Ian

You've got 2 main issues that need resolving: ensuring the screed is dry enough (it needs to get down to 75% RH) ensuring the screed is properly prepared ready for the final floor finishes. (If you are planning to stick anything down onto the screed like the bamboo the screed will need the surface laitance removing)

sand cement screeds and concrete slabs are much more forgiving than anhydrite type screeds and typically need less work to remove laitance prior to tiling. You still need to remove any laitance however there will be a lot less of it compared to anhydrite screeds. The reason for this is that anhydrite screeds contain far more water which is why the laitance is more prevalent. The main issue with power floated slabs is that the power floating process seals the surface of the concrete making the drying process much longer. In fact I would say that 12 months drying time would not be unusual for a power floated slab. The good news is that there are plenty of liquid dpm products that can be applied to the top of the slab to get around this problem however they are not cheap.

With a click fit type floor you wouldn't need to use adhesive to stick the floor to the screed which makes the while process much simpler however you still need to ensure the screed is properly dry, or alternatively, use one of the special loose underlays that allow any residual moisture to escape to the edges of the floor.

@MJNewton It's very common on large commercial buildings that use single ply membrane roofs (membranes like yours) for the membrane to be laid completely flat for example along very long and wide gutter runs (most large new Tesco stores are done that way) so IMO there's absolutely zero chance of your roof leaking due to a slightly shallower angle of fall than the 1:80 recommendation. It sounds like your builder is one in a million! If it were my roof I'd definitely go with option 1. I'd agree with your builder that Option 2 carries a risk of creating unintended damage elsewhere which might mean that you end up with a worse job than the original. Option 3 carries a significant risk of creating a problem with interstitial condensation in the zone between the 2 roof skins.

advice from BAL is here: https://www.bal-adhesives.com/tiling-onto-calcium-sulfate-anhydrite-screeds/ Edit: Also this advice from Sika: "Calcium Sulphate screeds will not normally start to dry properly until the laitance have been removed. The sooner this process is done the easier it is to eradicate. This is normally the responsibility of the screeding contractor who is best placed to know when the screed has cured sufficiently to proceed. The conditions on site and the thickness of surface laitance play a large part in the drying times that will be required. As a general rule of thumb if the laitance are removed at the end of the 1st week of placing a light sanding action is all that will be needed. In the 2nd week a courser aggregate maybe required. In weeks 3 and 4 you may well require a rotary carborundum stone or a heavy weight diamond grinder. In short, the longer the laitance are left the denser they become and more difficult they are to remove. Once the laitance are removed Calcium Sulphate screeds dry similarly to that of sand/cement, which given the optimum conditions is 1mm per day up to 40mm thick and an additional 2 days per 1mm over this thickness."

You'll have no problems if you just want to switch the pump off for an hour or so while you're sitting outside.

My blower treatment plant is in a holiday home and I was told by the manufacturer to put it on a timer - 2 hours on/2 hours off BTW - are you getting more noise from the chamber or from the pump? With us, the pump is housed in a separate brick built housing on a concrete base (it's about 10m from the treatment plant). The pump has rubber feet and it is almost silent in use with the door shut. I get more noise from the treatment plant itself but even with that you have to be standing within 3 or 4 metres of it to hear it.

normally they would tell you at what point in the build process they need to inspect. It's usually: - foundations - drainage connections -pre-plaster - completion

Facade designs which use a ventilated rainscreen are a safer option compared to the one you’ve just described. Try reading this link about the problems experienced in Canada: https://en.m.wikipedia.org/wiki/Leaky_condo_crisis and the same design related issue in New Zealand: https://en.m.wikipedia.org/wiki/Leaky_homes_crisis

I presume that you’ve had some wet weather since the roof was finished? If so, does rainwater pond anywhere on the roof or is it ok? The British Standard is not a mandatory requirement. The reason for stating that there should be a minimum design fall of 1:80 is because with falls that are shallower than that it’s easy to end with flat spots in the roof which hold water.

good idea on using the step to double up as a seat! I'm so pleased to hear that it's working out as well as you'd hoped with bookings! Ian

Great link by @Onoff just one thing to add is that you’ll need sign off from either (a) the HETAS fitter or (b) the Building Inspector so make sure you ask discuss your proposals with them in advance

we had a client who insisted on using limestone for the walkway around a new internal swimming pool on a £5M house extension. This is usually a big No-No for obvious reasons but the wife was insistent and wouldn't listen to technical reasons. We had the limestone sealed and wrote to the them with advice regarding maintenance.

@Dreadnaught its easy to design private sewers that comply with the guidance laid out in the approved documents of Building Regs but it doesn’t always follow that you will then be granted permission to connect these to a public sewer. Separate from Planning Permission and Building Regs approval there is a also a formal application that you must submit before you are allowed to make a connection to a public sewer. I’m working on a commercial project at the moment where UU are refusing our client permission to connect the site’s SW sewer to the public combined sewer in the road because the sewer in the road is already at its design capacity limit. Instead, they want our client to connect his SW sewer to a small stream that is located 400m away across a field that is not in our clients ownership.

Sorry, but i’ve got serious doubts that tanking the inside of the building will do anything at all. The answer is to find out how the water is penetrating past the external membrane and fix it at that location.

Water leaks like this can be a pig to trace where the water is getting in as it can sometimes track along horizontally for quite a distance until it finds a weak spot where it then enters the building. While the rooflight is off I'd do a water flood test to try and establish if the water is coming in from the sides of the upstands or not. Get a hosepipe and gently soak the area around the upstand whilst making sure the level of the water doesn't rise up past the top of the rubber. If you get new water entering the building then you will know its not the seal between the rooflight and the upstand.

@ProDave Air in the system somewhere?

If you are finding that the condensation and mould problems are worse in the bedroom then I think the gas heater will be the main cause of the problem. Gas heaters are notorious for causing problems with condensation as they emit large quantities of moisture vapour as part of the combustion process - v approx 1 litre of water vapour for every litre of gas. Have you considered using a de-humidifier as an experiment to try and control the excess condensation? Edit: forgot to say that as well as being great at reducing problems with condensation & mould de-humidifiers can be surprisingly efficient as heaters (better than 100% efficiency) and certainly more efficient than your electric fan heater.

It’s highly unlikely that you’d have a problem in a small area of screed like that. The risk areas are new floor slabs or screeds of a size of eg 6m x 12m where it’s highly likely that the slab would develop a crack in the middle of the 12m direction. If you have a floor finish on top that can’t crack such as vinyl or timber (or bamboo) then it’s not a problem as the crack in the screed below will never be seen. With inflexible ceramic or stone tiles however the risk is that they crack along the line of the crack in the screed below. That’s why decoupling mats are recommended.

No, they are all power floated concrete slabs reinforced with steel mesh.

Yes, 2 years is long enough even with a power floated slab. The easiest way to tell if your slab or screed has finished curing and therefore finished shrinking is to measure its relative humidity. The target value is 75% RH

+1 I agree completely with @nod All new concrete and screed will shrink and crack to some extent, even if it has reinforcing mesh. If you go into any large retail shed with an exposed concrete floor such as B&Q or Costco you will see that the floor has some kind of movement joint at approx 6 metre intervals in both directions. If there’s no designed movement joint then you’ll see a ragged crack (or sometimes both!) Older concrete and screed floors like @Onoffwill have finished with any shrinkage movement so anything you put on top should be okay if there’s no existing cracks.

@temp is correct and this is already applied commonly to Planning Permissions on commercial buildings to make the use of renewables compulsory above and beyond the requirements of the Building Regs

@PeterStarck all new bare (mill finish) aluminium will form a very thin and hard layer of aluminium oxide on the surface. That’s what gives it resistance to any further corrosion and it makes it highly durable

@hmpmarketing A caravan is not a building so is not subject to the rules for "Permitted Development". You wouldn't therefore need Planning Permission as long as there is no change of use of the land. If the caravan is incidental to the main house then it will not involve creating a separate dwelling so will be okay. Useful guide and free Pdf booklet here: http://www.valuemobilehomes.com/planning/