Gus Potter

Don't touch the flanges of the posi joists.. it's dangerous, a big safety risk and you could really trash your house..

What an interesting project. 1890's.. maybe corbelled brick foundations or stone laid flat both on compacted earth. I seems reasonable to conclude that when the flags were laid (6ft clearance) the ground must have been fairly dry. For me the next stage would be to investigate outside, where you can, to see what might have changed over the years. If possible I would excavate modest holes outside down to the level of the bottom of the founds and see where the water levels are, while also gathering info on the founds themselves as you'll need this later. In some ways you need to think laterally / holistically. For example: 1/ Have the neighbours / previous owners built something that has changed the water levels and how the water flows in the ground. 2/ Do you have leaky soil / rainwater drains. 3/ Have you found old clay tile drains in the garden? .. these can be small sometimes about 3 inches in diameter with a flat bit on the bottom. They get blocked over time and stop working and can cause the ground water to rise. 4/ Is there / could the be a leaky mains water supply pipe that no one knows about. You can test the water to see if it is treated (potable water) if it is then you need to find the source. You can also install a rough ground water monitoring system yourself using some perforated pipe with a bit of gravel round it. This means you can fill the holes back in and dip them every couple of weeks. You'll need a datum.. but you can use a water level or a laser level for this.. plenty on BH. It may yield some clues as to the direction of flow of the ground water. Once you have this information you'll be better able to select the right option for the basement, maybe save yourself a lot of money?

That is some photo. Just wondering how the the screed / concrete is supported through the opening in the left photo.. it's got a bit of work to do to get past the pipe insulation..and what is that small portion of stud wall sitting on in the left photo? Like the curved walls. Right hand photo looks impressive with neatly clipped pipes.

@eandg try and get your hands on a copy of BRE disgest 365 Soakaway design..wait here on BH! It's an 8 page document with some worked examples. Also it's simple enough to help you get a handle on the basics. Once you grasp this it will help you form a view as to what will and won't suit your site. If you get the bug you can automate it with excel.. and play! Now you may have a discharge constraint. You have probably come across flow control valves, say the Vortex / Hydro brake type and had a glance at the cost. With a bit of careful design you can do this on a small scale using a plate with a hole drilled in it.. an orifice plate.. and you find example orifice calcs to work out the flow. What you do need to do it to add some other bits.. a good filter to stop the small hole getting blocked and an over spill. I did a job a while ago using this on a small industrial unit using an oriface plate and a well designed grill filter, silt trap. So long as you can justify the flows and design it so it can be maintained the authority seemed happy, so was I with my effort. Did the hole thing for less than £ 150 quid from memory.

In these old timbers I would avoid nails too if possible. The timber will be well seasoned, quite hard possibly and already have a few splits etc in it. The spiked (toothed) washers work well in new timber as it still quite soft, even some of the knots. But with old timber you really need to crank up the bolts to make the washer teeth bed in and form a close joint. You can easily do more harm than good to the old wood, it can split inder the bolt tension load and cause a headache. I would look to see if you can use M12 bolts in cleanly drilled holes. As a ball park you want to look at putting 2 number bolts per joint with 50 x 50 x 3.0mm thick square washers under the head an nut. The trick here is to see if you can get the bolts in while maintaining the edge and end distances. See table below for a guide. End distance is the distance from the bolt centreline to the cut end of the timber. Edge distance is the distance from the bolt centreline to the edge of the timber. Unloaded means that the force in the bolt is acting away from the end or edge. Loaded means the bolt force is acting towards the edge or end. With a typical roof connection the timbers are at an angle so we are left with having to use the loaded values. Sometimes this does not work so you look at M10 bolts.. then one larger bolt.. the joys! Mull this over and have a word with your SE.

Yes would be up for that and chip in with content. There are some great blogs on BH. The trick would maybe be to identify what is current on BH while also covering say basic beam design, how structures stay up and the things to consider if you are say self building or extending. I don't know how hard it would be for the mods to create some kind of indexing system to make it easier for folk to find what they want within the blog? This probably already exists? You could take @Grian Something like this although small and a bit different it has a lot of different structural elements that could be used as great examples. It's not just the structure, it's how it interacts with the insulation, wind.. and so on.

Oh yes.

Looks like the main house may be a lowish pitch roof.. guessed here as can see the house behind. @BobAJob How do you find a structural engineer? Try the internet and look for local SE's.. you may find a few small outfits, one man bands that keep below the vat threshold so you avoid the 20% uplift on the fee. Also ask friends who have had an extension built say, they may have used an SE. Do I need a surveyor to examine it and advise? Lots of £££ try the Se route first as they often have a list of reliable builder contacts. I think I might get the whole thing ripped off and start again. I think it might cost around £12k to get it done right. I don't mind paying. It's finding a decent tradesman round me is almost impossible. They all just want to get the job done quickly not correctly and onto the next job. Then you end up paying multiple times when you could have just paid once to get it done right. It's a disgrace. If you can post some photos of the roof so folk can see the shape, photos of the outside walls so you can see how it drains at the moment. If you have 12k then you could explore options.. could be upgrading of the walls too or maybe.. just a lantern? pushing it though but.. who knows.

In the spirit of BH... you may need to offer up a bit more than an apology! maybe an "abject apology".. or a bottle of something in the post!

Hiya @LaCurandera "Kitchen in the "new" 60s extension - good idea which I'll explore. There are services over that side (currently there's a bathroom roughly where the snug is) although boiler isn't. One consideration is that we are unlikely to go back further in that corner (where office is) as that's right on the boundary already and possibly much extra would be within 45' of a rear window of next door. Hence stepping in the extension. So we'd be taking out that left side wall where the stairs might go up which is internal now, but originally external. I'd tried to work with as many currently walls downstairs being unmodified (or at most doors filled in etc). Maybe being a bit braver would be good, although presumably costly. " Don't get too hung up on the services for now, keep an eye on the where the electricity comes in though as shifting this can be an issue. Good point about the boundary issues, daylight and over shaddowing. You also have fire protection.. fire boundary conditions. I would get an SE on board that your Archtectural designer has a relationship with. The SE will just keep a watching brief and give the Architect pointers as to where a small layout can be changed if need be that will save a fortune / bring the job within you budget. Remember that this design is going to be an iterative process. To avoid wasted time and expense get the design team you need together early and let them bed in.. and get to know what you really want out of this house as you live in it over the coming years.

As always Steamy you are spot on! and elegant points made. For all, hope this helps the keen tecky. Take a timber floor joist, or a ruler at home. Support it at each end an apply a load in the middle. The ruler bends down so the top shortens and is in compression, the bottom stretches so is in tension. Masonry ( brick walls) are not good at resisting tension.. so if you add enough load to the top of the wall then the masonry never gets to the tension stage. Steamy is spot on.. this is the one of the basic basic concepts of prestressed concrete design. Steamy mentions what is called "buckling".. again correct. Put the ruler on it end and push down from the top. Suddenly it will give way.. this is a buckiling phenomena.. Euler circa 1700's the mathematiccian developed the theory behind this and is a fundamental principle underpinning what SE's do today. So yes Steamy, if you add to much load you risk buckling.

Grian.. remember if you make something like this fly, enjoy building it and make some money then you got a leg up from BH.. so a small donation to BH would oil the works! I do think that if you have a local joiner on hand you could build a safe structure for holiday accomodation out of timber frame for not a massive outlay. You could almost have detachable cladding.. in effect the structural TF sits there and the outside cladding acts as a rain screen.. could be just recycled pallet wood at the very basic. As this is a temporary moveable structure not a house that you get a mortgage on that has a life expenctancy of 60 years you can afford to change the cladding and appearance if you wanted to suit you target market. I don't know where you are but the saw mills do some real rough but cheep timber off the outside of the log that can be used for cheep rain screening. You could use all sorts of material depending on what visual impression you want to give out.. I love this stuff. You could have great fun exploring what you can do and how you tailor the appearance to your intended holidaymaker market. My sister has a B & B on Tiree so the market there is split between commercial clients coming to serve the radio mast, fix the fridges in the coop ect and at the other end folk going for a holiday that want to stay in a nice place. Keep posting!

Thanks @SteamyTea Much appreciated. Inverted roofs are something not much touched on on BH. More commonly you see them on larger refurbishment development and commercial stuff. They do have their issues but this for something like what @Grian wants to do on a limited budget while mitigating the financial risk, the constraints i.e moveable.. it could be an elegant, cost effective and environmentally positive solution. On the technical side I mentioned TF. You can increase the stiffness of a TF panel (thus better able to resist the sideways wind loading) by adding compression from above so the slabs perform this function.. it's all about getting the different elements of these small light weight buildings to do more than one job.. you look to get your pound of flesh out of them. Yes in a windy spot you will probably still need to tie down with cables for a bit of robustnees but the in the round I think this is worth a look at concept wise.

@LaCurandera Well done, colour coding can be really helpful. Persevre with the gridlines if you can, it will pay divdends later when you get further down the road when you get your Architect on board etc. Also, well done for making a start on the layout.. if it's not your day job it's a often ahard .. and even if it is your day job.. it can be challenging (but enjoyable) to come up with a good concept. On the layout my first impression is that I would want to explore shifting the utility, and GF bathroom to where the snug is.. that is the "working part of the house". I like your idea where you come in the front door and you get a line of sight right through into the back garden. Much will depend on the aspect of the house and where the sun rises and sets etc. To get the best out of Bh also mark how your plans sit relative to North.. there are some real innovative folk on BH. I see you have a big landing up stairs, but a modest stair case. When you come in the front door you almost enter a corridor.. I would look / explore to make the rooms upstairs bigger, reduce the upper landing size and spend the money creating more of a wow factor as you come in the front door. On practical point .. sounds great having a bathroom close to the main entrance.. but..! If you like the idea of a "grand entrance, upper landing then you can sometimes achieve the same effect but the use of a roof lantern and some well placed mirrors to create the same effect while increasing the usable space in the rooms. All the best and keep posting.

I would go ahead and get the MVHR up and running. If you compare the cost of your flooring cf regular replacement filters then.. if the flooring goes wonky then.. big disappointment. It's also all the other finishes such as doors, facings, say you kitchen cabinets etc.. start "breaking" them in now and if issues arise it's easier to address now than later?

Hiya @LaCurandera Interesting project. To get some structural feed back it can help a lot if you put some gridlines on the drawings. Put a grid over the new layout and transfer onto the old. Now you can easily see where the old walls and founds below relate to the new. Sometimes when you want to put an extra storey on you find the old founds can't quite take the increased load. Before you throw in the towel you look to see if it's possible to spread the load out a bit and make the internal walls carry a bit more. Also, if you can put a grid on it make it easier to refer to when making comment on the Architectural design.

Hello Grian. You could have great fun with this. I've been lucky enough to have dabled in this on the structures side on and off over the years; light weight cold formed steel / TFstructures, high end man caves etc, it's enjoyable. In terms of proving it is "movable" then if you made the main section no wider than 2.9m then this would fit on the back of a low loader without being classed as an abnormal load as I understand? I wonder if you could also build it with extra modules, like those mobile homes that once parked the sides extend out. This would allow you to detach the side modules. Yes, you would need more trips to shift it you started with two modules that are a similar size to a 40 container you could then add bits to provide an improved layout, less corridor and more living space? In terms of how you build something like this.. it looks like you are near a sea loch. I would explore doing it as a TF. You could do it as metal stud ..dry wall idea or thicker cold formed steel sections both with limited life expectancy but TF is more suited to a local builder, (or say a joiner) and more survivable in a marine type environment as it does not corrode. Also, easier to insulate. You could almost panelise it so rather than transporting the modules you diassemble and transport it flat pack style, like a fully serviced module construction. Ideally you want to see if you can keep some residual value in it in case you later want to flog it (to say a self builder here as temporary accommodation! and do something else.. at least any residual value should cover the cost of getting rid of it or upgrading? I'm not a guru on the caravan regs but as I understand it so long as the structure is capable of being moved from one place to another then you are on the right lines. I don't think it's a massive engineering challenge to do TF modules that you shove lifting beams under and crane onto a low loader. If flat pack then four folk can man handle them on and stack. In terms of structural wind loading with a bit of thought you can design and build a strong TF easily capable of standing up in the wind. The big thing is you need it to be light weight so you can man handle it.. but then it wants to fly away in the wind! Also for simplicity and to keep the cost down you probably want to put a flat roof on it.. which is hard to insulate and ventilate. But.. the roof can be an inverted warm roof. Here you have a roof as follows;.. could be exposed timber on the underside (saves the cost of the ceiling) , then say 18mm marine ply, the water proof layer (say EPDM single ply membrane a pondliner almost), then the insulation and say paving slabs on top. The paving slabs act as the sound proofing so folk don't get woken up with the hail, the rain and birds tramping about on the roof at 5.00 am in the summer. The slabs also help act as ballast to stop the whole thing lifting in the wind and the insulation flying away. When you want to move it you take off the slabs, recycle.. either flog the insulation or recycle.

If it was my wall.. which of course it's not I would hack off the render and give the stone a wire brush. Then leave it for a year. Provided it's not holding back something that could, if it moves, pose a safety risk or fall on someone. During that time see where water seeps out, if it does. When you have time, investigate behind the wall to see if there is some drainage too. Then once you have worked out what is going on behind the wall you can then decide whether to point or render and where you maybe need to install weep holes. The render at the moment is probably doing more harm than good. Re rendering with mesh or not, lime based mix or cement.. is just kicking the can down the road.. and could be a waste of time and money. Take the render off and let the wall breath and relax!

Good stuff. Sit down with your SE and look at your options now you are starting to get a feel for the cost. From time to time having to value Engineer can throw up other design options you may have not considered before. You may get a pleasant surpirse and save some money along the way. If you want post some cross sections so we can see the shape of the roof etc. Good luck.

Plus One

Yes I read it that way, the intent is to decouple to protect the ceiling. The term sistering can be interpreted in different ways... then the different types of connections take on a life of their own! All good fun though. Converting lofts can be quite a challenge! .. but satisfying. Simplysimon has great point. This can be done provided you have the height to play with in the loft. It can work structurally but here is the rub. While you can as a designer can prove it all works and produce a specification, in real life unless you know the Client is going to need to have you supervise the work on a daily basis as the chances of a builder doing it properly are low.. and that is a safety risk. Thus I often avoid this elegant and economic approach for safety reasons on domestic projects. I do have a pal that wants to convert his attic and this is something we will look at as I know he will be absolutely dilligent and do it correctly. The secret and elegance in Simplysimon's potential solution lies in the concept that the screws only provide the compression of the longitudinal joint while the glue cures. After that the screws become essentailly redundant. For the glue to work the faces of the timber need to be a little rough, flat for a good mating surface and absolutely clean. The glue needs to be a structural glue such as Cascamite two part resin. What we do (and now have) is to create a 2 ply glulam beam and use the same analysis techniques.

Jenki Lot's to look forward to. Looks like you are pretty close to the sea so check the plastisol specification regarding corrosion near the sea and where you stand on that re cladding warranty on the pods. All the best.

And really difficult to get off tools and all the other unwanted places it seems to get! Good idea by the way for Onoffs flints.

Let us know if you try the SBR. Worth a shot I say.

I suppose it's a question of terminology. Some folk think that sistering means doubling up the joists and connecting the two together along their length so you create a joist twice the thickness of the original one out of two bits of timber coupled (bolted say) together (the old and the new).. thus roughly you can double the load without a bad outcome. But remember that the old timber will have creeped a bit and seasoned so will probably pick up a bit more load first before the new "bendy" timber starts to pull it's weight. Something to consider if you have a period ceiling below. Or sistering can maybe interpreted as adding another joist in between the existing? making it a bit higher and thus you create a floating floor..have done this where you really decouple the new floor / attic loads from a ceiling that is sensitive, say an ornate ceiling. There is quite a lot to think about when doing loft conversions. Often you don't want to mess with the floor / ceiling below as you are living there. Now a plasterboard ceiling often has dwangs / noggins so to sister (doubling up) you need to cut them, to get your new timbers in at the same depth as the existing joists.. and refix the dwangs / noggins. A bit of a guddle (faffing about) = £cost. Often you find that there are cables, a few pipes etc and to keep the cost down it's helpful not to have to move them, especially over the consumer board area if a lot of cables run up into the loft. A lathe and plaster ceiling relies a lot on the plaster squeezing up between the lathes and expanding (belling out) to create a mechanical key. Call these the snotters. Would be interested to hear what the local term is in different parts of the UK. If you knock them off then the plaster will become loose , particularly as the timber lathes will have shrunk over time. Often it's best to have a look at what you have early on; can you move out, do you have period features etc and then see how you do it structurally to accommodate the constriants.