and more friendly on the surroundings (i.e better received by planners) The house area from looking at the architects footprint and adding on roughly 50cm around (I just did this to be on the safe side for my working out ...I am not sure if it actually done) ..I am coming up with an area of 121.81 Sq Metres with a Perimeter of 49.82 Sq Metres. Now I have the first quote and it is over £23k, I know this company is trusted and has done many foundations for timber frames...But does this seem expensive? I have snipped the basics from the quote below ..so you can see what it entails ...hopefully someone on here will know what some of the specifics mean thanks

Can anyone remind where I can find the post discussing how many ducts to put in before pouring slab as I cannot find it. I have so far: Main electrical incoming supply Telecoms (Phone and Tv for exterior aerial) Power to garage Power to gates and possible camera/intercom (in separate duct) Exterior lights (may come from detached garage but I realise better control from house) Water Duct from plant room to kitchen island electric and water (internal duct) ASHP (water and power) Spare All these will basically come up in the plant room and some may never be used but better to have them in when we pour the slab. Any others that people have put in or wished they have put in or can point out the thread I cannot find.TIA

Thanks to the members of buildhub for the constructive advice and a good ground worker we have managed to get our foundations in. The archeological watching brief wasn't the problem we had feared and nothing was found to delay this first step of our build.

I've realized we have the available height to add an additional sheet of insulation under our 100mm ground floor slab. Originally I had planned on using 2 x 100mm EPS70 with the DPM underneath as stated by Jabfloor. If I add an additional 100mm sheet on the bottom would there be any issues using it as a blind and sandwiching the DPM above it but below the upper two sheets? Consensus seems to be EPS can get wet - but Jabloor to state DPM first then EPS hence the doubt... Also any additional issues going thicker with EPS70 rather than one of the denser variants? thanks