Saul

Looks like I was wrong about there not be a professional on the planet that would assert that 1:10.5 could ever be used to build a house. They’ve found a mortar specialist Expert Witness that today said you could happily build a house with 1:12! He thinks that mortar test results are meaningless, that sandy mortar and erosion is normal for new build houses which use modern factory cement that contains special ingredients so erosion doesn’t mean it’s not strong enough on the inside. It’s no surprise that the builder is doubling down on their stance that they have used M4 regardless of the evidence. Lab results on my Inner Leaf and Above DPC have come back as 1:8. This is obviously going to end up in Court and be an Expert Witness v Expert Witness decider.

I discovered the issue with the mortar less than a week after moving in. It was therefore raised within the Defects Period which lasts for 2 years so Protek the Warranty Provider don't get involved. They cover the next 8 years. We are instructing a specialist Lawyer and commissioning Structural Surveys including extensive mortar tests above DPC and on the Inner Leaf. Bizarrely the Mortar Supplier has weighed in on this and said that they are happy with the Lab Test Results for the below DPC mortar which came back with ratios as low as 1:10.5. To suggest that such a mix could ever hope to achieve a compressive strength of 4N/mm2 is crazy and we are sure there is not a Structural Engineer on the Planet that would agree with that as an Expert Witness. I appreciate many Mortar suppliers do not adhere to NHBC Mix Ratios for Cement-Sand and instead use Design Mortars that aim to achieve compressive strengths set out in BS EN 998-2 but that surely means there is a range of mix within manufacturing tolerances that would never extend to the results we have back from the Lab so far. Regardless of ratio the lab state that on average over 90% of the material component of the sample was proved to be Sand leaving 10% for Cement, Lime, Blast Furnace Slag, Additives, Whatever. This is going to be a drawn out battle I am sure. Time for the professionals to take over!

Some samples taken to day from above DPC behind cladding and Inner Leaf by cutting through plaster board. Didn’t need power tools to remove as immediately disintegrated and as you can see looks like pure sand in the bags. Lab tests to follow. This will be put into the hands of professionals and lawyers to work on a proper resolution but looks like a pretty catastrophic problem for us homeowners, the developer and everyone else that lives here because you’d presume 42 houses being flattened would be a serious blight on the development. It seems crazy this could happen!

The Builder did their own tests and the result have come back even worse! The at best sample showed mortar with a cement-sand ratio of 1:8.5 but it went as weak as 1:10.5. The builder is claiming this mortar was delivered to site from Marshalls ready mixed. They admit they made a mistake and ordered M4 when they meant to order M6. Clearly M4 which is typically 1:4.5 to 1:6 cannot spontaneously transform to 1:10.5. They subsequently tested 42 other houses and all have the exact same issue. They have begun repointing and were meant to rake out 68mm on the beds and perps across panels no wider than 1.8m. The builder said for safety they were ignoring the Structural Engineer’s Spec and did 60mm on beds and 10mm or perps however they then went much wider than 1.8m so that contradicts their safety argument. The Structural Warranty Provider has since said because this is a material alteration that the Structural Warranty below DPC is now Void but the rest remains. It has also been pointed out that even after remedial work the house now fails to comply with BS EN 998-2 because it is not 100% M6 and the residual mortar that was left has no relative compressive strength. We are about to engage a further investigation into the mortar used above DPC and on the Inner Leaf as we have been told that this was also Marshalls M4 but clearly something has happened post delivery to adulterate the mix. This is hugely stressful and I imagine we’re looking at demolition if the results above DPC and on the Inner Leaf do indeed match those shocking results from below DPC.

I feel like the 1 part of the 1 to 6 was optimistic as it really does fall apart like a sand castle with very little agitation. A crack has appeared along the entire side elevation. I’m sure they’ll pass it off as just in the render and part of the process with a newly built property but I’m expecting to see more signs of instability given what the exterior wall is standing on. Photos of the block work internally show that the mortar is grey in colour so it’s just this DPC course of bricks that were laid a short time before the block work was done. Still waiting for the contractor to attend to inspect/carry out their own (“witnessed”) tests. Very stressful!

I thought building regs were 1:3. Their test will apparently be witnessed but I still need to ensure the sample taken is the one that makes it to the lab. But yes whatever the technical mix it clearly isn’t doing its job. The DPC was laid in April and I’ve been in 3 months. When it rains and bounces back up at the mortar it gets visibly wet and holds the moisture and then as it dries it sheds sand like in this photo. I sweep it away and then there’s more after the next rainfall. This gradual erosion is on top of the chunks falling out like in the vertical gap shown in original post. Hopefully they’ll agree to rake out and repoint. The DPC membrane is also recessed 25mm in several places. They scraped out some mortar for a small section and added a thin strip of membrane but watched them and it looked like a right bodge. The retaining wall behind the house was done with engineering bricks and grey mortar and is solid but that was a different contractor.

Posted about this before but now extremely concerned so would appreciate comments / advice. My house is built on a Piled Slab with Rendered Block Work. The Damp Proof course of S2F2 Bricks have been laid using 1:6 mortar as confirmed by Independent Professional UKAS certified Lab Report. To be honest you don’t need a lab report as the mortar is washing out every time it rains and if you tickle it with a screwdriver it falls apart like a sand castle on Margate Beach. The side elevations have stronger mortar in places so clearly different batches but the majority of the front and rear are extremely sandy. (Also a side note, not sure why the front protruding pillars are not sitting on the concrete base but appear to have some kind of pad stone below them. The house was signed off by building control and has a 8 year Protek warranty that kicks in after the builders 2 year warranty. They are being very slow to act and insist this is 1:3 mortar but it very clearly is not. I’ve been asked not to contact my house insurance, mortgage provider or warranty provider until they have conducted their own tests. I’m very worried the house has the structural integrity of a Kit Kat and that it will be condemned and need bulldozing and rebuilding. Cheers Saul

it wasn't my architect and didn't think you'd need one for a simple garage. Have now got a designer working on it which is costing £600 that I'd hoped not to spend.

I didn’t draw the upstands. They would border around the front and sides 150m above the top of the front ferring but the back will be open to the gutter. Proper drawings are being done. This is just me playing on Sketchup.

architect says that the eaves height of a flat roof is measured at top of roof, ignoring the parapet which would sit above the top of the roof from the Government Website http://data.parliament.uk/DepositedPapers/Files/DEP2012-1435/Parapets.pdf For the purpose of measuring height, the eaves of a house are the point where the lowest point of a roof slope, or a flat roof, meets the outside wall. The height of the eaves will be measured from the ground level at the base of the external wall of the extension to the point where the external wall would meet (if projected upwards) the upper surface of the roof slope. Parapet walls and overhanging parts of eaves should not be included in any calculation of eaves height.

architect says that the eaves height of a flat roof is measured at top of roof, ignoring the parapet which would sit above the top of the roof

Upstand requirements for flat roof design IKO TEAM 09/01/2022 A frequently posed question when designing flat roofs is “What upstand height do I need?” On the face of it a simple question with, one may think, a simple answer. Most of the time the simple answer is “150mm above the finished roof level”. We may give that advice but unless we probe further can we be sure that the advice is fully understood and correctly interpreted? In our experience, not always. BS 6229:2003 ‘Flat roofs with continuously supported coverings Code of Practice’ and BS 8217:2005‘Reinforced bitumen membranes for roofing Code of Practice’ both state that if unwanted water ingress into the building is to be avoided all weatherproofing upstands occurring around the roof area; (which would include abutments, rooflights and service vents etc) must have a minimum height of 150mm.

I forgot the 240mm I Joists from the list summary. The joists will run Side to Side so no need for a Steel. The door mounts to the face of the pillars inside. The Door is 2000mm tall but the running gear internally will be 140mm over the height of the door. Apparently the upstands don’t count as Roof Height so I should be able to do this in PD at 1m boundary.

Would love to get advice & thoughts on how a serious issue might be appropriately resolved. Lab tests have just confirmed that M4 mortar has been used below DPC on my house. Further to this it appears the DPC Membrane has been laid quite far back ie it is recessed from the face by about 25mm. This will presumably cause bridging, especially with the sandy M4 mortar and therefore result in rising damp. The DPC has been laid in rough face bricks rather than engineered bricks but they are classed as S2 F2. Feeling anxious and worried. The house is rendered Block above DPC. Thank you

Looking for any final advice before I move forward! Thank you! I’ve now moved in and need to get this garage built asap. It’s looking like it’s going to cost £35k all in which is still a massive amount of money. My issue is now with the internal ceiling height I’m like to get being 6’2” tall and thinking internally it’s going to be under 7’ To get this garage built within permitted development I will be GIA under 30m2. Garage Width will be 5.5m and Length 5.8m Externally. Block Built with Piers and Rendered to match the house. Maximum height under PD is 2.5m. The Double door will be 4500mm wide by 2000mm tall so I only have 500mm left!! The Headroom needed for the Door is 140mm. For the flat roof I need at least 240mm tall I Joists for the width span plus I need Ferrings and then a Stand Up 2500mm Max Height 2000mm Door Height 140mm Door Mechanism Head Room 78mm Ferrings Height 150mm Stand Up I’m over already by 88mm This is crazy!

Will do though not sure I can manage the weight of 5.83m long standard wood joists. I'll most likely go standard I Joist and Ferrings. Not seen anyone sitting I Joists on top of the block work or if they have how these would be secured to the blockwork...perhaps upside hangers. The house has Web Joists sitting on hangers within the walls but don't want to do this for the garage as would need another row of blocks and not keen on that design for something that doesn't have a floor above it.

Presumably you would add one firring per joist. Just found a site where they are £3.25 per m up to 6m. For my build with 5.83m this would mean 15 x 5.83 x 3.25 = £285. 2 rows of bricks on one side of garage would be around £50 excluding laying labour. I don't like the idea of offset walls but don't know why that wouldn't work unless there is a stress issue on the I Joists from not being square if they were ever subject to heavy load from snow etc. At the same time at the high end of the firring ie 150mm above Joist I'd prefer to know that the OSB was attached to the joist where in reality it will be nailed to the Firring which will be nailed to the Joist. The wall ties won't offer any protection against wind strain. Who would have imagined that 3 walls, a floor, a roof and a door could be so involved!

Thanks. I've pretty much abandoned the idea of a gutter at the back of the garage. As clean as that would be I'm not putting a steel across a door gap that wide as it will be super expensive. The issue with a 5.83m Firring is that it would be approx 150mm down to Zero. I just feel that those would be impossible to cut consistently.

I have read all the previous chains on flat roofs and know pitch angle and methods has been covered to some extent already but trying to wrap my head around why you would use Firrings as shown in the first picture when you could just create I Joists that have a slope manufactured within them ie by cutting the OSB Web such the bottom edge is flat and the top edge is sloped. In effect the I Joist would then have one end being 450mm tall and the other 300mm tall overall. (I know in the below example I have run Firrings front to back. If I used them this is what I would do as would rather have the gutter at the back) As well as custom angled I Joists I know I could also build up one side wall to be taller by adding a row of 2 bricks which would achieve the same fall off with guttering placed on the side of the garage rather than the back. I just don't like the gaps that this creates and think an angled I Joist allows everything to be nailed together square. As this is a single skin 100mm Block 7.3 build with Piers and no heating it won't be insulated and will simply have an 18mm OSB roof with EPDM Rubber, Fascias and Guttering. STS board will be attached the timber work and the sides will be rendered. Roller/Double Door. Appreciate any comments. Ultimately I need to build this as cheaply as possible as people seem to think £45k for a double garage is normal. I want to achieve this for max £20k in total including base finished and ready to store my classic car. Cheers Saul

So looking like this will now be a Block Build Garage Rendered in Weberpral Monocouche to match the house. If anyone knows of a good building company that might want to take this on in the Bicester/Oxfordshire area any recommendations would be appreciated. Plot shown as per attached.

£28-45k. Happy to do quite a bit myself internally and have an electrician father but definitely want the water tight structure handled by pros. Best of luck finishing yours. looks like great fun!

I am aware of them but put off by negative reviews and wondered about it's strength as they look more like posh sheds. Over a Double width door I'd be a little bit scared but am sure yours is fine especially with the shelter from the wall next to it. Good luck with the door!

Up to £45k = insane in my mind. Yours looks cool. Mine is on a housing estate so have to be mindful of the neighbours. Keeping it basic size for 6x5.5m Double with flat roof.

I intend to build a fairly simple double garage to house a classic car in the New Year. I'm astonished by the quotes that are coming through and wondered if anyone had experience with kit builds or whether getting a Block garage built and insulating it myself is a better more affordable route these days. I know Timber and other materials went crazy during the Pandemic but have prices not returned to normal? Thank you

Velfac yes. Not the grinder slip. Just the way they are sealed. I would expect it to be flush to window frame or look tidier. They're secure but look like they're just floating and not connected to brickwork. It's more about bad aesthetics and looking unfinished.