Do I need an Architect for an Garage/Pool Outbuilding?

[Nickfromwales]

2 hours ago, SBMS said:

That’s interesting… does that mvhr unit not pull in outside air and extract indoor air?

quoted from the link you provided. 
 

“This unit is speed controllable with the facility to reverse the supply air fan and provide 'double extraction' for periods when heat loss is desirable.”

[SBMS]

1 hour ago, Nickfromwales said:

quoted from the link you provided. 
 

“This unit is speed controllable with the facility to reverse the supply air fan and provide 'double extraction' for periods when heat loss is desirable.”

Got You - but that’s not its normal mode of operation? That would just be a mode to put it in extract only?

[SteamyTea]

As the pool building is quite large, can you not make your own MVHR unit.

Stainless steel has a conductivity of around 20W/m.K.

A 3mm thick sheet would have a U-value of 6.6 kW/m².K (I think: U=1/(thickness/conductivity).

With only a few metres of area and a relatively slow airspeed you could shift quite a bit of energy into the incoming air.

Probably only need a couple of relatively cheap, variable speed, fans and the controls could be manual after a bit fiddling.

[Nickfromwales]

13 hours ago, SBMS said:

Got You - but that’s not its normal mode of operation? That would just be a mode to put it in extract only?

Yes. And then you’d need the equivalent volume of incoming air available, via a transfer grille to outside, to allow that mode to be used effectively.

 

The transfer grille can be a motorised damper which is used when the MVHR is in double extract mode, or otherwise it can remain closed to allow the MVHR to function in push / pull (normal) mode.

 

What are your plans for space heating of the pool hall? Water usually sits at 30° or slightly above, so the pool hall will need to be higher than that to not make it feel

cool or cold to bathers. UFH obvs not the best idea there. 

 

You need the garage and the pool hall to be two separate compartments, if using chlorine, and store the chlorine in an outside store and NOT in the garage.

 

 

[SteamyTea]

23 minutes ago, Nickfromwales said:

UFH obvs not the best idea there. 

Quite a lot of commercial pools have UFH as it helps to keep the floor dry, less slippy, and therefore safer.

[phykell]

On 08/11/2025 at 12:38, Nickfromwales said:

The last one (indoor 15x5m) we were involved with was detailed in ICF, have you considered this? And also UFH pipes in the structure to reduce the size of plant etc.

 

Next one we’re quoting for is an outdoor, 15x5m again, and looking at ICF again for that one but with a bit more insulation layered under / around, and a bloody good motorised cover. 
 

Last indoor one we did I fitted a Recotherm 25+ air handling & dehumidification unit, which seemed a good bit of kit. 
 

We have specified large MVHR units for smaller pools (and tighter budgets) which seem to work quite well; caveat is the fans tend to need changing more frequently with those.

 

You should have an AHU which allows you to create a deficit of air pressure in the pool hall, so air naturally gets drawn into that area vs possibly finding its way ‘out’. This helps preserve build fabric and the Ferrari. 
 

Im a merc guy myself 🇩🇪 🚗 💨 

I've been watching a series of YouTube videos by a guy doing an outside pool using ICF. And then there's Robin Clevett's channel and his garden room, incorporating an indoor pool. I'd be interested in seeing comparisons between the various methods but I'll probably have to choose the judgement of the pool company I end up using. As it stands, there's already an 11m x 5m pool which is built in concrete with, I presume, zero insulation. I had thought I could possibly utilise part of it as the new pool but I'm not so sure now - insulation is going to be key to having a reasonable running cost, even with a ton of solar panels forming the roof. 

 

I see a lot of remarks about standard MVHRs not being up to the task as you suggest so that RecoTherm does sound interesting - no pricing on their website though and I couldn't find anything regarding sizing either. 

 

Next, I have to consider the building construction method - SIPs, timber frame or brick/block, but I'm leaning towards timber frame at the moment and stil trying to work out which would be more suitable to house a pool and a garage.

I'm just hoping everything will be done this time next year.

 

No Ferrari - not really into cars, prefer motorcycles 😎 

[SteamyTea]

3 minutes ago, phykell said:

leaning towards timber frame

Make sure all nails, screws, bolts and brackets are corrosion proof.

[Nickfromwales]

5 hours ago, SteamyTea said:

Make sure all nails, screws, bolts and brackets are corrosion proof.

Levels of chlorine for a domestic pool are only a few notches up from drinking water tbh. 

[SteamyTea]

10 minutes ago, Nickfromwales said:

Levels of chlorine for a domestic pool are only a few notches up from drinking water tbh. 

Were you on the material spec team for Pellikaan when they built St. Albans Leisure Centre, within a few weeks they had to rebuild the place.

Not sure what pools you go in, possibly brominated ones that smell a little less, but still corrosive, or ones where the pH is too low and it is converting the chlorine to Hypochlorite.

People think swimming pools are easy to look after.

 

Some random pictures.

 

 

 

 

 

And the classic.

 

 

[SBMS]

8 hours ago, Nickfromwales said:

Yes. And then you’d need the equivalent volume of incoming air available, via a transfer grille to outside, to allow that mode to be used effectively.

 

The transfer grille can be a motorised damper which is used when the MVHR is in double extract mode, or otherwise it can remain closed to allow the MVHR to function in push / pull (normal) mode.

 

What are your plans for space heating of the pool hall? Water usually sits at 30° or slightly above, so the pool hall will need to be higher than that to not make it feel

cool or cold to bathers. UFH obvs not the best idea there. 

 

You need the garage and the pool hall to be two separate compartments, if using chlorine, and store the chlorine in an outside store and NOT in the garage.

 

 

Am using UFH - why is this not ideal? Sorry I am not the OP re the large garage/ pool. Mine is a 10mx6m pool hall with a ln 8x3m in ground swim spa in it. 

[Gus Potter]

 

On 07/11/2025 at 17:55, phykell said:

The question is, where do I go from here?

 

On 08/11/2025 at 10:39, phykell said:

The size is approximately 29m x 7m. It would have been even bigger if I'd been able to build over the existing external swimming pool but it's too close to the neighbour's boundary so the pool has to be reduced in width.

 

 

Hope this helps. 

 

The design of these things needs to start with the ground. This is a large investment. One way of thinking about this is not just in terms of the weight of the structure on top, nor the weight of the pool when it's filled with water, as water often weight less than the soil you dig out, but what happens when you want to empty it for maintenance.

 

If the ground water is high then the "pool box" is going to float out the ground, we call this buoyancy. Just say your overall excavation with insulation under the base of the pool is 2.2m. The buoyancy will be about (very roughly) (29m + wall insulation, say 29.5m) x (7.0 + wall insulation, say 7.5m) x 2.2m (pool depth + floor + insulation) = about 487 tonnes! From that you deduct the weight of the walls below ground + the wieght of the structure on top. The type of structure you have is not likely to be heavy enough.

 

OK, you may say, well I'm going to dewater it when I want to empty it. But as you're close to the neighbours the dewatering may cause a problem over the boundary or cause a problem with the existing house.

 

Then, as others have pointed out, you have a chlorinated liquid in a building which is not a great fit with many common building materials.  

 

This takes time to think through and you do need good professional advice. 

 

 

 

 

 

 

[markc]

I have been in a few jobs where the piles under a pool were to hold it down, not up. Many of the boat shaped fibreglass pools have recommendations to build the earth around then rather than plant them in the ground.

[phykell]

16 hours ago, SteamyTea said:

Were you on the material spec team for Pellikaan when they built St. Albans Leisure Centre, within a few weeks they had to rebuild the place.

Not sure what pools you go in, possibly brominated ones that smell a little less, but still corrosive, or ones where the pH is too low and it is converting the chlorine to Hypochlorite.

People think swimming pools are easy to look after.

I'm working on the basis that a domestic pool's chlorine levels don't have to be anywhere near that required for a public pool and, typically, only two people will be using it regularly.

 

I'm told that an auto-dosing systems will monitor the water and only introduce as much chlorine as necessary. Option for chlorine to be reduced still further using a hybrid systems and there's even a mineral water alternative (with other issues). 

[SteamyTea]

2 hours ago, phykell said:

told that an auto-dosing systems will monitor the water and only introduce as much chlorine as necessary

Same sales pitch happening then.

A pool is a lot of work.

[Gus Potter]

8 hours ago, phykell said:

I'm working on the basis that a domestic pool's chlorine levels don't have to be anywhere near that required for a public pool and, typically, only two people will be using it regularly.

Thanks for posting, its a refreshing topic. 

 

Fundamentally, on the face of it, what you are doing is not that difficult.. the technology and designs are well proven. Where it becomes difficult is when folk don't reasearch or question the advice they are getting. But you are, so hat off to you. 

 

For me (SE hat on) I would want to understand the Architectural design; how is it supposed to work, how is it supposed to look, how does it marry with the house, garden and how does the space get use in terms of circulation, when you have a party / entertain. Then delve down and look at the choice of materials and why they have been selected Architecturally.

 

Once I get a handle on that then I can start to think about how you engineer that to stay within the Architectural envelope and material choice you the Client desires. 

 

11 hours ago, markc said:

I have been in a few jobs where the piles under a pool were to hold it down, not up.

This is common when you have a high water table. The piles more often than not are not subject to a lot of tension in normal use, but if under designed with a high water table then the middle of the pool slab can tend to lift up first when you fully empty it. This causes cracking which over time leads to leaks and so on. This gets worse over time, but by then the contractor is long gone. Then if things are bad the whole building can float up and out of the ground!

 

Tension piles and restrictive maintenance clauses can vary, in other words pool design can be a bit like the second hand market, prices can vary a lot, so you have to be really careful that what you are buying is going to do the job you want with the life span you want. 

 

When we have chlorine SE's will usually err on the safe side and treat this as an aggresive environment. The thing is that while you may control it the next owner may not. This comes under our Civic responsibility. At some point you may want to sell the house, a surveyor may say.. how much is this pool going to cost to maintain over the next 40 years. If there are too many caveats then it may put a buyer off. The extra cost of protecting your asset is often not as much as you think. 

 

For me I'm interested in your ground conditions.

 

@markc knows a lot about this stuff, probably more than I! 

 

Keep up the good work posting!