New Garden Outbuilding Advice

Hi Guys First of all thanks for a great forum. I've been lurking here for longer than i care to admit and it has an astonishing wealth of information. This is my first post so I hope i have covered the basics and haven't ovelooked minimum requirments before posting. I have a space in my back garden of 6.5M x 4.5M. I'm still coming up to speed on CAD tool so i have no drawing yet, nut its basically part lawn/part mud right now!. The garden is in a reidential area with neigbours within 20M of the graden. Also i live at the end of the street and so there is a culdesac road on one side of the garden I'm considering my design based on "Scotts Studio" (which i believe is related to the small studio.skp file from John) My budget is probably going to be aroung £10K - £15K GBP and my goal is to provide a home studio for myself and my eldest son. Volume levels would be "normal" for a control room. ie i dont want to annoy neighbours and i also dont want the local youth and there loud exhausts to annoy me either. I dont envisage a rock band being able to get in the studio all at once but there could be the odd occaison when indicual instruments (ie drums / bass / or guitar etc) could be tracked. So here are my questions to help me with the planning stage, and i post this in the construction forum but please redirect if you think it should be in the design forum... I'm trying to decide what material to use for the outside walls of the structure. As i see it I have two options:- 1. Classic Brick outer face single wall or cavity wall 2. Wood frame with outer shiplap cladding of either wood or stone As far as i can tell, if i go for the cavity brick wall approach then building an internal wall from studding, that gives me a 3 lief system which is not good (material & money) but my initial thoughts are that a brick/block cavity wall would give me more mass. Is this assertion correct ? The downside is more expense in both concreate footing & skilled labour. If I chose wood frame approach, I would essentially need to ensure the external facing side has enough mass prior to fixing finishing surface i guess ? Also, I anticipate that concreate haunches would not need to be 1M+ depth ? If there are threads that discuss this, that great and i'm happy to accept the links and read them :wink: Many Thanks John

Welcome to the forum! Actually, a hollow concrete block wall alone is not two leaves as previously posted, so you're not looking at a three leaf system. Obviously a concrete block wall flled with sand or concrete is better because of the additional mass. Are you under any municipal restrictions that would prohibit your erecting a building on the area you're planning? Here in my part of Sacramento, we have mandatory setbacks that prohibit building less than 5 feet from the side and 12½ feet from the rear property lines. --Keith :mrgreen:

Hi Keith Thanks for the response There are two sets of restrcitions in the UK and then local councils can apply local policies. the two restrictions are planning and building regulations The planning restrictions for my authority are:- 1. the use of the structure must be incidental to the enjoyment of the dwellinghouse 2. the structure is not positioned nearer to the highway than the original dwellinghouse 3. the floor area of the structure does not exceed more than 50% of the total area of the curtilage (excluding footproint of house) 4. pitched roof does not exceed 4M I've had confirmation from the local planning authority on the above. Building Regulations are also an important aspect and providing the following is true then it MAY not come under regulation. Thats what i will be checking next with my authority. 1. structure is not more than 30M^2 2. Is single story 3. Is detached 4. Contains no sleeping accom 5. Is constructed using substantially non-combustible materials (i.e. walls made from bricks or blocks, and a tiled pitched roof or flat roof. Timber roof joists are allowed.) If structure is made from wood or another combustible material then the structure must be situated at least 1 metre from any boundary. I'm planning to be 1M from boundary regardless but will confirm how likely building regulations requirement for my structure. So the question in my mind at the moment, before i contact building regulations, is should the strucutre be built from brick or block externally or should the structure be built from wood frame externally. thx

1st if you haven't already been check out Johns STC Chart Note: 8" Concrete Block, hollow core, no wall finish = STC of 45 by itself. Standard house brick unrendered. = STC 39, 45 if you render/stucco Brick Veneer construction with a layer of 16mm (5/8") plasterboard. That's one layer of 5/8" gypsum board attached to 2x4 frame, with insulation) = STC 56. All of the above will also have different TL numbers not necessarily corresponding to the difference in STC. Presuming by "cavity brick" you are referring to standard 8" x 8" x 16" (well really 7.5x7.5x15.5") concrete block or commonly referred to as cinder block (CB), I would say NO for that option, because of lower STC and the amount of real estate the CBs take up especially if you were to consider adding a 2x4 wall for inner frame. As Sharward noted hollow CB are (now, may always have been) considered 1 leaf. I am very guilty of advising and posting about CB and 2x4 wall system making 3 leafs, Knightfly told me this, I believe Eric Desert corrected us both on this... basically the concrete is to stiff to act as 2 leafs, bounce air and amplify sound as 3 leafs would. CB's should equal the mass of 4 layers of 5/8" drywall/gypsum or a number real close. If I had the option between 2x4 outer/exterior wall and regular brick, for sound isolation I would choose brick, IF I could afford it. The 2x4 wall is going to require a lot of beefing up to get it's mass equal to that of standard brick. Also in comparison to footing required for brick or 2x4 wall I don't think it's that big of a difference. Your still going to need a footing regardless. Here in Florida the same footing (basically) is required for 2x4 walls as CB because of wind sheer, the footing needs to hold the wall and house down/not let it blow away during a hurricane... I'm sure you won't have as strict wind codes, just thought I'd mention it. My wild A$$ guess is the only additional cost for footing would be a tiny amount more concrete and maybe re-bar. The real big difference in cost would the wall BUT with 2x4 you're going to have to factor in the "beef" of additional layers of sheathing, gypsum in stud bays, adding render/stucco to the exterior AND/OR another method of getting the mass of the 2x4 exterior wall equal to brick. SO if I could afford it, in your situation I would go with brick AND when making those footings I would make them wide enough so that new inner 2x4 wall rest on them. I'd make a monolithic slab (whole slab and footing= 1 pour), not pour the slab separate from footings. Hope this helps, and remember I am not an expert :D Marc

guitardad72 wrote:

SO if I could afford it, in your situation I would go with brick AND when making those footings

Marc, If it were me - I would avoid this - although it has a good STC rating - in order to install a brick veneer - it is required that the brick is bonded back to the structure behind it - the brick itself is not structurally capable of standing up all by itself...... Thus - for frequencies in the STC range it's fine - BUT - for low frequencies you loose a lot due to the coupling between the wall assemblies - flanking takes over. If it were a perfect world - I would use hollow core 8x8x16 (nominal) blocks - install rebar and grout as required for stability - and then fill the remaining cores with dry sand - prior to installing my bond beam to finish the top of the wall......... dry sand is an excellent damping agent - and raises the LF value of the assembly tremendously. I would then build my room within a room without ever connecting the 2 structures. In new construction - I would ALWAYS opt to construct in such a manner as to uncouple the slabs from the outer walls and foundation - thus i would not install a monolithic slab/foundation. Just my .02 cents......... SIncerely, Rod

Thanks Guys Actually i hadn't even considered the option of hollow core blocks filled with sand. I assume that i could then fix an outer cladding of some type which would be preferable to rendering. Or could i also use house brick to match the local stuctures ? Point taken on the footings requiring essentially equivelent for either brick or timber. I'm planning to got for an Isolated Concrete slab as per Rod's book. As far as building regs are concenred here, the minimum depth would be 500mm for the haunches and 150mm for rest of slab. my ground type is heavy clay. I will check this with the local authority to ensure this done right from the start Many Thanks John

Keep the questions coming. Can't wait to see this come together. 8) FYI, Marc, I believe "CB" stands for "Concrete Block," which is different than "Cinder Block." "Cinder blocks differ from concrete blocks in their aggregate content. Cinder blocks are made from coal cinders and portland cement. Cinder blocks are lighter and, depending on aggregate availability, may be cheaper than concrete blocks of the same size." (Source) I'm pretty sure that what we see (and mean) most often is concrete block, not cinder block. --Keith :mrgreen:

Sharward, I'm not going to take the time to find the source but I know I read something somewhere saying concrete block was the same thing as cinder block... urh.... still learning to not believe everything I read. Rod and JohnP, I suggested brick based on the STC numbers (not knowing TL), not having any knowledge of brick veneer build method and more of base on JohnP description of isolation goal:

Volume levels would be "normal" for a control room. ie i dont want to annoy neighbours and i also dont want the local youth and there loud exhausts to annoy me either. I dont envisage a rock band being able to get in the studio all at once but there could be the odd occaison when indicual instruments (ie drums / bass / or guitar etc) could be tracked.

Normal and recomended volume for a control room is 85dB. I'm perceiving JohnPs goal as slightly better then my goal which is STC 65, TL of -30dB at 50hz which I'm doing via double frame walls with 2 layers (or better) of 5/8" drywall or equivalent (or better) mass each wall. I may exceed my goal if I don't screw anything up. Guessing JohnP might go for 3 layers of drywall per leaf or: John could you give us a STC and TL goal? Also monolithic slab was suggested based on perceived isolation goal and because it's a lower cost. Still learning and still posting :twisted: Marc

Hi Guys Its been a long while since i last posted to this thread so sorry for that, but i have been here all the time literally reading many many other threads and doing a lot of other research...as well as start digging my trenches and draining them.. and then drooling over Lou's thread!! So i've submitted building notice for essentially 8" hollow block structure filled with sand. Does this in fact need to be kild dried sand or would "dried" sharp(builder) sand be ok ? My current plan: - 8" Block covered with membrane and timber cladding on outside. - Walls: 50mm airgap -> 100x50 studding (4"x2") with Rockwool RW3 -> 2 or 3 layers of 12mm plasterboard and greenglue - Floor: 150mm MOT1 tampled hardcore -> sand -> membrane -> celotex insutation -> 150mm reinfoced slab -> acoustic membrane -> finish (wood TBD) - Celing: joists 400mm centre on double header plates on wall frame. 100mm RW3 -> 2 or 3 layer of 12mm plasterboard and greenglue - Roof: 17.5 degreee pitch standard concrete tiled. Joist on 400mm centre on wallplate on hollow block Does this sound like a plan ? Next action for me is to "beef up" sketchup skills so i can get a damn pic up here...or photocopy architect drawing and create gif!! Eitherway, when i get final building approval, pics will follow :wink: