Gus Potter

@kelvin is correct. The construction courts / courts recognise that some Clients are experienced, some are domestic (inexperienced) and thus are afforded more protection under the law. Often domestic Clients get into dispute with dodgy builders who have written their own contract. While it can be difficult to argue against the terms of payment it is much easier to hit these builders in their weak spot which can be poor quality work that compromises structural safety. That could be anything from cavity width to incorrect insulation that could cause condensation that could compromise a structural frame. There are lots of ways to tie back bad work to safety considerations.. it's often knowing how you do that and present an argued and reasoned case. I do this with say the NHBC and other warranty providers etc who can be a bit.. (insert your own words) at times to speak. You can often debate to the ends of the earth about the quality of the finish.. but hit them on a structural issues and you often have the upper hand.. you make them rack up defense / consultancy costs and force them to employ their own Consultants.. who often won't touch them with a barge pole.

That is great advice. It also takes the personal element out of things. If you get the support of a good QS it will be good for your mental health not least and you may salvage a friendship.

From what you posted that looks like an expensive mess by the SE. These pads and the disruption look like they will cost you a fortune. It also looks unbuildable at a sensible cost. It's not just the structure it's moving electrics / plumbing, cutting floor joists and making good.. the absolute mess it will make during the works that needs to be reinstated at a cost. From time to time I see stuff by other SE's where I think.. fair enough.. but this is ringing alarm bells. The other big one is the sideways stability of the building and the knock on costs. Can you post a full set of plans. By that I mean the whole lot.. all floors and sections etc. If I'm jumping to conclusions and wrong on this I'll say so and take the flack.

Lots of agreable points here @OwenF To paint a bit of a picture I think Alan has in mind a single storey relatively light weight timber framed structure going on top of a basement, say a formation depth of 4.0m, insulation on that with a concrete box on top. This is a bit different from a heavily loaded raft (basement slab) say where you may want to recognise that the pressure bulb under a raft can be quite extensive and extend to a considerable depth, just say 2 times the maximum slab dimension.. Atkinson et al? Being pragmatic you could take the view that what you are digging out to form the basement is heavier than what you are putting back, thus the stress at formation level is similar or less. Now let's also say that the local geology and superficial deposits are pretty well understood. But due to the natural variation in soils you could end up being unlucky and build on the only rubbish bit. Now if that was to be the case then you could maybe even pick this up during a walk over survey.. notice a depression in the ground say as the soil has been loaded more histrocally than what you are intending to put back. If your formation is a 4.0m then investigating to 6.0m should cover most risks given the loads at formation level in this case. I often lean towards trial pits as you can really get down and dirty with the soil, also you expose a larger surface area of soil that you can "feel", look at, smell (if confident ground is not contaminated) and get a better idea of the strata etc. Also great point for @saveasteading on another post.. you can do some soakaway tests etc at the same time. Jury is out on this one, can only suggest this may be a requirement of a specialist basement designer, best thing to do is ask what they are going to do with the results. They may have a perfectly and sensible reason for doing so on this kind of design. On something like this I would want to try and understand as much as I can about what is lying say up to 2.0m below the formation as a perched water table / local artisian pressure is always a risk. For self builds the cost can run away if you need to indulge in extensive bracing of the excavation and have to manage ground water. If in good ground you could assess the stand up time, and try to mitigate the temporary works cost. With a fair wind you could just batter back the excavation.. simple if you have the space to do so. A contractor pricing this is often going to assume the worst and price accordingly as it is a one off self build. Their mind set is often.. it is a one off so if I lose a bit I'll not get the chance to get it back on the next job. If you plan out the works, sequence and provide the Contractor with good information it should help drive the cost down. There is a risk (will be in the contract) in that if it all goes south you'll have to pay more. But you may not end paying any more at the end if it does go south than if you accept a price from a contractor initially based on the worst case. Also if you have good ground information you'll be in a better postion to push back against a Contractor if they hit for unjustified extras.. you can say.. I gave you the info.. it's your fault for not reading it. I bet you've told so many people so many times.. set aside a meaningful percentage of your budget, give me the resources to do my job properly and I'll probably, nine times out of ten, easily cover my fee and could save you thousands or more.. If you look at the figure mentioned above we are talking a couple of thousand each way.. but imagine what it could cost if you encounter something in the ground that you could have discovered for that small extra amount of 1 - 2 thousand. That difference could get swallowed in a day or two on site with especially if you need a sudden re design.

Sometimes there is an easy way around this. Below is a screen shot of part of one of my designs where I'm strengthening a floor. The additional joists are shown in green hatch. You'll notice that at the top of the drawing that the sistering joists don't extend to the wall head. The roof on this job is a pole plate roof so there were issues around extending the joist to the wall head that I needed to avoid. The sistered joists are well fixed to the existing. The objective is: 1/ The big bending forces near the middle of the joists are resisted by the double timbers, old and new. 2/ A lot of the deflection is reduced by the doubled timbers where the bending stresses (near the middle of the span) are high. To prove this works you: A/ Check the double timbers for strength so they don't snap near the middle of the span. B/ That the deflection is ok.. how much they bend down by in the middle. C/ That where you only have the existing single part of the joist bearing onto the wall that is can take the extra shear loads arising form the extra load you are adding to the floor. D/ That the bearing strength of the existing timber on the wall plate is ok in terms of transferring the extra load to the wall head. E/ That any door / window lintels etc under the wall plate / wall under the joist ends can take the extra loading. You may find this approach works so long as you are not adding too much extra load to the floor... say by using a concrete screed for the UF.. a lightweight overlay UF should be possible. I would ask an SE say to have a proper look at this as they could easily save you more money and hassle than the amount you need to pay them. Given the size of joists you have (40x210mm) you may find the above works. You may need some extra noggings (dwangs) to stop the joists twisting at the ends. The above is one solution but you can often tweek it to avoid having to but a ledger piece to the wall or form extra pockes in the masonry.

Good question. Hope some of it helps someone, especially those designing their own TF in principle and some of the things you need to think about..I make some general comments. The two diagrams you posted look as they do.. but odd in some ways. Starting from the top. 1/ The grade of Glulam 28c.. your TF supplier? They I assume will have priced for this on how they operate / cost / lead times but a 28c often carries a significant price premium in one way or another compared with a 24c or a 24h grade which is less strong but is made from more readily available timber. I would ask the question.. is it cheaper to use a 3 ply in 24c or 24h and can it be fitted in? Ok.. you may ask what is the difference between the suffix c & h? A Gluam beam is built up from layers of timber glued together. When a Glulam beam is subject to bending forces only (usually from a floor) and rests directly on say on a wall head we can make the beam out of stronger timber on the top and bottom and put weaker timber in the middle. This means we combine different strengths (grades) of timber hence the c = combined so more economic. The h grade means that we use the same strength (grade) of timber for all the beam laminations so it is homogeneous = h Now in some cases, say for a beam resting on a wall this is ok.. but it is often NOT ok when we want to connect a glulam to something else using say Simpson Strong_Tie connections or a steel beam unless you design on the weakest bit of wood! and if you do that then why pay for a higher grade of beam when you could make it thicker say. Big heads up.. if you have a separate SE make sure they know what the TF designer is assuming! Nail spacing horizontally (600mm) . This looks a bit far apart to my eye. I would go for 250 - 300mm centres. Now this may seem a bit trivial to the naked eye but it matters when you do your design checks. A closer nail spacing means that you can treat the two Glulams as acting together (compositely) so you get more bang for your buck in terms of performance. The spacing shown looks odd. Ask the question.. basically has the detailer not implemented the SE's design? The nails are all shown with the heads on the same side. This is not good practice. Also the nail length is indicated as 75mm. 75mm less 45 mm only gives you a point penetration into the Glulam behind of 30mm which goes against the principle of nail design. I would specify a 90mm long ring shank nail for this. Ask why they are all from the same side, not opposing and appear to short. The distance of the nail down and up from the top and bottom of the Glulam. If we are using solid timbers nailed together then we often stagger the nails above and below the horizontal centreline of the beam by about 25-35% of the depth of the beam, it varies depending on beam depth so this figure is representative. We do this as solid timbers tend to "cup"over time. In other words the middle bows in or out from the centreline. You can often see this in old solid timber joists where the sides are bowing.. cupping. Cupping happens when the older wood shrinks differently from the younger wood. Now Glulam beams are not supposed to be too succeptible to this type of cupping behaviour when surrounded by air of the same moisture content on both sides. But if not they will cup to some extent. If you nail the beams together in the way shown you could cause them to cup and split the lamination.. now you have a problem! Suggest you go back and ask the TF designer if they have thought about this and can confirm that for your application all is ok given the 30mm nail point penetration which raises an eyebrow. Last but not least.. you are going to be fixing a ceiling and floor to the top and bottom of the Glulams possibly. The floor in particular serves to brace the tops of the joists to stop them twisting sideways and if you stop this you get a good stiff floor. Now the flooring nails will likely compromise the nails you show in terms of code compliance. That is why I sugest earlier that the nails are staggered above and below the horizontal centreline, it keeps them away from the flooring / noggings / ceiling nails. Suggest you go back to TF detailer and query. Check the specification and point penetration required by the flooring manufacture and you may find the TF and flooring spec clash. For all. At the end of the day once you get your head round the principles of how timber works then it's a great material to build a house from. The above is a bit tecky but if you think about it much is common sense!

Your Rockwool is probably a good balance. The important thing is to install it properly, no gaps and not pack the wall tighty.. it needs a residual air gap.... see installation instructions. Following the installation intructions is probably the most eco freindly appoach.

Not a lot, probably less than the door / window handles and the letter box on the front door. Forget it and move on.

If your half landing at the bottom is buttressing the upper set of treads / stringers against horizontal movement then you actually can show you need minimal fixings at the top. Think about a ladder against a wall with someone holding the bottom still. The load at the top of the stringer is horizontal only (as the top of the ladder can slip down the wall) which in your case is pushing against something solid. If you are confident your half landing can resist the horizontal loads then your problem is solved! All you need is a few fixings at the top of the stringer to stop the stair moving left or right in the plane of the top landing. Does this work?

Hiya. Well done you! it seems you are now getting into making big design decisions on the structure and how that interacts with all the other elements of the design. That all sounds great on paper but in practice unlikely to work given the nature of self building. It's your first self build so you have a huge amount to learn. I joists are good for carrying bending loads, say a floor. They are generally less appropriate for compression loads, say where you have openings with point loads from above. My advice is to avoid as the detailing and connection design will be horrendous / costly and unlikely to be "self" buildable. Take the hit on thermal bridging and consider standard solid studs or something like a space frame. @Kelvin has done a cracking job using a space frame and has lots of practical knowledge on how you make it work and the pitfalls.. to avoid.

Ah now I see! Have to say.. you're quick with the representations and thinking on your feet.. do you want a job? The more screws / nails you put into the head of the stringer the more likely it is to split... leave it alone. We have all sorts of rules for timber fixings, edge and end distances, the load direction and how the load is orientated to the direction of the grain. What you propose is messy. Can you.. Using a structural glue and screws (provides clamping for the glue and a bit of redindancy in case the glue is duff) to thicken the stringers on the inside with MARINE PLY not OSB. The grain of the outer ply should run horizontally. Say stringer is 33mm thick + 18 marine ply = 51mm. Make the ply cover a good area of the stringer, may past the next tread down. Bolt a 70 x 50 x 6.0 thk steel angle to the vertical leg of the angle that sits inside the bottom flange of the UB. Suggest 2 no M10 8.8 bolts though the short leg into the angle section you show. The 75mm leg runs parallel to the stringer. Drill the 75mm leg of the angle and fix that through the ply and into the stringer using short M8 x 40 long coach hex head screws. My first guess is that you need 4 coach screws per angle as the stringer length is pretty short I seem to remember from your previous posts. The long leg keeps the fixings away from the end of the stringer. The ply prevents spliting of the stringer end. Below is a screenshot of the edge and end distances you need to comply with based on BS 5268 part 2 2002. Note the load direction.. you have clocked that earlier when you recognised that some of the fixings may not be doing much. If in doubt always assume the worst load direction. d = the diameter of the bolt. Some bits from the table are key.. edge distance.. the top coach bolt needs an edge distance of 4d so it doesn't split the top of the stringer off. The bottom fixing is pushing into the grain (meat of the stringer) so only needs 1.5d. You want to keep the coach screws 7d from the end of the stringer (as the grain is at an angle to the load direction) to be conservative. 7 * 8.0 mm dia = 56mm. For steel with a drilled hole the edge distance is 1.4d = 1.4 * 8 = 11.2 mm... say 12.0mm 12mm + 56 = 68 < the 75mm leg of the angle.. and there you have a compliant connection even once you take into account fabrication tolerances. If push comes to shove we can use more detailed calcs to refine the connection design.. keep it simple and avoid. I mentioned 4 screws. They need to be 4d apart vertically = 4*8 = 32 mm. If you draw that out you may have room for more fixings in the vertical plane if need be so. For all. The above table is a handy reference if your learning about TF construction.

Hiya.. The glue thing is ringing alarm bells here! I'm not saying it can't be done.. just before you do something like this you need to really understand how the materials are behaving. Also imagine you came back to me and said.. Gus can you prove that is ok by calculation? Now that would cost you a lot and it may not be possible without physical testing. Try and seek out an alternative if you can.. do one of your great 3D models as can't quite picture what you intend at your end. Simpson et al have a huge range of bracketry so keep looking and you may find one that fits the bill.. with some load data tables.

Good for you. There is lots to learn, but if your approach it in the right way it can be great fun, personally and financially rewarding. Have you had a look at your permittted development rights? You probably have but that is a good starting point. Even if you don't comply they help you identify where you don't and that leads you to the next step as to what you need to do to remain compliant with the regulations. Where are you in the UK as PD rights differ.

Spot on. The truss I show needs some adaptation to make it cost effective for the light loads and thin heavily insulated walls that you encounter in a domestic job but with a fair wind an a bit of lateral thinking / understanding of this type of structural truss it can be the perfect solution on occasion. It's not an unusual concept as we use this from time to time on tall buildings and you see it all the time on motorway foot bridges etc. One of the big costs of these type of trusses lie in the welding cost. No fancy welds that need tested (keeps in the realm of the local fabricator), also don't skimp on the steel section wall thickness at the early design stage as later you could get tripped up when you come to the do the energy performance calculations. Would be interested in hearing what you SE pal has to say and if said has a better idea.

Well that's a good start! To keep you on the right side of things below are the design loadings from BS 6180 for domestic internal stairs, landings etc. Your on the top line. Often the governing load for the hand rail is the horizontally uniformly distributed load of 0.36 kN/m (~36 kg per metre run of hand rail) and this load usually get transferred to the top of the hand rail. An important point here is that these are unfactored loadings.. thus no factor of safety built in. The other important bit is the deflection of the overall asssembly, from the same code The 25mm deflection is a key requirement. If you want have a test of what you have. Take your hand rail length just say 3.0m and calculate the horizontal force at the top from the hand rail 3.0m x 0.36 kN/m / 2 = 0.54 kN (~54 kg) Get a spring scale ( for weighing fish or something) and apply that load to the top of the uni strut. See how much it deflects by < 25mm Next test for strength using the Eurocode factors of safety. Take the 0.54 kN load and and multipy by load factor of 1.5 = 0.54 x 1.5 = 0.81 kN ~ 80kg Also make an allowance for material defects that may manifest later. Apply a material factor of 1.3 thus 80kg x 1.3 = 104kg ~= 1.02 kN test load. Two things to remember. You are testing the newal post in isolation here and I'm not taking into account the potential bracing effect of the handrail running perpendicular to the newal post down the sloping part of the stair. Some may and rightly say.. it's always stiffer than that once you put things together. I say.. your often right but can you imagine how hard that is to prove? and also you can often shift the problem somewhere else if you shed load from the newal post. On the other hand 104 kg is about 16 stones.. there are plenty folk that are heavier than that.. and if you have a Rugby team partying, a couple of big lads could push the thing close to its design limits. Report back.. check the deflections first in case the strut fails early.

Good to see we have both identified how flexible the rod appraoch can be. The zip bolts work in a different way I suspect where they work in tension and the edge of the newal post is compressing against something solid... but few things are that "solid" and often your bog standard stair is far from solid. I made a post a while ago about the forces that you encounter when designing glass ballustrades.. they are significant.

@ETC interesting detail, thanks for providing.

Heads up.. darkest hour is before dawn etc.

A 16 dia rod is too bendy. The amount it will flex is related to it's second moment of area Ixx = pi *radius^4 / 4 = 3.142 x 16*16*16*16/4 = 51478mm^4 A 40 x 40 x 5.0mm thick SHS section of has a value of Ixx = 134000mm^4 134000 / 51478 = 2.6 = about 260% stiffer than the rod. A 50 x 50 x 6.3mm thk section 328000 mm^4 328000 / 51478 = 6.3 = about 630% stiffer than the rod. You can see from the above why I mentioned a 50 x 50 section as being something that looks promising. For handrails and the like we need them to not just be strong enough but "feel strong and stiff" to the touch.

That's the easiest way!

You could do it with the lugs and bolt. I would need to check if 40 x 40 would still work, probably would but not going to say yes without checking. But there is an argument to be made that it is braced both ways by the handrail? .. but then the lower post needs to do more work... technically. The lug welds on the inside will foul the underside of the top flange of the beam. It looks like the beam you have could cope with having a "scuff" taken off the under edge of the top flange locally to let the SHS sit in tight. M10 grade 8.8 bolts should be fine. Mind you I would add a lock nut with a touch of Araldite glue to make sure they don't come lose later. Cut a piece of wood the exact lug spacing you need and take that to the welder. They will use it as the template. I think they will clamp the lugs to the timber and then weld them to the SHS... or something like that. A tip.. the bolts are 10mm nominal diameter. The holes usually 12mm nominal to allow for fabrication tolerances. Squeeze the glue in and around the bolt to fill in the gaps. From memory Hilti do a system like this where you flood the thing with resin so there is no slip.

It's a bit whacky for a domestic building but you can use what is called a Vierendeel Truss embeded in the inner leaf / as the structural frame . The base sits about the level of the ground floor ceiling... still in the insulation envelope, the top carries the roof loads. There is a bit of a cold bridge in terms of the inner skin but you can compensate for that by using insulated plaster board etc and treating the steels a bit like the inside of a window frame. You can then use a shelf angle to support the outer skin. Now if you have a 9.0m span this could be economic. But the shelf angle introduces a nasty twisting effect into the truss so you need to span the first floor joists perpendicular to the truss and use the joists and their connections to resist the twisting effect. It all takes a bit of thought and you need to get a grip on the how this type of structure behaves early on. If you plan it right it can be a very elegant way of doing it. These frame are usually made from square box section steel but for this span and the relatively light loads it needs to carry the section sizes can be quite modest with a bit of discrete stiffening. The above is a basic one but in a fair wind you can adjust the vertical struts a bit to coincide with the internal walls and window openings. The other main issue is lateral stability of the building. I can't make any more meaningful comment without seeing some floor plans etc.

That's a pig of a detail! Thanks for thinking of me. Questions.. 1/ Is there any risk of you making the effective width of the stair to narrow? probably not but check anyway. 2/ Is that a glass ballustrade or just a sketchup thingy? 3/ What are dimensions of the newal post? Would this concept work? It sounds a bit odd but on occasion we embed steel in timber.. like fish plates. Say the newal is 80 x 80mm Get a bit of 50 x 50 x 6.0mm SHS box section and weld that to the top of the steel. Make it extend 2/3 of the height of the newal post and get it bang on plumb. You may need to check the box section and carry the leg down to the botttom flange.. will take time but it should work. Cut a chase in the newal post say 51 - 55 mm wide x 60mm deep so it fits over the box section. You could resin (maybe use a slightly flexible construction adhesive) it in or secret screw it. I would go for resin / adhesive as the screw penetration will be small. Then fit a ~ 10mm cover piece to hide the steel and give it a bit of a sand, it will test your marketry skills but could be fun! Now you still have plenty meat of timber at the top at the top to fix the handrails etc. You'll know but few folk will spot it as the eye is drawn to the ballustrade / glass / spindals especially as the chase is cut on the top landing ballustrade side and not facing into or down the stair. Now you can check the post as much as you like below the level of the top of the steel to get the visual appearance you want. The 6.0mm thickness is partly so you don't burn through the section when welding and mucking about. To add a bit.. using the SHS up to two thirds height means that you reduce the bending force in the timber where the timber is thin by ~ 2/3 compared with having thin timber at the bottom subject to all the bending forces and the associated onerous forces on the fixings.

The founds are not that deep. Don't forget that the top of a found tends not to be quite as flat as you may hope for. You could maybe get one course of block on the top of the found but I would wait a bit until you see the found cast and check the levels, especially if you have any steps in the found. One way is to use concrete comon brick to level the coursing before you use the more expensive facing brick. If you don't use all the concrete commons they are very handy thing to have lying about anyway. Good spot @ETC I'm guessing so correct me if wrong. Away from the cranked vent you normally run the timber frame (TF) vapour barrier (not shown on your detail as it at a larger scale) down past the timber so any condensation runs down into the cavity and into the ground. But the cranked vent partially blocks the cavity. Also when the brickies work they inevitably drop some mortar down the cavity which lands on top of the cranked vent and bridges it. This could lead to the bottom rail of the TF and sole plate being exposed to damp locally. To solve this where you have cranked vent you introduce a bit of DPC which acts like a cavity tray. The vertical leg of the DPC goes up and behind the vapour barrier, the horizontal leg goes over the cranked solum vent so any water coming down the cavity gets directed away from the timber.

Hi all and thanks for the input, much appreciated. Nice idea, will consider. Yes it's been looked after, was completely redone I think circa mid sixties and maybe again after that.. but no one seems to know for sure. Not an option in this case, need to work with what is there. The truth will set you free! ..but thanks for being sensitive. As above. There is a suggestion that it may be a gypsom based product thus asbestos is not a problem. Futher investigation is in hand... hopefully it will be a false alarm. Client's Indead, listed building consent application in hand, there is no charge in Scotland.. one of the few things that are free these days. Will report later as project progresses. Thanks again all.